Merge branches 'doc.2021.07.20c', 'fixes.2021.08.06a', 'nocb.2021.07.20c', 'nolibc.2021.07.20c', 'tasks.2021.07.20c', 'torture.2021.07.27a' and 'torturescript.2021.07.27a' into HEAD
doc.2021.07.20c: Documentation updates.
fixes.2021.08.06a: Miscellaneous fixes.
nocb.2021.07.20c: Callback-offloading (NOCB CPU) updates.
nolibc.2021.07.20c: Tiny userspace library updates.
tasks.2021.07.20c: Tasks RCU updates.
torture.2021.07.27a: In-kernel torture-test updates.
torturescript.2021.07.27a: Torture-test scripting updates.
diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index f8633d3..d29740b 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -11,15 +11,6 @@
#include <linux/rcupdate.h>
/*
- * Why is there no list_empty_rcu()? Because list_empty() serves this
- * purpose. The list_empty() function fetches the RCU-protected pointer
- * and compares it to the address of the list head, but neither dereferences
- * this pointer itself nor provides this pointer to the caller. Therefore,
- * it is not necessary to use rcu_dereference(), so that list_empty() can
- * be used anywhere you would want to use a list_empty_rcu().
- */
-
-/*
* INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers
* @list: list to be initialized
*
@@ -318,21 +309,29 @@
/*
* Where are list_empty_rcu() and list_first_entry_rcu()?
*
- * Implementing those functions following their counterparts list_empty() and
- * list_first_entry() is not advisable because they lead to subtle race
- * conditions as the following snippet shows:
+ * They do not exist because they would lead to subtle race conditions:
*
* if (!list_empty_rcu(mylist)) {
* struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member);
* do_something(bar);
* }
*
- * The list may not be empty when list_empty_rcu checks it, but it may be when
- * list_first_entry_rcu rereads the ->next pointer.
+ * The list might be non-empty when list_empty_rcu() checks it, but it
+ * might have become empty by the time that list_first_entry_rcu() rereads
+ * the ->next pointer, which would result in a SEGV.
*
- * Rereading the ->next pointer is not a problem for list_empty() and
- * list_first_entry() because they would be protected by a lock that blocks
- * writers.
+ * When not using RCU, it is OK for list_first_entry() to re-read that
+ * pointer because both functions should be protected by some lock that
+ * blocks writers.
+ *
+ * When using RCU, list_empty() uses READ_ONCE() to fetch the
+ * RCU-protected ->next pointer and then compares it to the address of the
+ * list head. However, it neither dereferences this pointer nor provides
+ * this pointer to its caller. Thus, READ_ONCE() suffices (that is,
+ * rcu_dereference() is not needed), which means that list_empty() can be
+ * used anywhere you would want to use list_empty_rcu(). Just don't
+ * expect anything useful to happen if you do a subsequent lockless
+ * call to list_first_entry_rcu()!!!
*
* See list_first_or_null_rcu for an alternative.
*/
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index d9680b7..434d12f 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -53,7 +53,7 @@
* nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other
* types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
*/
-#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
+#define rcu_preempt_depth() READ_ONCE(current->rcu_read_lock_nesting)
#else /* #ifdef CONFIG_PREEMPT_RCU */
@@ -167,7 +167,7 @@
# define synchronize_rcu_tasks synchronize_rcu
# endif
-# ifdef CONFIG_TASKS_RCU_TRACE
+# ifdef CONFIG_TASKS_TRACE_RCU
# define rcu_tasks_trace_qs(t) \
do { \
if (!likely(READ_ONCE((t)->trc_reader_checked)) && \
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 953e70f..9be0153 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -14,9 +14,6 @@
#include <asm/param.h> /* for HZ */
-/* Never flag non-existent other CPUs! */
-static inline bool rcu_eqs_special_set(int cpu) { return false; }
-
unsigned long get_state_synchronize_rcu(void);
unsigned long start_poll_synchronize_rcu(void);
bool poll_state_synchronize_rcu(unsigned long oldstate);
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 0e0cf4d..6cfaa0a 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -61,7 +61,7 @@
int idx;
idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
- WRITE_ONCE(ssp->srcu_lock_nesting[idx], ssp->srcu_lock_nesting[idx] + 1);
+ WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
return idx;
}
@@ -81,11 +81,11 @@
{
int idx;
- idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
+ idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1;
pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
tt, tf, idx,
- READ_ONCE(ssp->srcu_lock_nesting[!idx]),
- READ_ONCE(ssp->srcu_lock_nesting[idx]));
+ data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])),
+ data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])));
}
#endif
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index b3adb40..7c5a4a0 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -59,7 +59,7 @@
static struct task_struct **reader_tasks;
static bool lock_is_write_held;
-static bool lock_is_read_held;
+static atomic_t lock_is_read_held;
static unsigned long last_lock_release;
struct lock_stress_stats {
@@ -682,7 +682,7 @@
if (WARN_ON_ONCE(lock_is_write_held))
lwsp->n_lock_fail++;
lock_is_write_held = true;
- if (WARN_ON_ONCE(lock_is_read_held))
+ if (WARN_ON_ONCE(atomic_read(&lock_is_read_held)))
lwsp->n_lock_fail++; /* rare, but... */
lwsp->n_lock_acquired++;
@@ -717,13 +717,13 @@
schedule_timeout_uninterruptible(1);
cxt.cur_ops->readlock(tid);
- lock_is_read_held = true;
+ atomic_inc(&lock_is_read_held);
if (WARN_ON_ONCE(lock_is_write_held))
lrsp->n_lock_fail++; /* rare, but... */
lrsp->n_lock_acquired++;
cxt.cur_ops->read_delay(&rand);
- lock_is_read_held = false;
+ atomic_dec(&lock_is_read_held);
cxt.cur_ops->readunlock(tid);
stutter_wait("lock_torture_reader");
@@ -738,20 +738,22 @@
static void __torture_print_stats(char *page,
struct lock_stress_stats *statp, bool write)
{
+ long cur;
bool fail = false;
int i, n_stress;
- long max = 0, min = statp ? statp[0].n_lock_acquired : 0;
+ long max = 0, min = statp ? data_race(statp[0].n_lock_acquired) : 0;
long long sum = 0;
n_stress = write ? cxt.nrealwriters_stress : cxt.nrealreaders_stress;
for (i = 0; i < n_stress; i++) {
- if (statp[i].n_lock_fail)
+ if (data_race(statp[i].n_lock_fail))
fail = true;
- sum += statp[i].n_lock_acquired;
- if (max < statp[i].n_lock_acquired)
- max = statp[i].n_lock_acquired;
- if (min > statp[i].n_lock_acquired)
- min = statp[i].n_lock_acquired;
+ cur = data_race(statp[i].n_lock_acquired);
+ sum += cur;
+ if (max < cur)
+ max = cur;
+ if (min > cur)
+ min = cur;
}
page += sprintf(page,
"%s: Total: %lld Max/Min: %ld/%ld %s Fail: %d %s\n",
@@ -996,7 +998,6 @@
}
if (nreaders_stress) {
- lock_is_read_held = false;
cxt.lrsa = kmalloc_array(cxt.nrealreaders_stress,
sizeof(*cxt.lrsa),
GFP_KERNEL);
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index dca51fe9..2cc34a2 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -487,7 +487,7 @@
if (gp_async) {
cur_ops->gp_barrier();
}
- writer_n_durations[me] = i_max;
+ writer_n_durations[me] = i_max + 1;
torture_kthread_stopping("rcu_scale_writer");
return 0;
}
@@ -561,7 +561,7 @@
wdpp = writer_durations[i];
if (!wdpp)
continue;
- for (j = 0; j <= writer_n_durations[i]; j++) {
+ for (j = 0; j < writer_n_durations[i]; j++) {
wdp = &wdpp[j];
pr_alert("%s%s %4d writer-duration: %5d %llu\n",
scale_type, SCALE_FLAG,
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 40ef541..ab421526 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2022,8 +2022,13 @@
__func__, raw_smp_processor_id());
while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
stop_at))
- if (stall_cpu_block)
+ if (stall_cpu_block) {
+#ifdef CONFIG_PREEMPTION
+ preempt_schedule();
+#else
schedule_timeout_uninterruptible(HZ);
+#endif
+ }
if (stall_cpu_irqsoff)
local_irq_enable();
else if (!stall_cpu_block)
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index d998a76..66dc14c 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -467,6 +467,40 @@
.name = "acqrel"
};
+static volatile u64 stopopts;
+
+static void ref_clock_section(const int nloops)
+{
+ u64 x = 0;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--)
+ x += ktime_get_real_fast_ns();
+ preempt_enable();
+ stopopts = x;
+}
+
+static void ref_clock_delay_section(const int nloops, const int udl, const int ndl)
+{
+ u64 x = 0;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ x += ktime_get_real_fast_ns();
+ un_delay(udl, ndl);
+ }
+ preempt_enable();
+ stopopts = x;
+}
+
+static struct ref_scale_ops clock_ops = {
+ .readsection = ref_clock_section,
+ .delaysection = ref_clock_delay_section,
+ .name = "clock"
+};
+
static void rcu_scale_one_reader(void)
{
if (readdelay <= 0)
@@ -759,7 +793,7 @@
int firsterr = 0;
static struct ref_scale_ops *scale_ops[] = {
&rcu_ops, &srcu_ops, &rcu_trace_ops, &rcu_tasks_ops, &refcnt_ops, &rwlock_ops,
- &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
+ &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
};
if (!torture_init_begin(scale_type, verbose))
diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 26344dc..a0ba2ed49 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -96,7 +96,7 @@
*/
void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
- int newval = ssp->srcu_lock_nesting[idx] - 1;
+ int newval = READ_ONCE(ssp->srcu_lock_nesting[idx]) - 1;
WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval);
if (!newval && READ_ONCE(ssp->srcu_gp_waiting))
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 8536c55..806160c 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -643,8 +643,8 @@
//
// "Rude" variant of Tasks RCU, inspired by Steve Rostedt's trick of
// passing an empty function to schedule_on_each_cpu(). This approach
-// provides an asynchronous call_rcu_tasks_rude() API and batching
-// of concurrent calls to the synchronous synchronize_rcu_rude() API.
+// provides an asynchronous call_rcu_tasks_rude() API and batching of
+// concurrent calls to the synchronous synchronize_rcu_tasks_rude() API.
// This invokes schedule_on_each_cpu() in order to send IPIs far and wide
// and induces otherwise unnecessary context switches on all online CPUs,
// whether idle or not.
@@ -785,7 +785,10 @@
// set that task's .need_qs flag so that task's next outermost
// rcu_read_unlock_trace() will report the quiescent state (in which
// case the count of readers is incremented). If both attempts fail,
-// the task is added to a "holdout" list.
+// the task is added to a "holdout" list. Note that IPIs are used
+// to invoke trc_read_check_handler() in the context of running tasks
+// in order to avoid ordering overhead on common-case shared-variable
+// accessses.
// rcu_tasks_trace_postscan():
// Initialize state and attempt to identify an immediate quiescent
// state as above (but only for idle tasks), unblock CPU-hotplug
@@ -847,7 +850,7 @@
/* If we are the last reader, wake up the grace-period kthread. */
void rcu_read_unlock_trace_special(struct task_struct *t, int nesting)
{
- int nq = t->trc_reader_special.b.need_qs;
+ int nq = READ_ONCE(t->trc_reader_special.b.need_qs);
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) &&
t->trc_reader_special.b.need_mb)
@@ -894,7 +897,7 @@
// If the task is not in a read-side critical section, and
// if this is the last reader, awaken the grace-period kthread.
- if (likely(!t->trc_reader_nesting)) {
+ if (likely(!READ_ONCE(t->trc_reader_nesting))) {
if (WARN_ON_ONCE(atomic_dec_and_test(&trc_n_readers_need_end)))
wake_up(&trc_wait);
// Mark as checked after decrement to avoid false
@@ -903,7 +906,7 @@
goto reset_ipi;
}
// If we are racing with an rcu_read_unlock_trace(), try again later.
- if (unlikely(t->trc_reader_nesting < 0)) {
+ if (unlikely(READ_ONCE(t->trc_reader_nesting) < 0)) {
if (WARN_ON_ONCE(atomic_dec_and_test(&trc_n_readers_need_end)))
wake_up(&trc_wait);
goto reset_ipi;
@@ -913,14 +916,14 @@
// Get here if the task is in a read-side critical section. Set
// its state so that it will awaken the grace-period kthread upon
// exit from that critical section.
- WARN_ON_ONCE(t->trc_reader_special.b.need_qs);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs));
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
reset_ipi:
// Allow future IPIs to be sent on CPU and for task.
// Also order this IPI handler against any later manipulations of
// the intended task.
- smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
+ smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
}
@@ -950,6 +953,7 @@
n_heavy_reader_ofl_updates++;
in_qs = true;
} else {
+ // The task is not running, so C-language access is safe.
in_qs = likely(!t->trc_reader_nesting);
}
@@ -964,7 +968,7 @@
// state so that it will awaken the grace-period kthread upon exit
// from that critical section.
atomic_inc(&trc_n_readers_need_end); // One more to wait on.
- WARN_ON_ONCE(t->trc_reader_special.b.need_qs);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs));
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
return true;
}
@@ -982,7 +986,7 @@
// The current task had better be in a quiescent state.
if (t == current) {
t->trc_reader_checked = true;
- WARN_ON_ONCE(t->trc_reader_nesting);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting));
return;
}
@@ -994,6 +998,12 @@
}
put_task_struct(t);
+ // If this task is not yet on the holdout list, then we are in
+ // an RCU read-side critical section. Otherwise, the invocation of
+ // rcu_add_holdout() that added it to the list did the necessary
+ // get_task_struct(). Either way, the task cannot be freed out
+ // from under this code.
+
// If currently running, send an IPI, either way, add to list.
trc_add_holdout(t, bhp);
if (task_curr(t) &&
@@ -1092,8 +1102,8 @@
".I"[READ_ONCE(t->trc_ipi_to_cpu) > 0],
".i"[is_idle_task(t)],
".N"[cpu > 0 && tick_nohz_full_cpu(cpu)],
- t->trc_reader_nesting,
- " N"[!!t->trc_reader_special.b.need_qs],
+ READ_ONCE(t->trc_reader_nesting),
+ " N"[!!READ_ONCE(t->trc_reader_special.b.need_qs)],
cpu);
sched_show_task(t);
}
@@ -1187,7 +1197,7 @@
static void exit_tasks_rcu_finish_trace(struct task_struct *t)
{
WRITE_ONCE(t->trc_reader_checked, true);
- WARN_ON_ONCE(t->trc_reader_nesting);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting));
WRITE_ONCE(t->trc_reader_nesting, 0);
if (WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)))
rcu_read_unlock_trace_special(t, 0);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 51f24ec..bce848e 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -74,17 +74,10 @@
/* Data structures. */
-/*
- * Steal a bit from the bottom of ->dynticks for idle entry/exit
- * control. Initially this is for TLB flushing.
- */
-#define RCU_DYNTICK_CTRL_MASK 0x1
-#define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1)
-
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
.dynticks_nesting = 1,
.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
- .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
+ .dynticks = ATOMIC_INIT(1),
#ifdef CONFIG_RCU_NOCB_CPU
.cblist.flags = SEGCBLIST_SOFTIRQ_ONLY,
#endif
@@ -259,6 +252,15 @@
}
/*
+ * Increment the current CPU's rcu_data structure's ->dynticks field
+ * with ordering. Return the new value.
+ */
+static noinline noinstr unsigned long rcu_dynticks_inc(int incby)
+{
+ return arch_atomic_add_return(incby, this_cpu_ptr(&rcu_data.dynticks));
+}
+
+/*
* Record entry into an extended quiescent state. This is only to be
* called when not already in an extended quiescent state, that is,
* RCU is watching prior to the call to this function and is no longer
@@ -266,7 +268,6 @@
*/
static noinstr void rcu_dynticks_eqs_enter(void)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
int seq;
/*
@@ -275,13 +276,9 @@
* next idle sojourn.
*/
rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
- seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
+ seq = rcu_dynticks_inc(1);
// RCU is no longer watching. Better be in extended quiescent state!
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- (seq & RCU_DYNTICK_CTRL_CTR));
- /* Better not have special action (TLB flush) pending! */
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- (seq & RCU_DYNTICK_CTRL_MASK));
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & 0x1));
}
/*
@@ -291,7 +288,6 @@
*/
static noinstr void rcu_dynticks_eqs_exit(void)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
int seq;
/*
@@ -299,15 +295,10 @@
* and we also must force ordering with the next RCU read-side
* critical section.
*/
- seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
+ seq = rcu_dynticks_inc(1);
// RCU is now watching. Better not be in an extended quiescent state!
rcu_dynticks_task_trace_exit(); // After ->dynticks update!
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- !(seq & RCU_DYNTICK_CTRL_CTR));
- if (seq & RCU_DYNTICK_CTRL_MASK) {
- arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
- smp_mb__after_atomic(); /* _exit after clearing mask. */
- }
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & 0x1));
}
/*
@@ -324,9 +315,9 @@
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR)
+ if (atomic_read(&rdp->dynticks) & 0x1)
return;
- atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
+ rcu_dynticks_inc(1);
}
/*
@@ -336,9 +327,7 @@
*/
static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- return !(arch_atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
+ return !(atomic_read(this_cpu_ptr(&rcu_data.dynticks)) & 0x1);
}
/*
@@ -347,9 +336,8 @@
*/
static int rcu_dynticks_snap(struct rcu_data *rdp)
{
- int snap = atomic_add_return(0, &rdp->dynticks);
-
- return snap & ~RCU_DYNTICK_CTRL_MASK;
+ smp_mb(); // Fundamental RCU ordering guarantee.
+ return atomic_read_acquire(&rdp->dynticks);
}
/*
@@ -358,7 +346,7 @@
*/
static bool rcu_dynticks_in_eqs(int snap)
{
- return !(snap & RCU_DYNTICK_CTRL_CTR);
+ return !(snap & 0x1);
}
/* Return true if the specified CPU is currently idle from an RCU viewpoint. */
@@ -389,8 +377,7 @@
int snap;
// If not quiescent, force back to earlier extended quiescent state.
- snap = atomic_read(&rdp->dynticks) & ~(RCU_DYNTICK_CTRL_MASK |
- RCU_DYNTICK_CTRL_CTR);
+ snap = atomic_read(&rdp->dynticks) & ~0x1;
smp_rmb(); // Order ->dynticks and *vp reads.
if (READ_ONCE(*vp))
@@ -398,32 +385,7 @@
smp_rmb(); // Order *vp read and ->dynticks re-read.
// If still in the same extended quiescent state, we are good!
- return snap == (atomic_read(&rdp->dynticks) & ~RCU_DYNTICK_CTRL_MASK);
-}
-
-/*
- * Set the special (bottom) bit of the specified CPU so that it
- * will take special action (such as flushing its TLB) on the
- * next exit from an extended quiescent state. Returns true if
- * the bit was successfully set, or false if the CPU was not in
- * an extended quiescent state.
- */
-bool rcu_eqs_special_set(int cpu)
-{
- int old;
- int new;
- int new_old;
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
-
- new_old = atomic_read(&rdp->dynticks);
- do {
- old = new_old;
- if (old & RCU_DYNTICK_CTRL_CTR)
- return false;
- new = old | RCU_DYNTICK_CTRL_MASK;
- new_old = atomic_cmpxchg(&rdp->dynticks, old, new);
- } while (new_old != old);
- return true;
+ return snap == atomic_read(&rdp->dynticks);
}
/*
@@ -439,13 +401,12 @@
*/
notrace void rcu_momentary_dyntick_idle(void)
{
- int special;
+ int seq;
raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
- special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR,
- &this_cpu_ptr(&rcu_data)->dynticks);
+ seq = rcu_dynticks_inc(2);
/* It is illegal to call this from idle state. */
- WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR));
+ WARN_ON_ONCE(!(seq & 0x1));
rcu_preempt_deferred_qs(current);
}
EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
@@ -1325,7 +1286,7 @@
*/
jtsq = READ_ONCE(jiffies_to_sched_qs);
ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
- rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
+ rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
if (!READ_ONCE(*rnhqp) &&
(time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
time_after(jiffies, rcu_state.jiffies_resched) ||
@@ -1772,7 +1733,7 @@
/*
* Initialize a new grace period. Return false if no grace period required.
*/
-static bool rcu_gp_init(void)
+static noinline_for_stack bool rcu_gp_init(void)
{
unsigned long firstseq;
unsigned long flags;
@@ -1966,7 +1927,7 @@
/*
* Loop doing repeated quiescent-state forcing until the grace period ends.
*/
-static void rcu_gp_fqs_loop(void)
+static noinline_for_stack void rcu_gp_fqs_loop(void)
{
bool first_gp_fqs;
int gf = 0;
@@ -1993,8 +1954,8 @@
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqswait"));
WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_FQS);
- ret = swait_event_idle_timeout_exclusive(
- rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j);
+ (void)swait_event_idle_timeout_exclusive(rcu_state.gp_wq,
+ rcu_gp_fqs_check_wake(&gf), j);
rcu_gp_torture_wait();
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS);
/* Locking provides needed memory barriers. */
@@ -2471,9 +2432,6 @@
WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1);
/* Adjust any no-longer-needed kthreads. */
rcu_boost_kthread_setaffinity(rnp, -1);
- /* Do any needed no-CB deferred wakeups from this CPU. */
- do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu));
-
// Stop-machine done, so allow nohz_full to disable tick.
tick_dep_clear(TICK_DEP_BIT_RCU);
return 0;
@@ -4050,7 +4008,7 @@
*/
init_completion(&rcu_state.barrier_completion);
atomic_set(&rcu_state.barrier_cpu_count, 2);
- get_online_cpus();
+ cpus_read_lock();
/*
* Force each CPU with callbacks to register a new callback.
@@ -4081,7 +4039,7 @@
rcu_state.barrier_sequence);
}
}
- put_online_cpus();
+ cpus_read_unlock();
/*
* Now that we have an rcu_barrier_callback() callback on each
@@ -4784,4 +4742,5 @@
#include "tree_stall.h"
#include "tree_exp.h"
+#include "tree_nocb.h"
#include "tree_plugin.h"
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
new file mode 100644
index 0000000..8fdf44f
--- /dev/null
+++ b/kernel/rcu/tree_nocb.h
@@ -0,0 +1,1496 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Read-Copy Update mechanism for mutual exclusion (tree-based version)
+ * Internal non-public definitions that provide either classic
+ * or preemptible semantics.
+ *
+ * Copyright Red Hat, 2009
+ * Copyright IBM Corporation, 2009
+ * Copyright SUSE, 2021
+ *
+ * Author: Ingo Molnar <mingo@elte.hu>
+ * Paul E. McKenney <paulmck@linux.ibm.com>
+ * Frederic Weisbecker <frederic@kernel.org>
+ */
+
+#ifdef CONFIG_RCU_NOCB_CPU
+static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
+static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
+static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
+{
+ return lockdep_is_held(&rdp->nocb_lock);
+}
+
+static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
+{
+ /* Race on early boot between thread creation and assignment */
+ if (!rdp->nocb_cb_kthread || !rdp->nocb_gp_kthread)
+ return true;
+
+ if (current == rdp->nocb_cb_kthread || current == rdp->nocb_gp_kthread)
+ if (in_task())
+ return true;
+ return false;
+}
+
+/*
+ * Offload callback processing from the boot-time-specified set of CPUs
+ * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads
+ * created that pull the callbacks from the corresponding CPU, wait for
+ * a grace period to elapse, and invoke the callbacks. These kthreads
+ * are organized into GP kthreads, which manage incoming callbacks, wait for
+ * grace periods, and awaken CB kthreads, and the CB kthreads, which only
+ * invoke callbacks. Each GP kthread invokes its own CBs. The no-CBs CPUs
+ * do a wake_up() on their GP kthread when they insert a callback into any
+ * empty list, unless the rcu_nocb_poll boot parameter has been specified,
+ * in which case each kthread actively polls its CPU. (Which isn't so great
+ * for energy efficiency, but which does reduce RCU's overhead on that CPU.)
+ *
+ * This is intended to be used in conjunction with Frederic Weisbecker's
+ * adaptive-idle work, which would seriously reduce OS jitter on CPUs
+ * running CPU-bound user-mode computations.
+ *
+ * Offloading of callbacks can also be used as an energy-efficiency
+ * measure because CPUs with no RCU callbacks queued are more aggressive
+ * about entering dyntick-idle mode.
+ */
+
+
+/*
+ * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
+ * If the list is invalid, a warning is emitted and all CPUs are offloaded.
+ */
+static int __init rcu_nocb_setup(char *str)
+{
+ alloc_bootmem_cpumask_var(&rcu_nocb_mask);
+ if (cpulist_parse(str, rcu_nocb_mask)) {
+ pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
+ cpumask_setall(rcu_nocb_mask);
+ }
+ return 1;
+}
+__setup("rcu_nocbs=", rcu_nocb_setup);
+
+static int __init parse_rcu_nocb_poll(char *arg)
+{
+ rcu_nocb_poll = true;
+ return 0;
+}
+early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
+
+/*
+ * Don't bother bypassing ->cblist if the call_rcu() rate is low.
+ * After all, the main point of bypassing is to avoid lock contention
+ * on ->nocb_lock, which only can happen at high call_rcu() rates.
+ */
+static int nocb_nobypass_lim_per_jiffy = 16 * 1000 / HZ;
+module_param(nocb_nobypass_lim_per_jiffy, int, 0);
+
+/*
+ * Acquire the specified rcu_data structure's ->nocb_bypass_lock. If the
+ * lock isn't immediately available, increment ->nocb_lock_contended to
+ * flag the contention.
+ */
+static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
+ __acquires(&rdp->nocb_bypass_lock)
+{
+ lockdep_assert_irqs_disabled();
+ if (raw_spin_trylock(&rdp->nocb_bypass_lock))
+ return;
+ atomic_inc(&rdp->nocb_lock_contended);
+ WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
+ smp_mb__after_atomic(); /* atomic_inc() before lock. */
+ raw_spin_lock(&rdp->nocb_bypass_lock);
+ smp_mb__before_atomic(); /* atomic_dec() after lock. */
+ atomic_dec(&rdp->nocb_lock_contended);
+}
+
+/*
+ * Spinwait until the specified rcu_data structure's ->nocb_lock is
+ * not contended. Please note that this is extremely special-purpose,
+ * relying on the fact that at most two kthreads and one CPU contend for
+ * this lock, and also that the two kthreads are guaranteed to have frequent
+ * grace-period-duration time intervals between successive acquisitions
+ * of the lock. This allows us to use an extremely simple throttling
+ * mechanism, and further to apply it only to the CPU doing floods of
+ * call_rcu() invocations. Don't try this at home!
+ */
+static void rcu_nocb_wait_contended(struct rcu_data *rdp)
+{
+ WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
+ while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)))
+ cpu_relax();
+}
+
+/*
+ * Conditionally acquire the specified rcu_data structure's
+ * ->nocb_bypass_lock.
+ */
+static bool rcu_nocb_bypass_trylock(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+ return raw_spin_trylock(&rdp->nocb_bypass_lock);
+}
+
+/*
+ * Release the specified rcu_data structure's ->nocb_bypass_lock.
+ */
+static void rcu_nocb_bypass_unlock(struct rcu_data *rdp)
+ __releases(&rdp->nocb_bypass_lock)
+{
+ lockdep_assert_irqs_disabled();
+ raw_spin_unlock(&rdp->nocb_bypass_lock);
+}
+
+/*
+ * Acquire the specified rcu_data structure's ->nocb_lock, but only
+ * if it corresponds to a no-CBs CPU.
+ */
+static void rcu_nocb_lock(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+ if (!rcu_rdp_is_offloaded(rdp))
+ return;
+ raw_spin_lock(&rdp->nocb_lock);
+}
+
+/*
+ * Release the specified rcu_data structure's ->nocb_lock, but only
+ * if it corresponds to a no-CBs CPU.
+ */
+static void rcu_nocb_unlock(struct rcu_data *rdp)
+{
+ if (rcu_rdp_is_offloaded(rdp)) {
+ lockdep_assert_irqs_disabled();
+ raw_spin_unlock(&rdp->nocb_lock);
+ }
+}
+
+/*
+ * Release the specified rcu_data structure's ->nocb_lock and restore
+ * interrupts, but only if it corresponds to a no-CBs CPU.
+ */
+static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
+ unsigned long flags)
+{
+ if (rcu_rdp_is_offloaded(rdp)) {
+ lockdep_assert_irqs_disabled();
+ raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
+ } else {
+ local_irq_restore(flags);
+ }
+}
+
+/* Lockdep check that ->cblist may be safely accessed. */
+static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+ if (rcu_rdp_is_offloaded(rdp))
+ lockdep_assert_held(&rdp->nocb_lock);
+}
+
+/*
+ * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
+ * grace period.
+ */
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
+{
+ swake_up_all(sq);
+}
+
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
+{
+ return &rnp->nocb_gp_wq[rcu_seq_ctr(rnp->gp_seq) & 0x1];
+}
+
+static void rcu_init_one_nocb(struct rcu_node *rnp)
+{
+ init_swait_queue_head(&rnp->nocb_gp_wq[0]);
+ init_swait_queue_head(&rnp->nocb_gp_wq[1]);
+}
+
+/* Is the specified CPU a no-CBs CPU? */
+bool rcu_is_nocb_cpu(int cpu)
+{
+ if (cpumask_available(rcu_nocb_mask))
+ return cpumask_test_cpu(cpu, rcu_nocb_mask);
+ return false;
+}
+
+static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
+ struct rcu_data *rdp,
+ bool force, unsigned long flags)
+ __releases(rdp_gp->nocb_gp_lock)
+{
+ bool needwake = false;
+
+ if (!READ_ONCE(rdp_gp->nocb_gp_kthread)) {
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("AlreadyAwake"));
+ return false;
+ }
+
+ if (rdp_gp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+ del_timer(&rdp_gp->nocb_timer);
+ }
+
+ if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
+ WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
+ needwake = true;
+ }
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+ if (needwake) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
+ wake_up_process(rdp_gp->nocb_gp_kthread);
+ }
+
+ return needwake;
+}
+
+/*
+ * Kick the GP kthread for this NOCB group.
+ */
+static bool wake_nocb_gp(struct rcu_data *rdp, bool force)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ return __wake_nocb_gp(rdp_gp, rdp, force, flags);
+}
+
+/*
+ * Arrange to wake the GP kthread for this NOCB group at some future
+ * time when it is safe to do so.
+ */
+static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
+ const char *reason)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+
+ /*
+ * Bypass wakeup overrides previous deferments. In case
+ * of callback storm, no need to wake up too early.
+ */
+ if (waketype == RCU_NOCB_WAKE_BYPASS) {
+ mod_timer(&rdp_gp->nocb_timer, jiffies + 2);
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
+ } else {
+ if (rdp_gp->nocb_defer_wakeup < RCU_NOCB_WAKE)
+ mod_timer(&rdp_gp->nocb_timer, jiffies + 1);
+ if (rdp_gp->nocb_defer_wakeup < waketype)
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
+ }
+
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason);
+}
+
+/*
+ * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
+ * However, if there is a callback to be enqueued and if ->nocb_bypass
+ * proves to be initially empty, just return false because the no-CB GP
+ * kthread may need to be awakened in this case.
+ *
+ * Note that this function always returns true if rhp is NULL.
+ */
+static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ unsigned long j)
+{
+ struct rcu_cblist rcl;
+
+ WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp));
+ rcu_lockdep_assert_cblist_protected(rdp);
+ lockdep_assert_held(&rdp->nocb_bypass_lock);
+ if (rhp && !rcu_cblist_n_cbs(&rdp->nocb_bypass)) {
+ raw_spin_unlock(&rdp->nocb_bypass_lock);
+ return false;
+ }
+ /* Note: ->cblist.len already accounts for ->nocb_bypass contents. */
+ if (rhp)
+ rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
+ rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
+ rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
+ WRITE_ONCE(rdp->nocb_bypass_first, j);
+ rcu_nocb_bypass_unlock(rdp);
+ return true;
+}
+
+/*
+ * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
+ * However, if there is a callback to be enqueued and if ->nocb_bypass
+ * proves to be initially empty, just return false because the no-CB GP
+ * kthread may need to be awakened in this case.
+ *
+ * Note that this function always returns true if rhp is NULL.
+ */
+static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ unsigned long j)
+{
+ if (!rcu_rdp_is_offloaded(rdp))
+ return true;
+ rcu_lockdep_assert_cblist_protected(rdp);
+ rcu_nocb_bypass_lock(rdp);
+ return rcu_nocb_do_flush_bypass(rdp, rhp, j);
+}
+
+/*
+ * If the ->nocb_bypass_lock is immediately available, flush the
+ * ->nocb_bypass queue into ->cblist.
+ */
+static void rcu_nocb_try_flush_bypass(struct rcu_data *rdp, unsigned long j)
+{
+ rcu_lockdep_assert_cblist_protected(rdp);
+ if (!rcu_rdp_is_offloaded(rdp) ||
+ !rcu_nocb_bypass_trylock(rdp))
+ return;
+ WARN_ON_ONCE(!rcu_nocb_do_flush_bypass(rdp, NULL, j));
+}
+
+/*
+ * See whether it is appropriate to use the ->nocb_bypass list in order
+ * to control contention on ->nocb_lock. A limited number of direct
+ * enqueues are permitted into ->cblist per jiffy. If ->nocb_bypass
+ * is non-empty, further callbacks must be placed into ->nocb_bypass,
+ * otherwise rcu_barrier() breaks. Use rcu_nocb_flush_bypass() to switch
+ * back to direct use of ->cblist. However, ->nocb_bypass should not be
+ * used if ->cblist is empty, because otherwise callbacks can be stranded
+ * on ->nocb_bypass because we cannot count on the current CPU ever again
+ * invoking call_rcu(). The general rule is that if ->nocb_bypass is
+ * non-empty, the corresponding no-CBs grace-period kthread must not be
+ * in an indefinite sleep state.
+ *
+ * Finally, it is not permitted to use the bypass during early boot,
+ * as doing so would confuse the auto-initialization code. Besides
+ * which, there is no point in worrying about lock contention while
+ * there is only one CPU in operation.
+ */
+static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ bool *was_alldone, unsigned long flags)
+{
+ unsigned long c;
+ unsigned long cur_gp_seq;
+ unsigned long j = jiffies;
+ long ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+
+ lockdep_assert_irqs_disabled();
+
+ // Pure softirq/rcuc based processing: no bypassing, no
+ // locking.
+ if (!rcu_rdp_is_offloaded(rdp)) {
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ return false;
+ }
+
+ // In the process of (de-)offloading: no bypassing, but
+ // locking.
+ if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
+ rcu_nocb_lock(rdp);
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ return false; /* Not offloaded, no bypassing. */
+ }
+
+ // Don't use ->nocb_bypass during early boot.
+ if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) {
+ rcu_nocb_lock(rdp);
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ return false;
+ }
+
+ // If we have advanced to a new jiffy, reset counts to allow
+ // moving back from ->nocb_bypass to ->cblist.
+ if (j == rdp->nocb_nobypass_last) {
+ c = rdp->nocb_nobypass_count + 1;
+ } else {
+ WRITE_ONCE(rdp->nocb_nobypass_last, j);
+ c = rdp->nocb_nobypass_count - nocb_nobypass_lim_per_jiffy;
+ if (ULONG_CMP_LT(rdp->nocb_nobypass_count,
+ nocb_nobypass_lim_per_jiffy))
+ c = 0;
+ else if (c > nocb_nobypass_lim_per_jiffy)
+ c = nocb_nobypass_lim_per_jiffy;
+ }
+ WRITE_ONCE(rdp->nocb_nobypass_count, c);
+
+ // If there hasn't yet been all that many ->cblist enqueues
+ // this jiffy, tell the caller to enqueue onto ->cblist. But flush
+ // ->nocb_bypass first.
+ if (rdp->nocb_nobypass_count < nocb_nobypass_lim_per_jiffy) {
+ rcu_nocb_lock(rdp);
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ if (*was_alldone)
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstQ"));
+ WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, j));
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+ return false; // Caller must enqueue the callback.
+ }
+
+ // If ->nocb_bypass has been used too long or is too full,
+ // flush ->nocb_bypass to ->cblist.
+ if ((ncbs && j != READ_ONCE(rdp->nocb_bypass_first)) ||
+ ncbs >= qhimark) {
+ rcu_nocb_lock(rdp);
+ if (!rcu_nocb_flush_bypass(rdp, rhp, j)) {
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ if (*was_alldone)
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstQ"));
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+ return false; // Caller must enqueue the callback.
+ }
+ if (j != rdp->nocb_gp_adv_time &&
+ rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
+ rcu_advance_cbs_nowake(rdp->mynode, rdp);
+ rdp->nocb_gp_adv_time = j;
+ }
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ return true; // Callback already enqueued.
+ }
+
+ // We need to use the bypass.
+ rcu_nocb_wait_contended(rdp);
+ rcu_nocb_bypass_lock(rdp);
+ ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+ rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
+ rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
+ if (!ncbs) {
+ WRITE_ONCE(rdp->nocb_bypass_first, j);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("FirstBQ"));
+ }
+ rcu_nocb_bypass_unlock(rdp);
+ smp_mb(); /* Order enqueue before wake. */
+ if (ncbs) {
+ local_irq_restore(flags);
+ } else {
+ // No-CBs GP kthread might be indefinitely asleep, if so, wake.
+ rcu_nocb_lock(rdp); // Rare during call_rcu() flood.
+ if (!rcu_segcblist_pend_cbs(&rdp->cblist)) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstBQwake"));
+ __call_rcu_nocb_wake(rdp, true, flags);
+ } else {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstBQnoWake"));
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ }
+ }
+ return true; // Callback already enqueued.
+}
+
+/*
+ * Awaken the no-CBs grace-period kthread if needed, either due to it
+ * legitimately being asleep or due to overload conditions.
+ *
+ * If warranted, also wake up the kthread servicing this CPUs queues.
+ */
+static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
+ unsigned long flags)
+ __releases(rdp->nocb_lock)
+{
+ unsigned long cur_gp_seq;
+ unsigned long j;
+ long len;
+ struct task_struct *t;
+
+ // If we are being polled or there is no kthread, just leave.
+ t = READ_ONCE(rdp->nocb_gp_kthread);
+ if (rcu_nocb_poll || !t) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("WakeNotPoll"));
+ return;
+ }
+ // Need to actually to a wakeup.
+ len = rcu_segcblist_n_cbs(&rdp->cblist);
+ if (was_alldone) {
+ rdp->qlen_last_fqs_check = len;
+ if (!irqs_disabled_flags(flags)) {
+ /* ... if queue was empty ... */
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp(rdp, false);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("WakeEmpty"));
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
+ TPS("WakeEmptyIsDeferred"));
+ }
+ } else if (len > rdp->qlen_last_fqs_check + qhimark) {
+ /* ... or if many callbacks queued. */
+ rdp->qlen_last_fqs_check = len;
+ j = jiffies;
+ if (j != rdp->nocb_gp_adv_time &&
+ rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
+ rcu_advance_cbs_nowake(rdp->mynode, rdp);
+ rdp->nocb_gp_adv_time = j;
+ }
+ smp_mb(); /* Enqueue before timer_pending(). */
+ if ((rdp->nocb_cb_sleep ||
+ !rcu_segcblist_ready_cbs(&rdp->cblist)) &&
+ !timer_pending(&rdp->nocb_timer)) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE,
+ TPS("WakeOvfIsDeferred"));
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
+ }
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
+ }
+ return;
+}
+
+/*
+ * Check if we ignore this rdp.
+ *
+ * We check that without holding the nocb lock but
+ * we make sure not to miss a freshly offloaded rdp
+ * with the current ordering:
+ *
+ * rdp_offload_toggle() nocb_gp_enabled_cb()
+ * ------------------------- ----------------------------
+ * WRITE flags LOCK nocb_gp_lock
+ * LOCK nocb_gp_lock READ/WRITE nocb_gp_sleep
+ * READ/WRITE nocb_gp_sleep UNLOCK nocb_gp_lock
+ * UNLOCK nocb_gp_lock READ flags
+ */
+static inline bool nocb_gp_enabled_cb(struct rcu_data *rdp)
+{
+ u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_GP;
+
+ return rcu_segcblist_test_flags(&rdp->cblist, flags);
+}
+
+static inline bool nocb_gp_update_state_deoffloading(struct rcu_data *rdp,
+ bool *needwake_state)
+{
+ struct rcu_segcblist *cblist = &rdp->cblist;
+
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) {
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) {
+ rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_GP);
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
+ *needwake_state = true;
+ }
+ return false;
+ }
+
+ /*
+ * De-offloading. Clear our flag and notify the de-offload worker.
+ * We will ignore this rdp until it ever gets re-offloaded.
+ */
+ WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP));
+ rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_GP);
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
+ *needwake_state = true;
+ return true;
+}
+
+
+/*
+ * No-CBs GP kthreads come here to wait for additional callbacks to show up
+ * or for grace periods to end.
+ */
+static void nocb_gp_wait(struct rcu_data *my_rdp)
+{
+ bool bypass = false;
+ long bypass_ncbs;
+ int __maybe_unused cpu = my_rdp->cpu;
+ unsigned long cur_gp_seq;
+ unsigned long flags;
+ bool gotcbs = false;
+ unsigned long j = jiffies;
+ bool needwait_gp = false; // This prevents actual uninitialized use.
+ bool needwake;
+ bool needwake_gp;
+ struct rcu_data *rdp;
+ struct rcu_node *rnp;
+ unsigned long wait_gp_seq = 0; // Suppress "use uninitialized" warning.
+ bool wasempty = false;
+
+ /*
+ * Each pass through the following loop checks for CBs and for the
+ * nearest grace period (if any) to wait for next. The CB kthreads
+ * and the global grace-period kthread are awakened if needed.
+ */
+ WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp);
+ for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) {
+ bool needwake_state = false;
+
+ if (!nocb_gp_enabled_cb(rdp))
+ continue;
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
+ rcu_nocb_lock_irqsave(rdp, flags);
+ if (nocb_gp_update_state_deoffloading(rdp, &needwake_state)) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ if (needwake_state)
+ swake_up_one(&rdp->nocb_state_wq);
+ continue;
+ }
+ bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+ if (bypass_ncbs &&
+ (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) ||
+ bypass_ncbs > 2 * qhimark)) {
+ // Bypass full or old, so flush it.
+ (void)rcu_nocb_try_flush_bypass(rdp, j);
+ bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+ } else if (!bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ if (needwake_state)
+ swake_up_one(&rdp->nocb_state_wq);
+ continue; /* No callbacks here, try next. */
+ }
+ if (bypass_ncbs) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("Bypass"));
+ bypass = true;
+ }
+ rnp = rdp->mynode;
+
+ // Advance callbacks if helpful and low contention.
+ needwake_gp = false;
+ if (!rcu_segcblist_restempty(&rdp->cblist,
+ RCU_NEXT_READY_TAIL) ||
+ (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rnp->gp_seq, cur_gp_seq))) {
+ raw_spin_lock_rcu_node(rnp); /* irqs disabled. */
+ needwake_gp = rcu_advance_cbs(rnp, rdp);
+ wasempty = rcu_segcblist_restempty(&rdp->cblist,
+ RCU_NEXT_READY_TAIL);
+ raw_spin_unlock_rcu_node(rnp); /* irqs disabled. */
+ }
+ // Need to wait on some grace period?
+ WARN_ON_ONCE(wasempty &&
+ !rcu_segcblist_restempty(&rdp->cblist,
+ RCU_NEXT_READY_TAIL));
+ if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq)) {
+ if (!needwait_gp ||
+ ULONG_CMP_LT(cur_gp_seq, wait_gp_seq))
+ wait_gp_seq = cur_gp_seq;
+ needwait_gp = true;
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("NeedWaitGP"));
+ }
+ if (rcu_segcblist_ready_cbs(&rdp->cblist)) {
+ needwake = rdp->nocb_cb_sleep;
+ WRITE_ONCE(rdp->nocb_cb_sleep, false);
+ smp_mb(); /* CB invocation -after- GP end. */
+ } else {
+ needwake = false;
+ }
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ if (needwake) {
+ swake_up_one(&rdp->nocb_cb_wq);
+ gotcbs = true;
+ }
+ if (needwake_gp)
+ rcu_gp_kthread_wake();
+ if (needwake_state)
+ swake_up_one(&rdp->nocb_state_wq);
+ }
+
+ my_rdp->nocb_gp_bypass = bypass;
+ my_rdp->nocb_gp_gp = needwait_gp;
+ my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
+
+ if (bypass && !rcu_nocb_poll) {
+ // At least one child with non-empty ->nocb_bypass, so set
+ // timer in order to avoid stranding its callbacks.
+ wake_nocb_gp_defer(my_rdp, RCU_NOCB_WAKE_BYPASS,
+ TPS("WakeBypassIsDeferred"));
+ }
+ if (rcu_nocb_poll) {
+ /* Polling, so trace if first poll in the series. */
+ if (gotcbs)
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll"));
+ schedule_timeout_idle(1);
+ } else if (!needwait_gp) {
+ /* Wait for callbacks to appear. */
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Sleep"));
+ swait_event_interruptible_exclusive(my_rdp->nocb_gp_wq,
+ !READ_ONCE(my_rdp->nocb_gp_sleep));
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("EndSleep"));
+ } else {
+ rnp = my_rdp->mynode;
+ trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("StartWait"));
+ swait_event_interruptible_exclusive(
+ rnp->nocb_gp_wq[rcu_seq_ctr(wait_gp_seq) & 0x1],
+ rcu_seq_done(&rnp->gp_seq, wait_gp_seq) ||
+ !READ_ONCE(my_rdp->nocb_gp_sleep));
+ trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("EndWait"));
+ }
+ if (!rcu_nocb_poll) {
+ raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
+ if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+ del_timer(&my_rdp->nocb_timer);
+ }
+ WRITE_ONCE(my_rdp->nocb_gp_sleep, true);
+ raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
+ }
+ my_rdp->nocb_gp_seq = -1;
+ WARN_ON(signal_pending(current));
+}
+
+/*
+ * No-CBs grace-period-wait kthread. There is one of these per group
+ * of CPUs, but only once at least one CPU in that group has come online
+ * at least once since boot. This kthread checks for newly posted
+ * callbacks from any of the CPUs it is responsible for, waits for a
+ * grace period, then awakens all of the rcu_nocb_cb_kthread() instances
+ * that then have callback-invocation work to do.
+ */
+static int rcu_nocb_gp_kthread(void *arg)
+{
+ struct rcu_data *rdp = arg;
+
+ for (;;) {
+ WRITE_ONCE(rdp->nocb_gp_loops, rdp->nocb_gp_loops + 1);
+ nocb_gp_wait(rdp);
+ cond_resched_tasks_rcu_qs();
+ }
+ return 0;
+}
+
+static inline bool nocb_cb_can_run(struct rcu_data *rdp)
+{
+ u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_CB;
+ return rcu_segcblist_test_flags(&rdp->cblist, flags);
+}
+
+static inline bool nocb_cb_wait_cond(struct rcu_data *rdp)
+{
+ return nocb_cb_can_run(rdp) && !READ_ONCE(rdp->nocb_cb_sleep);
+}
+
+/*
+ * Invoke any ready callbacks from the corresponding no-CBs CPU,
+ * then, if there are no more, wait for more to appear.
+ */
+static void nocb_cb_wait(struct rcu_data *rdp)
+{
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long cur_gp_seq;
+ unsigned long flags;
+ bool needwake_state = false;
+ bool needwake_gp = false;
+ bool can_sleep = true;
+ struct rcu_node *rnp = rdp->mynode;
+
+ local_irq_save(flags);
+ rcu_momentary_dyntick_idle();
+ local_irq_restore(flags);
+ /*
+ * Disable BH to provide the expected environment. Also, when
+ * transitioning to/from NOCB mode, a self-requeuing callback might
+ * be invoked from softirq. A short grace period could cause both
+ * instances of this callback would execute concurrently.
+ */
+ local_bh_disable();
+ rcu_do_batch(rdp);
+ local_bh_enable();
+ lockdep_assert_irqs_enabled();
+ rcu_nocb_lock_irqsave(rdp, flags);
+ if (rcu_segcblist_nextgp(cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rnp->gp_seq, cur_gp_seq) &&
+ raw_spin_trylock_rcu_node(rnp)) { /* irqs already disabled. */
+ needwake_gp = rcu_advance_cbs(rdp->mynode, rdp);
+ raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
+ }
+
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) {
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)) {
+ rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_CB);
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP))
+ needwake_state = true;
+ }
+ if (rcu_segcblist_ready_cbs(cblist))
+ can_sleep = false;
+ } else {
+ /*
+ * De-offloading. Clear our flag and notify the de-offload worker.
+ * We won't touch the callbacks and keep sleeping until we ever
+ * get re-offloaded.
+ */
+ WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB));
+ rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_CB);
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP))
+ needwake_state = true;
+ }
+
+ WRITE_ONCE(rdp->nocb_cb_sleep, can_sleep);
+
+ if (rdp->nocb_cb_sleep)
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep"));
+
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ if (needwake_gp)
+ rcu_gp_kthread_wake();
+
+ if (needwake_state)
+ swake_up_one(&rdp->nocb_state_wq);
+
+ do {
+ swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
+ nocb_cb_wait_cond(rdp));
+
+ // VVV Ensure CB invocation follows _sleep test.
+ if (smp_load_acquire(&rdp->nocb_cb_sleep)) { // ^^^
+ WARN_ON(signal_pending(current));
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
+ }
+ } while (!nocb_cb_can_run(rdp));
+}
+
+/*
+ * Per-rcu_data kthread, but only for no-CBs CPUs. Repeatedly invoke
+ * nocb_cb_wait() to do the dirty work.
+ */
+static int rcu_nocb_cb_kthread(void *arg)
+{
+ struct rcu_data *rdp = arg;
+
+ // Each pass through this loop does one callback batch, and,
+ // if there are no more ready callbacks, waits for them.
+ for (;;) {
+ nocb_cb_wait(rdp);
+ cond_resched_tasks_rcu_qs();
+ }
+ return 0;
+}
+
+/* Is a deferred wakeup of rcu_nocb_kthread() required? */
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
+{
+ return READ_ONCE(rdp->nocb_defer_wakeup) >= level;
+}
+
+/* Do a deferred wakeup of rcu_nocb_kthread(). */
+static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp_gp,
+ struct rcu_data *rdp, int level,
+ unsigned long flags)
+ __releases(rdp_gp->nocb_gp_lock)
+{
+ int ndw;
+ int ret;
+
+ if (!rcu_nocb_need_deferred_wakeup(rdp_gp, level)) {
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+ return false;
+ }
+
+ ndw = rdp_gp->nocb_defer_wakeup;
+ ret = __wake_nocb_gp(rdp_gp, rdp, ndw == RCU_NOCB_WAKE_FORCE, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake"));
+
+ return ret;
+}
+
+/* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */
+static void do_nocb_deferred_wakeup_timer(struct timer_list *t)
+{
+ unsigned long flags;
+ struct rcu_data *rdp = from_timer(rdp, t, nocb_timer);
+
+ WARN_ON_ONCE(rdp->nocb_gp_rdp != rdp);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Timer"));
+
+ raw_spin_lock_irqsave(&rdp->nocb_gp_lock, flags);
+ smp_mb__after_spinlock(); /* Timer expire before wakeup. */
+ do_nocb_deferred_wakeup_common(rdp, rdp, RCU_NOCB_WAKE_BYPASS, flags);
+}
+
+/*
+ * Do a deferred wakeup of rcu_nocb_kthread() from fastpath.
+ * This means we do an inexact common-case check. Note that if
+ * we miss, ->nocb_timer will eventually clean things up.
+ */
+static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ if (!rdp_gp || !rcu_nocb_need_deferred_wakeup(rdp_gp, RCU_NOCB_WAKE))
+ return false;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ return do_nocb_deferred_wakeup_common(rdp_gp, rdp, RCU_NOCB_WAKE, flags);
+}
+
+void rcu_nocb_flush_deferred_wakeup(void)
+{
+ do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data));
+}
+EXPORT_SYMBOL_GPL(rcu_nocb_flush_deferred_wakeup);
+
+static int rdp_offload_toggle(struct rcu_data *rdp,
+ bool offload, unsigned long flags)
+ __releases(rdp->nocb_lock)
+{
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+ bool wake_gp = false;
+
+ rcu_segcblist_offload(cblist, offload);
+
+ if (rdp->nocb_cb_sleep)
+ rdp->nocb_cb_sleep = false;
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+
+ /*
+ * Ignore former value of nocb_cb_sleep and force wake up as it could
+ * have been spuriously set to false already.
+ */
+ swake_up_one(&rdp->nocb_cb_wq);
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ if (rdp_gp->nocb_gp_sleep) {
+ rdp_gp->nocb_gp_sleep = false;
+ wake_gp = true;
+ }
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+
+ if (wake_gp)
+ wake_up_process(rdp_gp->nocb_gp_kthread);
+
+ return 0;
+}
+
+static long rcu_nocb_rdp_deoffload(void *arg)
+{
+ struct rcu_data *rdp = arg;
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long flags;
+ int ret;
+
+ WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
+
+ pr_info("De-offloading %d\n", rdp->cpu);
+
+ rcu_nocb_lock_irqsave(rdp, flags);
+ /*
+ * Flush once and for all now. This suffices because we are
+ * running on the target CPU holding ->nocb_lock (thus having
+ * interrupts disabled), and because rdp_offload_toggle()
+ * invokes rcu_segcblist_offload(), which clears SEGCBLIST_OFFLOADED.
+ * Thus future calls to rcu_segcblist_completely_offloaded() will
+ * return false, which means that future calls to rcu_nocb_try_bypass()
+ * will refuse to put anything into the bypass.
+ */
+ WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies));
+ ret = rdp_offload_toggle(rdp, false, flags);
+ swait_event_exclusive(rdp->nocb_state_wq,
+ !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
+ SEGCBLIST_KTHREAD_GP));
+ /*
+ * Lock one last time to acquire latest callback updates from kthreads
+ * so we can later handle callbacks locally without locking.
+ */
+ rcu_nocb_lock_irqsave(rdp, flags);
+ /*
+ * Theoretically we could set SEGCBLIST_SOFTIRQ_ONLY after the nocb
+ * lock is released but how about being paranoid for once?
+ */
+ rcu_segcblist_set_flags(cblist, SEGCBLIST_SOFTIRQ_ONLY);
+ /*
+ * With SEGCBLIST_SOFTIRQ_ONLY, we can't use
+ * rcu_nocb_unlock_irqrestore() anymore.
+ */
+ raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
+
+ /* Sanity check */
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+
+
+ return ret;
+}
+
+int rcu_nocb_cpu_deoffload(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ int ret = 0;
+
+ mutex_lock(&rcu_state.barrier_mutex);
+ cpus_read_lock();
+ if (rcu_rdp_is_offloaded(rdp)) {
+ if (cpu_online(cpu)) {
+ ret = work_on_cpu(cpu, rcu_nocb_rdp_deoffload, rdp);
+ if (!ret)
+ cpumask_clear_cpu(cpu, rcu_nocb_mask);
+ } else {
+ pr_info("NOCB: Can't CB-deoffload an offline CPU\n");
+ ret = -EINVAL;
+ }
+ }
+ cpus_read_unlock();
+ mutex_unlock(&rcu_state.barrier_mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rcu_nocb_cpu_deoffload);
+
+static long rcu_nocb_rdp_offload(void *arg)
+{
+ struct rcu_data *rdp = arg;
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long flags;
+ int ret;
+
+ WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
+ /*
+ * For now we only support re-offload, ie: the rdp must have been
+ * offloaded on boot first.
+ */
+ if (!rdp->nocb_gp_rdp)
+ return -EINVAL;
+
+ pr_info("Offloading %d\n", rdp->cpu);
+ /*
+ * Can't use rcu_nocb_lock_irqsave() while we are in
+ * SEGCBLIST_SOFTIRQ_ONLY mode.
+ */
+ raw_spin_lock_irqsave(&rdp->nocb_lock, flags);
+
+ /*
+ * We didn't take the nocb lock while working on the
+ * rdp->cblist in SEGCBLIST_SOFTIRQ_ONLY mode.
+ * Every modifications that have been done previously on
+ * rdp->cblist must be visible remotely by the nocb kthreads
+ * upon wake up after reading the cblist flags.
+ *
+ * The layout against nocb_lock enforces that ordering:
+ *
+ * __rcu_nocb_rdp_offload() nocb_cb_wait()/nocb_gp_wait()
+ * ------------------------- ----------------------------
+ * WRITE callbacks rcu_nocb_lock()
+ * rcu_nocb_lock() READ flags
+ * WRITE flags READ callbacks
+ * rcu_nocb_unlock() rcu_nocb_unlock()
+ */
+ ret = rdp_offload_toggle(rdp, true, flags);
+ swait_event_exclusive(rdp->nocb_state_wq,
+ rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) &&
+ rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP));
+
+ return ret;
+}
+
+int rcu_nocb_cpu_offload(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ int ret = 0;
+
+ mutex_lock(&rcu_state.barrier_mutex);
+ cpus_read_lock();
+ if (!rcu_rdp_is_offloaded(rdp)) {
+ if (cpu_online(cpu)) {
+ ret = work_on_cpu(cpu, rcu_nocb_rdp_offload, rdp);
+ if (!ret)
+ cpumask_set_cpu(cpu, rcu_nocb_mask);
+ } else {
+ pr_info("NOCB: Can't CB-offload an offline CPU\n");
+ ret = -EINVAL;
+ }
+ }
+ cpus_read_unlock();
+ mutex_unlock(&rcu_state.barrier_mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
+
+void __init rcu_init_nohz(void)
+{
+ int cpu;
+ bool need_rcu_nocb_mask = false;
+ struct rcu_data *rdp;
+
+#if defined(CONFIG_NO_HZ_FULL)
+ if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask))
+ need_rcu_nocb_mask = true;
+#endif /* #if defined(CONFIG_NO_HZ_FULL) */
+
+ if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
+ if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
+ pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
+ return;
+ }
+ }
+ if (!cpumask_available(rcu_nocb_mask))
+ return;
+
+#if defined(CONFIG_NO_HZ_FULL)
+ if (tick_nohz_full_running)
+ cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
+#endif /* #if defined(CONFIG_NO_HZ_FULL) */
+
+ if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
+ pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
+ cpumask_and(rcu_nocb_mask, cpu_possible_mask,
+ rcu_nocb_mask);
+ }
+ if (cpumask_empty(rcu_nocb_mask))
+ pr_info("\tOffload RCU callbacks from CPUs: (none).\n");
+ else
+ pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n",
+ cpumask_pr_args(rcu_nocb_mask));
+ if (rcu_nocb_poll)
+ pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
+
+ for_each_cpu(cpu, rcu_nocb_mask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (rcu_segcblist_empty(&rdp->cblist))
+ rcu_segcblist_init(&rdp->cblist);
+ rcu_segcblist_offload(&rdp->cblist, true);
+ rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB);
+ rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_GP);
+ }
+ rcu_organize_nocb_kthreads();
+}
+
+/* Initialize per-rcu_data variables for no-CBs CPUs. */
+static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
+{
+ init_swait_queue_head(&rdp->nocb_cb_wq);
+ init_swait_queue_head(&rdp->nocb_gp_wq);
+ init_swait_queue_head(&rdp->nocb_state_wq);
+ raw_spin_lock_init(&rdp->nocb_lock);
+ raw_spin_lock_init(&rdp->nocb_bypass_lock);
+ raw_spin_lock_init(&rdp->nocb_gp_lock);
+ timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0);
+ rcu_cblist_init(&rdp->nocb_bypass);
+}
+
+/*
+ * If the specified CPU is a no-CBs CPU that does not already have its
+ * rcuo CB kthread, spawn it. Additionally, if the rcuo GP kthread
+ * for this CPU's group has not yet been created, spawn it as well.
+ */
+static void rcu_spawn_one_nocb_kthread(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ struct rcu_data *rdp_gp;
+ struct task_struct *t;
+
+ /*
+ * If this isn't a no-CBs CPU or if it already has an rcuo kthread,
+ * then nothing to do.
+ */
+ if (!rcu_is_nocb_cpu(cpu) || rdp->nocb_cb_kthread)
+ return;
+
+ /* If we didn't spawn the GP kthread first, reorganize! */
+ rdp_gp = rdp->nocb_gp_rdp;
+ if (!rdp_gp->nocb_gp_kthread) {
+ t = kthread_run(rcu_nocb_gp_kthread, rdp_gp,
+ "rcuog/%d", rdp_gp->cpu);
+ if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo GP kthread, OOM is now expected behavior\n", __func__))
+ return;
+ WRITE_ONCE(rdp_gp->nocb_gp_kthread, t);
+ }
+
+ /* Spawn the kthread for this CPU. */
+ t = kthread_run(rcu_nocb_cb_kthread, rdp,
+ "rcuo%c/%d", rcu_state.abbr, cpu);
+ if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__))
+ return;
+ WRITE_ONCE(rdp->nocb_cb_kthread, t);
+ WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
+}
+
+/*
+ * If the specified CPU is a no-CBs CPU that does not already have its
+ * rcuo kthread, spawn it.
+ */
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
+{
+ if (rcu_scheduler_fully_active)
+ rcu_spawn_one_nocb_kthread(cpu);
+}
+
+/*
+ * Once the scheduler is running, spawn rcuo kthreads for all online
+ * no-CBs CPUs. This assumes that the early_initcall()s happen before
+ * non-boot CPUs come online -- if this changes, we will need to add
+ * some mutual exclusion.
+ */
+static void __init rcu_spawn_nocb_kthreads(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu)
+ rcu_spawn_cpu_nocb_kthread(cpu);
+}
+
+/* How many CB CPU IDs per GP kthread? Default of -1 for sqrt(nr_cpu_ids). */
+static int rcu_nocb_gp_stride = -1;
+module_param(rcu_nocb_gp_stride, int, 0444);
+
+/*
+ * Initialize GP-CB relationships for all no-CBs CPU.
+ */
+static void __init rcu_organize_nocb_kthreads(void)
+{
+ int cpu;
+ bool firsttime = true;
+ bool gotnocbs = false;
+ bool gotnocbscbs = true;
+ int ls = rcu_nocb_gp_stride;
+ int nl = 0; /* Next GP kthread. */
+ struct rcu_data *rdp;
+ struct rcu_data *rdp_gp = NULL; /* Suppress misguided gcc warn. */
+ struct rcu_data *rdp_prev = NULL;
+
+ if (!cpumask_available(rcu_nocb_mask))
+ return;
+ if (ls == -1) {
+ ls = nr_cpu_ids / int_sqrt(nr_cpu_ids);
+ rcu_nocb_gp_stride = ls;
+ }
+
+ /*
+ * Each pass through this loop sets up one rcu_data structure.
+ * Should the corresponding CPU come online in the future, then
+ * we will spawn the needed set of rcu_nocb_kthread() kthreads.
+ */
+ for_each_cpu(cpu, rcu_nocb_mask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (rdp->cpu >= nl) {
+ /* New GP kthread, set up for CBs & next GP. */
+ gotnocbs = true;
+ nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls;
+ rdp->nocb_gp_rdp = rdp;
+ rdp_gp = rdp;
+ if (dump_tree) {
+ if (!firsttime)
+ pr_cont("%s\n", gotnocbscbs
+ ? "" : " (self only)");
+ gotnocbscbs = false;
+ firsttime = false;
+ pr_alert("%s: No-CB GP kthread CPU %d:",
+ __func__, cpu);
+ }
+ } else {
+ /* Another CB kthread, link to previous GP kthread. */
+ gotnocbscbs = true;
+ rdp->nocb_gp_rdp = rdp_gp;
+ rdp_prev->nocb_next_cb_rdp = rdp;
+ if (dump_tree)
+ pr_cont(" %d", cpu);
+ }
+ rdp_prev = rdp;
+ }
+ if (gotnocbs && dump_tree)
+ pr_cont("%s\n", gotnocbscbs ? "" : " (self only)");
+}
+
+/*
+ * Bind the current task to the offloaded CPUs. If there are no offloaded
+ * CPUs, leave the task unbound. Splat if the bind attempt fails.
+ */
+void rcu_bind_current_to_nocb(void)
+{
+ if (cpumask_available(rcu_nocb_mask) && cpumask_weight(rcu_nocb_mask))
+ WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask));
+}
+EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb);
+
+// The ->on_cpu field is available only in CONFIG_SMP=y, so...
+#ifdef CONFIG_SMP
+static char *show_rcu_should_be_on_cpu(struct task_struct *tsp)
+{
+ return tsp && task_is_running(tsp) && !tsp->on_cpu ? "!" : "";
+}
+#else // #ifdef CONFIG_SMP
+static char *show_rcu_should_be_on_cpu(struct task_struct *tsp)
+{
+ return "";
+}
+#endif // #else #ifdef CONFIG_SMP
+
+/*
+ * Dump out nocb grace-period kthread state for the specified rcu_data
+ * structure.
+ */
+static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
+{
+ struct rcu_node *rnp = rdp->mynode;
+
+ pr_info("nocb GP %d %c%c%c%c%c %c[%c%c] %c%c:%ld rnp %d:%d %lu %c CPU %d%s\n",
+ rdp->cpu,
+ "kK"[!!rdp->nocb_gp_kthread],
+ "lL"[raw_spin_is_locked(&rdp->nocb_gp_lock)],
+ "dD"[!!rdp->nocb_defer_wakeup],
+ "tT"[timer_pending(&rdp->nocb_timer)],
+ "sS"[!!rdp->nocb_gp_sleep],
+ ".W"[swait_active(&rdp->nocb_gp_wq)],
+ ".W"[swait_active(&rnp->nocb_gp_wq[0])],
+ ".W"[swait_active(&rnp->nocb_gp_wq[1])],
+ ".B"[!!rdp->nocb_gp_bypass],
+ ".G"[!!rdp->nocb_gp_gp],
+ (long)rdp->nocb_gp_seq,
+ rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
+ rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
+ rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
+}
+
+/* Dump out nocb kthread state for the specified rcu_data structure. */
+static void show_rcu_nocb_state(struct rcu_data *rdp)
+{
+ char bufw[20];
+ char bufr[20];
+ struct rcu_segcblist *rsclp = &rdp->cblist;
+ bool waslocked;
+ bool wassleep;
+
+ if (rdp->nocb_gp_rdp == rdp)
+ show_rcu_nocb_gp_state(rdp);
+
+ sprintf(bufw, "%ld", rsclp->gp_seq[RCU_WAIT_TAIL]);
+ sprintf(bufr, "%ld", rsclp->gp_seq[RCU_NEXT_READY_TAIL]);
+ pr_info(" CB %d^%d->%d %c%c%c%c%c%c F%ld L%ld C%d %c%c%s%c%s%c%c q%ld %c CPU %d%s\n",
+ rdp->cpu, rdp->nocb_gp_rdp->cpu,
+ rdp->nocb_next_cb_rdp ? rdp->nocb_next_cb_rdp->cpu : -1,
+ "kK"[!!rdp->nocb_cb_kthread],
+ "bB"[raw_spin_is_locked(&rdp->nocb_bypass_lock)],
+ "cC"[!!atomic_read(&rdp->nocb_lock_contended)],
+ "lL"[raw_spin_is_locked(&rdp->nocb_lock)],
+ "sS"[!!rdp->nocb_cb_sleep],
+ ".W"[swait_active(&rdp->nocb_cb_wq)],
+ jiffies - rdp->nocb_bypass_first,
+ jiffies - rdp->nocb_nobypass_last,
+ rdp->nocb_nobypass_count,
+ ".D"[rcu_segcblist_ready_cbs(rsclp)],
+ ".W"[!rcu_segcblist_segempty(rsclp, RCU_WAIT_TAIL)],
+ rcu_segcblist_segempty(rsclp, RCU_WAIT_TAIL) ? "" : bufw,
+ ".R"[!rcu_segcblist_segempty(rsclp, RCU_NEXT_READY_TAIL)],
+ rcu_segcblist_segempty(rsclp, RCU_NEXT_READY_TAIL) ? "" : bufr,
+ ".N"[!rcu_segcblist_segempty(rsclp, RCU_NEXT_TAIL)],
+ ".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
+ rcu_segcblist_n_cbs(&rdp->cblist),
+ rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
+ rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
+
+ /* It is OK for GP kthreads to have GP state. */
+ if (rdp->nocb_gp_rdp == rdp)
+ return;
+
+ waslocked = raw_spin_is_locked(&rdp->nocb_gp_lock);
+ wassleep = swait_active(&rdp->nocb_gp_wq);
+ if (!rdp->nocb_gp_sleep && !waslocked && !wassleep)
+ return; /* Nothing untoward. */
+
+ pr_info(" nocb GP activity on CB-only CPU!!! %c%c%c %c\n",
+ "lL"[waslocked],
+ "dD"[!!rdp->nocb_defer_wakeup],
+ "sS"[!!rdp->nocb_gp_sleep],
+ ".W"[wassleep]);
+}
+
+#else /* #ifdef CONFIG_RCU_NOCB_CPU */
+
+static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
+{
+ return 0;
+}
+
+static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
+{
+ return false;
+}
+
+/* No ->nocb_lock to acquire. */
+static void rcu_nocb_lock(struct rcu_data *rdp)
+{
+}
+
+/* No ->nocb_lock to release. */
+static void rcu_nocb_unlock(struct rcu_data *rdp)
+{
+}
+
+/* No ->nocb_lock to release. */
+static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
+ unsigned long flags)
+{
+ local_irq_restore(flags);
+}
+
+/* Lockdep check that ->cblist may be safely accessed. */
+static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+}
+
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
+{
+}
+
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
+{
+ return NULL;
+}
+
+static void rcu_init_one_nocb(struct rcu_node *rnp)
+{
+}
+
+static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ unsigned long j)
+{
+ return true;
+}
+
+static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ bool *was_alldone, unsigned long flags)
+{
+ return false;
+}
+
+static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
+ unsigned long flags)
+{
+ WARN_ON_ONCE(1); /* Should be dead code! */
+}
+
+static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
+{
+}
+
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
+{
+ return false;
+}
+
+static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
+{
+ return false;
+}
+
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
+{
+}
+
+static void __init rcu_spawn_nocb_kthreads(void)
+{
+}
+
+static void show_rcu_nocb_state(struct rcu_data *rdp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index de1dc3b..7a4876a 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -13,39 +13,6 @@
#include "../locking/rtmutex_common.h"
-#ifdef CONFIG_RCU_NOCB_CPU
-static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
-static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
-static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
-{
- return lockdep_is_held(&rdp->nocb_lock);
-}
-
-static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
-{
- /* Race on early boot between thread creation and assignment */
- if (!rdp->nocb_cb_kthread || !rdp->nocb_gp_kthread)
- return true;
-
- if (current == rdp->nocb_cb_kthread || current == rdp->nocb_gp_kthread)
- if (in_task())
- return true;
- return false;
-}
-
-#else
-static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
-{
- return 0;
-}
-
-static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
-{
- return false;
-}
-
-#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
-
static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
{
/*
@@ -346,7 +313,7 @@
trace_rcu_utilization(TPS("Start context switch"));
lockdep_assert_irqs_disabled();
- WARN_ON_ONCE(!preempt && rcu_preempt_depth() > 0);
+ WARN_ONCE(!preempt && rcu_preempt_depth() > 0, "Voluntary context switch within RCU read-side critical section!");
if (rcu_preempt_depth() > 0 &&
!t->rcu_read_unlock_special.b.blocked) {
@@ -405,17 +372,20 @@
static void rcu_preempt_read_enter(void)
{
- current->rcu_read_lock_nesting++;
+ WRITE_ONCE(current->rcu_read_lock_nesting, READ_ONCE(current->rcu_read_lock_nesting) + 1);
}
static int rcu_preempt_read_exit(void)
{
- return --current->rcu_read_lock_nesting;
+ int ret = READ_ONCE(current->rcu_read_lock_nesting) - 1;
+
+ WRITE_ONCE(current->rcu_read_lock_nesting, ret);
+ return ret;
}
static void rcu_preempt_depth_set(int val)
{
- current->rcu_read_lock_nesting = val;
+ WRITE_ONCE(current->rcu_read_lock_nesting, val);
}
/*
@@ -1479,1460 +1449,6 @@
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
-#ifdef CONFIG_RCU_NOCB_CPU
-
-/*
- * Offload callback processing from the boot-time-specified set of CPUs
- * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads
- * created that pull the callbacks from the corresponding CPU, wait for
- * a grace period to elapse, and invoke the callbacks. These kthreads
- * are organized into GP kthreads, which manage incoming callbacks, wait for
- * grace periods, and awaken CB kthreads, and the CB kthreads, which only
- * invoke callbacks. Each GP kthread invokes its own CBs. The no-CBs CPUs
- * do a wake_up() on their GP kthread when they insert a callback into any
- * empty list, unless the rcu_nocb_poll boot parameter has been specified,
- * in which case each kthread actively polls its CPU. (Which isn't so great
- * for energy efficiency, but which does reduce RCU's overhead on that CPU.)
- *
- * This is intended to be used in conjunction with Frederic Weisbecker's
- * adaptive-idle work, which would seriously reduce OS jitter on CPUs
- * running CPU-bound user-mode computations.
- *
- * Offloading of callbacks can also be used as an energy-efficiency
- * measure because CPUs with no RCU callbacks queued are more aggressive
- * about entering dyntick-idle mode.
- */
-
-
-/*
- * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
- * If the list is invalid, a warning is emitted and all CPUs are offloaded.
- */
-static int __init rcu_nocb_setup(char *str)
-{
- alloc_bootmem_cpumask_var(&rcu_nocb_mask);
- if (cpulist_parse(str, rcu_nocb_mask)) {
- pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
- cpumask_setall(rcu_nocb_mask);
- }
- return 1;
-}
-__setup("rcu_nocbs=", rcu_nocb_setup);
-
-static int __init parse_rcu_nocb_poll(char *arg)
-{
- rcu_nocb_poll = true;
- return 0;
-}
-early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
-
-/*
- * Don't bother bypassing ->cblist if the call_rcu() rate is low.
- * After all, the main point of bypassing is to avoid lock contention
- * on ->nocb_lock, which only can happen at high call_rcu() rates.
- */
-static int nocb_nobypass_lim_per_jiffy = 16 * 1000 / HZ;
-module_param(nocb_nobypass_lim_per_jiffy, int, 0);
-
-/*
- * Acquire the specified rcu_data structure's ->nocb_bypass_lock. If the
- * lock isn't immediately available, increment ->nocb_lock_contended to
- * flag the contention.
- */
-static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
- __acquires(&rdp->nocb_bypass_lock)
-{
- lockdep_assert_irqs_disabled();
- if (raw_spin_trylock(&rdp->nocb_bypass_lock))
- return;
- atomic_inc(&rdp->nocb_lock_contended);
- WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
- smp_mb__after_atomic(); /* atomic_inc() before lock. */
- raw_spin_lock(&rdp->nocb_bypass_lock);
- smp_mb__before_atomic(); /* atomic_dec() after lock. */
- atomic_dec(&rdp->nocb_lock_contended);
-}
-
-/*
- * Spinwait until the specified rcu_data structure's ->nocb_lock is
- * not contended. Please note that this is extremely special-purpose,
- * relying on the fact that at most two kthreads and one CPU contend for
- * this lock, and also that the two kthreads are guaranteed to have frequent
- * grace-period-duration time intervals between successive acquisitions
- * of the lock. This allows us to use an extremely simple throttling
- * mechanism, and further to apply it only to the CPU doing floods of
- * call_rcu() invocations. Don't try this at home!
- */
-static void rcu_nocb_wait_contended(struct rcu_data *rdp)
-{
- WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
- while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)))
- cpu_relax();
-}
-
-/*
- * Conditionally acquire the specified rcu_data structure's
- * ->nocb_bypass_lock.
- */
-static bool rcu_nocb_bypass_trylock(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- return raw_spin_trylock(&rdp->nocb_bypass_lock);
-}
-
-/*
- * Release the specified rcu_data structure's ->nocb_bypass_lock.
- */
-static void rcu_nocb_bypass_unlock(struct rcu_data *rdp)
- __releases(&rdp->nocb_bypass_lock)
-{
- lockdep_assert_irqs_disabled();
- raw_spin_unlock(&rdp->nocb_bypass_lock);
-}
-
-/*
- * Acquire the specified rcu_data structure's ->nocb_lock, but only
- * if it corresponds to a no-CBs CPU.
- */
-static void rcu_nocb_lock(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- if (!rcu_rdp_is_offloaded(rdp))
- return;
- raw_spin_lock(&rdp->nocb_lock);
-}
-
-/*
- * Release the specified rcu_data structure's ->nocb_lock, but only
- * if it corresponds to a no-CBs CPU.
- */
-static void rcu_nocb_unlock(struct rcu_data *rdp)
-{
- if (rcu_rdp_is_offloaded(rdp)) {
- lockdep_assert_irqs_disabled();
- raw_spin_unlock(&rdp->nocb_lock);
- }
-}
-
-/*
- * Release the specified rcu_data structure's ->nocb_lock and restore
- * interrupts, but only if it corresponds to a no-CBs CPU.
- */
-static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
- unsigned long flags)
-{
- if (rcu_rdp_is_offloaded(rdp)) {
- lockdep_assert_irqs_disabled();
- raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
- } else {
- local_irq_restore(flags);
- }
-}
-
-/* Lockdep check that ->cblist may be safely accessed. */
-static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- if (rcu_rdp_is_offloaded(rdp))
- lockdep_assert_held(&rdp->nocb_lock);
-}
-
-/*
- * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
- * grace period.
- */
-static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
-{
- swake_up_all(sq);
-}
-
-static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
-{
- return &rnp->nocb_gp_wq[rcu_seq_ctr(rnp->gp_seq) & 0x1];
-}
-
-static void rcu_init_one_nocb(struct rcu_node *rnp)
-{
- init_swait_queue_head(&rnp->nocb_gp_wq[0]);
- init_swait_queue_head(&rnp->nocb_gp_wq[1]);
-}
-
-/* Is the specified CPU a no-CBs CPU? */
-bool rcu_is_nocb_cpu(int cpu)
-{
- if (cpumask_available(rcu_nocb_mask))
- return cpumask_test_cpu(cpu, rcu_nocb_mask);
- return false;
-}
-
-static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
- struct rcu_data *rdp,
- bool force, unsigned long flags)
- __releases(rdp_gp->nocb_gp_lock)
-{
- bool needwake = false;
-
- if (!READ_ONCE(rdp_gp->nocb_gp_kthread)) {
- raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("AlreadyAwake"));
- return false;
- }
-
- if (rdp_gp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
- WRITE_ONCE(rdp_gp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
- del_timer(&rdp_gp->nocb_timer);
- }
-
- if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
- WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
- needwake = true;
- }
- raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
- if (needwake) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
- wake_up_process(rdp_gp->nocb_gp_kthread);
- }
-
- return needwake;
-}
-
-/*
- * Kick the GP kthread for this NOCB group.
- */
-static bool wake_nocb_gp(struct rcu_data *rdp, bool force)
-{
- unsigned long flags;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
-
- raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
- return __wake_nocb_gp(rdp_gp, rdp, force, flags);
-}
-
-/*
- * Arrange to wake the GP kthread for this NOCB group at some future
- * time when it is safe to do so.
- */
-static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
- const char *reason)
-{
- unsigned long flags;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
-
- raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
-
- /*
- * Bypass wakeup overrides previous deferments. In case
- * of callback storm, no need to wake up too early.
- */
- if (waketype == RCU_NOCB_WAKE_BYPASS) {
- mod_timer(&rdp_gp->nocb_timer, jiffies + 2);
- WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
- } else {
- if (rdp_gp->nocb_defer_wakeup < RCU_NOCB_WAKE)
- mod_timer(&rdp_gp->nocb_timer, jiffies + 1);
- if (rdp_gp->nocb_defer_wakeup < waketype)
- WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
- }
-
- raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
-
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason);
-}
-
-/*
- * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
- * However, if there is a callback to be enqueued and if ->nocb_bypass
- * proves to be initially empty, just return false because the no-CB GP
- * kthread may need to be awakened in this case.
- *
- * Note that this function always returns true if rhp is NULL.
- */
-static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- unsigned long j)
-{
- struct rcu_cblist rcl;
-
- WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp));
- rcu_lockdep_assert_cblist_protected(rdp);
- lockdep_assert_held(&rdp->nocb_bypass_lock);
- if (rhp && !rcu_cblist_n_cbs(&rdp->nocb_bypass)) {
- raw_spin_unlock(&rdp->nocb_bypass_lock);
- return false;
- }
- /* Note: ->cblist.len already accounts for ->nocb_bypass contents. */
- if (rhp)
- rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
- rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
- rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
- WRITE_ONCE(rdp->nocb_bypass_first, j);
- rcu_nocb_bypass_unlock(rdp);
- return true;
-}
-
-/*
- * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
- * However, if there is a callback to be enqueued and if ->nocb_bypass
- * proves to be initially empty, just return false because the no-CB GP
- * kthread may need to be awakened in this case.
- *
- * Note that this function always returns true if rhp is NULL.
- */
-static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- unsigned long j)
-{
- if (!rcu_rdp_is_offloaded(rdp))
- return true;
- rcu_lockdep_assert_cblist_protected(rdp);
- rcu_nocb_bypass_lock(rdp);
- return rcu_nocb_do_flush_bypass(rdp, rhp, j);
-}
-
-/*
- * If the ->nocb_bypass_lock is immediately available, flush the
- * ->nocb_bypass queue into ->cblist.
- */
-static void rcu_nocb_try_flush_bypass(struct rcu_data *rdp, unsigned long j)
-{
- rcu_lockdep_assert_cblist_protected(rdp);
- if (!rcu_rdp_is_offloaded(rdp) ||
- !rcu_nocb_bypass_trylock(rdp))
- return;
- WARN_ON_ONCE(!rcu_nocb_do_flush_bypass(rdp, NULL, j));
-}
-
-/*
- * See whether it is appropriate to use the ->nocb_bypass list in order
- * to control contention on ->nocb_lock. A limited number of direct
- * enqueues are permitted into ->cblist per jiffy. If ->nocb_bypass
- * is non-empty, further callbacks must be placed into ->nocb_bypass,
- * otherwise rcu_barrier() breaks. Use rcu_nocb_flush_bypass() to switch
- * back to direct use of ->cblist. However, ->nocb_bypass should not be
- * used if ->cblist is empty, because otherwise callbacks can be stranded
- * on ->nocb_bypass because we cannot count on the current CPU ever again
- * invoking call_rcu(). The general rule is that if ->nocb_bypass is
- * non-empty, the corresponding no-CBs grace-period kthread must not be
- * in an indefinite sleep state.
- *
- * Finally, it is not permitted to use the bypass during early boot,
- * as doing so would confuse the auto-initialization code. Besides
- * which, there is no point in worrying about lock contention while
- * there is only one CPU in operation.
- */
-static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- bool *was_alldone, unsigned long flags)
-{
- unsigned long c;
- unsigned long cur_gp_seq;
- unsigned long j = jiffies;
- long ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
-
- lockdep_assert_irqs_disabled();
-
- // Pure softirq/rcuc based processing: no bypassing, no
- // locking.
- if (!rcu_rdp_is_offloaded(rdp)) {
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- return false;
- }
-
- // In the process of (de-)offloading: no bypassing, but
- // locking.
- if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
- rcu_nocb_lock(rdp);
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- return false; /* Not offloaded, no bypassing. */
- }
-
- // Don't use ->nocb_bypass during early boot.
- if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) {
- rcu_nocb_lock(rdp);
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- return false;
- }
-
- // If we have advanced to a new jiffy, reset counts to allow
- // moving back from ->nocb_bypass to ->cblist.
- if (j == rdp->nocb_nobypass_last) {
- c = rdp->nocb_nobypass_count + 1;
- } else {
- WRITE_ONCE(rdp->nocb_nobypass_last, j);
- c = rdp->nocb_nobypass_count - nocb_nobypass_lim_per_jiffy;
- if (ULONG_CMP_LT(rdp->nocb_nobypass_count,
- nocb_nobypass_lim_per_jiffy))
- c = 0;
- else if (c > nocb_nobypass_lim_per_jiffy)
- c = nocb_nobypass_lim_per_jiffy;
- }
- WRITE_ONCE(rdp->nocb_nobypass_count, c);
-
- // If there hasn't yet been all that many ->cblist enqueues
- // this jiffy, tell the caller to enqueue onto ->cblist. But flush
- // ->nocb_bypass first.
- if (rdp->nocb_nobypass_count < nocb_nobypass_lim_per_jiffy) {
- rcu_nocb_lock(rdp);
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- if (*was_alldone)
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstQ"));
- WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, j));
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
- return false; // Caller must enqueue the callback.
- }
-
- // If ->nocb_bypass has been used too long or is too full,
- // flush ->nocb_bypass to ->cblist.
- if ((ncbs && j != READ_ONCE(rdp->nocb_bypass_first)) ||
- ncbs >= qhimark) {
- rcu_nocb_lock(rdp);
- if (!rcu_nocb_flush_bypass(rdp, rhp, j)) {
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- if (*was_alldone)
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstQ"));
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
- return false; // Caller must enqueue the callback.
- }
- if (j != rdp->nocb_gp_adv_time &&
- rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
- rcu_advance_cbs_nowake(rdp->mynode, rdp);
- rdp->nocb_gp_adv_time = j;
- }
- rcu_nocb_unlock_irqrestore(rdp, flags);
- return true; // Callback already enqueued.
- }
-
- // We need to use the bypass.
- rcu_nocb_wait_contended(rdp);
- rcu_nocb_bypass_lock(rdp);
- ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
- rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
- rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
- if (!ncbs) {
- WRITE_ONCE(rdp->nocb_bypass_first, j);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("FirstBQ"));
- }
- rcu_nocb_bypass_unlock(rdp);
- smp_mb(); /* Order enqueue before wake. */
- if (ncbs) {
- local_irq_restore(flags);
- } else {
- // No-CBs GP kthread might be indefinitely asleep, if so, wake.
- rcu_nocb_lock(rdp); // Rare during call_rcu() flood.
- if (!rcu_segcblist_pend_cbs(&rdp->cblist)) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstBQwake"));
- __call_rcu_nocb_wake(rdp, true, flags);
- } else {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstBQnoWake"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- }
- }
- return true; // Callback already enqueued.
-}
-
-/*
- * Awaken the no-CBs grace-period kthread if needed, either due to it
- * legitimately being asleep or due to overload conditions.
- *
- * If warranted, also wake up the kthread servicing this CPUs queues.
- */
-static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
- unsigned long flags)
- __releases(rdp->nocb_lock)
-{
- unsigned long cur_gp_seq;
- unsigned long j;
- long len;
- struct task_struct *t;
-
- // If we are being polled or there is no kthread, just leave.
- t = READ_ONCE(rdp->nocb_gp_kthread);
- if (rcu_nocb_poll || !t) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("WakeNotPoll"));
- return;
- }
- // Need to actually to a wakeup.
- len = rcu_segcblist_n_cbs(&rdp->cblist);
- if (was_alldone) {
- rdp->qlen_last_fqs_check = len;
- if (!irqs_disabled_flags(flags)) {
- /* ... if queue was empty ... */
- rcu_nocb_unlock_irqrestore(rdp, flags);
- wake_nocb_gp(rdp, false);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("WakeEmpty"));
- } else {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
- TPS("WakeEmptyIsDeferred"));
- }
- } else if (len > rdp->qlen_last_fqs_check + qhimark) {
- /* ... or if many callbacks queued. */
- rdp->qlen_last_fqs_check = len;
- j = jiffies;
- if (j != rdp->nocb_gp_adv_time &&
- rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
- rcu_advance_cbs_nowake(rdp->mynode, rdp);
- rdp->nocb_gp_adv_time = j;
- }
- smp_mb(); /* Enqueue before timer_pending(). */
- if ((rdp->nocb_cb_sleep ||
- !rcu_segcblist_ready_cbs(&rdp->cblist)) &&
- !timer_pending(&rdp->nocb_timer)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE,
- TPS("WakeOvfIsDeferred"));
- } else {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
- }
- } else {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
- }
- return;
-}
-
-/*
- * Check if we ignore this rdp.
- *
- * We check that without holding the nocb lock but
- * we make sure not to miss a freshly offloaded rdp
- * with the current ordering:
- *
- * rdp_offload_toggle() nocb_gp_enabled_cb()
- * ------------------------- ----------------------------
- * WRITE flags LOCK nocb_gp_lock
- * LOCK nocb_gp_lock READ/WRITE nocb_gp_sleep
- * READ/WRITE nocb_gp_sleep UNLOCK nocb_gp_lock
- * UNLOCK nocb_gp_lock READ flags
- */
-static inline bool nocb_gp_enabled_cb(struct rcu_data *rdp)
-{
- u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_GP;
-
- return rcu_segcblist_test_flags(&rdp->cblist, flags);
-}
-
-static inline bool nocb_gp_update_state_deoffloading(struct rcu_data *rdp,
- bool *needwake_state)
-{
- struct rcu_segcblist *cblist = &rdp->cblist;
-
- if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) {
- if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) {
- rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_GP);
- if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
- *needwake_state = true;
- }
- return false;
- }
-
- /*
- * De-offloading. Clear our flag and notify the de-offload worker.
- * We will ignore this rdp until it ever gets re-offloaded.
- */
- WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP));
- rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_GP);
- if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
- *needwake_state = true;
- return true;
-}
-
-
-/*
- * No-CBs GP kthreads come here to wait for additional callbacks to show up
- * or for grace periods to end.
- */
-static void nocb_gp_wait(struct rcu_data *my_rdp)
-{
- bool bypass = false;
- long bypass_ncbs;
- int __maybe_unused cpu = my_rdp->cpu;
- unsigned long cur_gp_seq;
- unsigned long flags;
- bool gotcbs = false;
- unsigned long j = jiffies;
- bool needwait_gp = false; // This prevents actual uninitialized use.
- bool needwake;
- bool needwake_gp;
- struct rcu_data *rdp;
- struct rcu_node *rnp;
- unsigned long wait_gp_seq = 0; // Suppress "use uninitialized" warning.
- bool wasempty = false;
-
- /*
- * Each pass through the following loop checks for CBs and for the
- * nearest grace period (if any) to wait for next. The CB kthreads
- * and the global grace-period kthread are awakened if needed.
- */
- WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp);
- for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) {
- bool needwake_state = false;
-
- if (!nocb_gp_enabled_cb(rdp))
- continue;
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
- rcu_nocb_lock_irqsave(rdp, flags);
- if (nocb_gp_update_state_deoffloading(rdp, &needwake_state)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake_state)
- swake_up_one(&rdp->nocb_state_wq);
- continue;
- }
- bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
- if (bypass_ncbs &&
- (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) ||
- bypass_ncbs > 2 * qhimark)) {
- // Bypass full or old, so flush it.
- (void)rcu_nocb_try_flush_bypass(rdp, j);
- bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
- } else if (!bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake_state)
- swake_up_one(&rdp->nocb_state_wq);
- continue; /* No callbacks here, try next. */
- }
- if (bypass_ncbs) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("Bypass"));
- bypass = true;
- }
- rnp = rdp->mynode;
-
- // Advance callbacks if helpful and low contention.
- needwake_gp = false;
- if (!rcu_segcblist_restempty(&rdp->cblist,
- RCU_NEXT_READY_TAIL) ||
- (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rnp->gp_seq, cur_gp_seq))) {
- raw_spin_lock_rcu_node(rnp); /* irqs disabled. */
- needwake_gp = rcu_advance_cbs(rnp, rdp);
- wasempty = rcu_segcblist_restempty(&rdp->cblist,
- RCU_NEXT_READY_TAIL);
- raw_spin_unlock_rcu_node(rnp); /* irqs disabled. */
- }
- // Need to wait on some grace period?
- WARN_ON_ONCE(wasempty &&
- !rcu_segcblist_restempty(&rdp->cblist,
- RCU_NEXT_READY_TAIL));
- if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq)) {
- if (!needwait_gp ||
- ULONG_CMP_LT(cur_gp_seq, wait_gp_seq))
- wait_gp_seq = cur_gp_seq;
- needwait_gp = true;
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("NeedWaitGP"));
- }
- if (rcu_segcblist_ready_cbs(&rdp->cblist)) {
- needwake = rdp->nocb_cb_sleep;
- WRITE_ONCE(rdp->nocb_cb_sleep, false);
- smp_mb(); /* CB invocation -after- GP end. */
- } else {
- needwake = false;
- }
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake) {
- swake_up_one(&rdp->nocb_cb_wq);
- gotcbs = true;
- }
- if (needwake_gp)
- rcu_gp_kthread_wake();
- if (needwake_state)
- swake_up_one(&rdp->nocb_state_wq);
- }
-
- my_rdp->nocb_gp_bypass = bypass;
- my_rdp->nocb_gp_gp = needwait_gp;
- my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
-
- if (bypass && !rcu_nocb_poll) {
- // At least one child with non-empty ->nocb_bypass, so set
- // timer in order to avoid stranding its callbacks.
- wake_nocb_gp_defer(my_rdp, RCU_NOCB_WAKE_BYPASS,
- TPS("WakeBypassIsDeferred"));
- }
- if (rcu_nocb_poll) {
- /* Polling, so trace if first poll in the series. */
- if (gotcbs)
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll"));
- schedule_timeout_idle(1);
- } else if (!needwait_gp) {
- /* Wait for callbacks to appear. */
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Sleep"));
- swait_event_interruptible_exclusive(my_rdp->nocb_gp_wq,
- !READ_ONCE(my_rdp->nocb_gp_sleep));
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("EndSleep"));
- } else {
- rnp = my_rdp->mynode;
- trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("StartWait"));
- swait_event_interruptible_exclusive(
- rnp->nocb_gp_wq[rcu_seq_ctr(wait_gp_seq) & 0x1],
- rcu_seq_done(&rnp->gp_seq, wait_gp_seq) ||
- !READ_ONCE(my_rdp->nocb_gp_sleep));
- trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("EndWait"));
- }
- if (!rcu_nocb_poll) {
- raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
- if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
- WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
- del_timer(&my_rdp->nocb_timer);
- }
- WRITE_ONCE(my_rdp->nocb_gp_sleep, true);
- raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
- }
- my_rdp->nocb_gp_seq = -1;
- WARN_ON(signal_pending(current));
-}
-
-/*
- * No-CBs grace-period-wait kthread. There is one of these per group
- * of CPUs, but only once at least one CPU in that group has come online
- * at least once since boot. This kthread checks for newly posted
- * callbacks from any of the CPUs it is responsible for, waits for a
- * grace period, then awakens all of the rcu_nocb_cb_kthread() instances
- * that then have callback-invocation work to do.
- */
-static int rcu_nocb_gp_kthread(void *arg)
-{
- struct rcu_data *rdp = arg;
-
- for (;;) {
- WRITE_ONCE(rdp->nocb_gp_loops, rdp->nocb_gp_loops + 1);
- nocb_gp_wait(rdp);
- cond_resched_tasks_rcu_qs();
- }
- return 0;
-}
-
-static inline bool nocb_cb_can_run(struct rcu_data *rdp)
-{
- u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_CB;
- return rcu_segcblist_test_flags(&rdp->cblist, flags);
-}
-
-static inline bool nocb_cb_wait_cond(struct rcu_data *rdp)
-{
- return nocb_cb_can_run(rdp) && !READ_ONCE(rdp->nocb_cb_sleep);
-}
-
-/*
- * Invoke any ready callbacks from the corresponding no-CBs CPU,
- * then, if there are no more, wait for more to appear.
- */
-static void nocb_cb_wait(struct rcu_data *rdp)
-{
- struct rcu_segcblist *cblist = &rdp->cblist;
- unsigned long cur_gp_seq;
- unsigned long flags;
- bool needwake_state = false;
- bool needwake_gp = false;
- bool can_sleep = true;
- struct rcu_node *rnp = rdp->mynode;
-
- local_irq_save(flags);
- rcu_momentary_dyntick_idle();
- local_irq_restore(flags);
- /*
- * Disable BH to provide the expected environment. Also, when
- * transitioning to/from NOCB mode, a self-requeuing callback might
- * be invoked from softirq. A short grace period could cause both
- * instances of this callback would execute concurrently.
- */
- local_bh_disable();
- rcu_do_batch(rdp);
- local_bh_enable();
- lockdep_assert_irqs_enabled();
- rcu_nocb_lock_irqsave(rdp, flags);
- if (rcu_segcblist_nextgp(cblist, &cur_gp_seq) &&
- rcu_seq_done(&rnp->gp_seq, cur_gp_seq) &&
- raw_spin_trylock_rcu_node(rnp)) { /* irqs already disabled. */
- needwake_gp = rcu_advance_cbs(rdp->mynode, rdp);
- raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
- }
-
- if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) {
- if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)) {
- rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_CB);
- if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP))
- needwake_state = true;
- }
- if (rcu_segcblist_ready_cbs(cblist))
- can_sleep = false;
- } else {
- /*
- * De-offloading. Clear our flag and notify the de-offload worker.
- * We won't touch the callbacks and keep sleeping until we ever
- * get re-offloaded.
- */
- WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB));
- rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_CB);
- if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP))
- needwake_state = true;
- }
-
- WRITE_ONCE(rdp->nocb_cb_sleep, can_sleep);
-
- if (rdp->nocb_cb_sleep)
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep"));
-
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake_gp)
- rcu_gp_kthread_wake();
-
- if (needwake_state)
- swake_up_one(&rdp->nocb_state_wq);
-
- do {
- swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
- nocb_cb_wait_cond(rdp));
-
- // VVV Ensure CB invocation follows _sleep test.
- if (smp_load_acquire(&rdp->nocb_cb_sleep)) { // ^^^
- WARN_ON(signal_pending(current));
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
- }
- } while (!nocb_cb_can_run(rdp));
-}
-
-/*
- * Per-rcu_data kthread, but only for no-CBs CPUs. Repeatedly invoke
- * nocb_cb_wait() to do the dirty work.
- */
-static int rcu_nocb_cb_kthread(void *arg)
-{
- struct rcu_data *rdp = arg;
-
- // Each pass through this loop does one callback batch, and,
- // if there are no more ready callbacks, waits for them.
- for (;;) {
- nocb_cb_wait(rdp);
- cond_resched_tasks_rcu_qs();
- }
- return 0;
-}
-
-/* Is a deferred wakeup of rcu_nocb_kthread() required? */
-static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
-{
- return READ_ONCE(rdp->nocb_defer_wakeup) >= level;
-}
-
-/* Do a deferred wakeup of rcu_nocb_kthread(). */
-static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp_gp,
- struct rcu_data *rdp, int level,
- unsigned long flags)
- __releases(rdp_gp->nocb_gp_lock)
-{
- int ndw;
- int ret;
-
- if (!rcu_nocb_need_deferred_wakeup(rdp_gp, level)) {
- raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
- return false;
- }
-
- ndw = rdp_gp->nocb_defer_wakeup;
- ret = __wake_nocb_gp(rdp_gp, rdp, ndw == RCU_NOCB_WAKE_FORCE, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake"));
-
- return ret;
-}
-
-/* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */
-static void do_nocb_deferred_wakeup_timer(struct timer_list *t)
-{
- unsigned long flags;
- struct rcu_data *rdp = from_timer(rdp, t, nocb_timer);
-
- WARN_ON_ONCE(rdp->nocb_gp_rdp != rdp);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Timer"));
-
- raw_spin_lock_irqsave(&rdp->nocb_gp_lock, flags);
- smp_mb__after_spinlock(); /* Timer expire before wakeup. */
- do_nocb_deferred_wakeup_common(rdp, rdp, RCU_NOCB_WAKE_BYPASS, flags);
-}
-
-/*
- * Do a deferred wakeup of rcu_nocb_kthread() from fastpath.
- * This means we do an inexact common-case check. Note that if
- * we miss, ->nocb_timer will eventually clean things up.
- */
-static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
-{
- unsigned long flags;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
-
- if (!rdp_gp || !rcu_nocb_need_deferred_wakeup(rdp_gp, RCU_NOCB_WAKE))
- return false;
-
- raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
- return do_nocb_deferred_wakeup_common(rdp_gp, rdp, RCU_NOCB_WAKE, flags);
-}
-
-void rcu_nocb_flush_deferred_wakeup(void)
-{
- do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data));
-}
-EXPORT_SYMBOL_GPL(rcu_nocb_flush_deferred_wakeup);
-
-static int rdp_offload_toggle(struct rcu_data *rdp,
- bool offload, unsigned long flags)
- __releases(rdp->nocb_lock)
-{
- struct rcu_segcblist *cblist = &rdp->cblist;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
- bool wake_gp = false;
-
- rcu_segcblist_offload(cblist, offload);
-
- if (rdp->nocb_cb_sleep)
- rdp->nocb_cb_sleep = false;
- rcu_nocb_unlock_irqrestore(rdp, flags);
-
- /*
- * Ignore former value of nocb_cb_sleep and force wake up as it could
- * have been spuriously set to false already.
- */
- swake_up_one(&rdp->nocb_cb_wq);
-
- raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
- if (rdp_gp->nocb_gp_sleep) {
- rdp_gp->nocb_gp_sleep = false;
- wake_gp = true;
- }
- raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
-
- if (wake_gp)
- wake_up_process(rdp_gp->nocb_gp_kthread);
-
- return 0;
-}
-
-static long rcu_nocb_rdp_deoffload(void *arg)
-{
- struct rcu_data *rdp = arg;
- struct rcu_segcblist *cblist = &rdp->cblist;
- unsigned long flags;
- int ret;
-
- WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
-
- pr_info("De-offloading %d\n", rdp->cpu);
-
- rcu_nocb_lock_irqsave(rdp, flags);
- /*
- * Flush once and for all now. This suffices because we are
- * running on the target CPU holding ->nocb_lock (thus having
- * interrupts disabled), and because rdp_offload_toggle()
- * invokes rcu_segcblist_offload(), which clears SEGCBLIST_OFFLOADED.
- * Thus future calls to rcu_segcblist_completely_offloaded() will
- * return false, which means that future calls to rcu_nocb_try_bypass()
- * will refuse to put anything into the bypass.
- */
- WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies));
- ret = rdp_offload_toggle(rdp, false, flags);
- swait_event_exclusive(rdp->nocb_state_wq,
- !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
- SEGCBLIST_KTHREAD_GP));
- /*
- * Lock one last time to acquire latest callback updates from kthreads
- * so we can later handle callbacks locally without locking.
- */
- rcu_nocb_lock_irqsave(rdp, flags);
- /*
- * Theoretically we could set SEGCBLIST_SOFTIRQ_ONLY after the nocb
- * lock is released but how about being paranoid for once?
- */
- rcu_segcblist_set_flags(cblist, SEGCBLIST_SOFTIRQ_ONLY);
- /*
- * With SEGCBLIST_SOFTIRQ_ONLY, we can't use
- * rcu_nocb_unlock_irqrestore() anymore.
- */
- raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
-
- /* Sanity check */
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
-
-
- return ret;
-}
-
-int rcu_nocb_cpu_deoffload(int cpu)
-{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
- int ret = 0;
-
- mutex_lock(&rcu_state.barrier_mutex);
- cpus_read_lock();
- if (rcu_rdp_is_offloaded(rdp)) {
- if (cpu_online(cpu)) {
- ret = work_on_cpu(cpu, rcu_nocb_rdp_deoffload, rdp);
- if (!ret)
- cpumask_clear_cpu(cpu, rcu_nocb_mask);
- } else {
- pr_info("NOCB: Can't CB-deoffload an offline CPU\n");
- ret = -EINVAL;
- }
- }
- cpus_read_unlock();
- mutex_unlock(&rcu_state.barrier_mutex);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(rcu_nocb_cpu_deoffload);
-
-static long rcu_nocb_rdp_offload(void *arg)
-{
- struct rcu_data *rdp = arg;
- struct rcu_segcblist *cblist = &rdp->cblist;
- unsigned long flags;
- int ret;
-
- WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
- /*
- * For now we only support re-offload, ie: the rdp must have been
- * offloaded on boot first.
- */
- if (!rdp->nocb_gp_rdp)
- return -EINVAL;
-
- pr_info("Offloading %d\n", rdp->cpu);
- /*
- * Can't use rcu_nocb_lock_irqsave() while we are in
- * SEGCBLIST_SOFTIRQ_ONLY mode.
- */
- raw_spin_lock_irqsave(&rdp->nocb_lock, flags);
-
- /*
- * We didn't take the nocb lock while working on the
- * rdp->cblist in SEGCBLIST_SOFTIRQ_ONLY mode.
- * Every modifications that have been done previously on
- * rdp->cblist must be visible remotely by the nocb kthreads
- * upon wake up after reading the cblist flags.
- *
- * The layout against nocb_lock enforces that ordering:
- *
- * __rcu_nocb_rdp_offload() nocb_cb_wait()/nocb_gp_wait()
- * ------------------------- ----------------------------
- * WRITE callbacks rcu_nocb_lock()
- * rcu_nocb_lock() READ flags
- * WRITE flags READ callbacks
- * rcu_nocb_unlock() rcu_nocb_unlock()
- */
- ret = rdp_offload_toggle(rdp, true, flags);
- swait_event_exclusive(rdp->nocb_state_wq,
- rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) &&
- rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP));
-
- return ret;
-}
-
-int rcu_nocb_cpu_offload(int cpu)
-{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
- int ret = 0;
-
- mutex_lock(&rcu_state.barrier_mutex);
- cpus_read_lock();
- if (!rcu_rdp_is_offloaded(rdp)) {
- if (cpu_online(cpu)) {
- ret = work_on_cpu(cpu, rcu_nocb_rdp_offload, rdp);
- if (!ret)
- cpumask_set_cpu(cpu, rcu_nocb_mask);
- } else {
- pr_info("NOCB: Can't CB-offload an offline CPU\n");
- ret = -EINVAL;
- }
- }
- cpus_read_unlock();
- mutex_unlock(&rcu_state.barrier_mutex);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
-
-void __init rcu_init_nohz(void)
-{
- int cpu;
- bool need_rcu_nocb_mask = false;
- struct rcu_data *rdp;
-
-#if defined(CONFIG_NO_HZ_FULL)
- if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask))
- need_rcu_nocb_mask = true;
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
- if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
- if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
- pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
- return;
- }
- }
- if (!cpumask_available(rcu_nocb_mask))
- return;
-
-#if defined(CONFIG_NO_HZ_FULL)
- if (tick_nohz_full_running)
- cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
- if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
- pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
- cpumask_and(rcu_nocb_mask, cpu_possible_mask,
- rcu_nocb_mask);
- }
- if (cpumask_empty(rcu_nocb_mask))
- pr_info("\tOffload RCU callbacks from CPUs: (none).\n");
- else
- pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n",
- cpumask_pr_args(rcu_nocb_mask));
- if (rcu_nocb_poll)
- pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
-
- for_each_cpu(cpu, rcu_nocb_mask) {
- rdp = per_cpu_ptr(&rcu_data, cpu);
- if (rcu_segcblist_empty(&rdp->cblist))
- rcu_segcblist_init(&rdp->cblist);
- rcu_segcblist_offload(&rdp->cblist, true);
- rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB);
- rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_GP);
- }
- rcu_organize_nocb_kthreads();
-}
-
-/* Initialize per-rcu_data variables for no-CBs CPUs. */
-static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
-{
- init_swait_queue_head(&rdp->nocb_cb_wq);
- init_swait_queue_head(&rdp->nocb_gp_wq);
- init_swait_queue_head(&rdp->nocb_state_wq);
- raw_spin_lock_init(&rdp->nocb_lock);
- raw_spin_lock_init(&rdp->nocb_bypass_lock);
- raw_spin_lock_init(&rdp->nocb_gp_lock);
- timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0);
- rcu_cblist_init(&rdp->nocb_bypass);
-}
-
-/*
- * If the specified CPU is a no-CBs CPU that does not already have its
- * rcuo CB kthread, spawn it. Additionally, if the rcuo GP kthread
- * for this CPU's group has not yet been created, spawn it as well.
- */
-static void rcu_spawn_one_nocb_kthread(int cpu)
-{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
- struct rcu_data *rdp_gp;
- struct task_struct *t;
-
- /*
- * If this isn't a no-CBs CPU or if it already has an rcuo kthread,
- * then nothing to do.
- */
- if (!rcu_is_nocb_cpu(cpu) || rdp->nocb_cb_kthread)
- return;
-
- /* If we didn't spawn the GP kthread first, reorganize! */
- rdp_gp = rdp->nocb_gp_rdp;
- if (!rdp_gp->nocb_gp_kthread) {
- t = kthread_run(rcu_nocb_gp_kthread, rdp_gp,
- "rcuog/%d", rdp_gp->cpu);
- if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo GP kthread, OOM is now expected behavior\n", __func__))
- return;
- WRITE_ONCE(rdp_gp->nocb_gp_kthread, t);
- }
-
- /* Spawn the kthread for this CPU. */
- t = kthread_run(rcu_nocb_cb_kthread, rdp,
- "rcuo%c/%d", rcu_state.abbr, cpu);
- if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__))
- return;
- WRITE_ONCE(rdp->nocb_cb_kthread, t);
- WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
-}
-
-/*
- * If the specified CPU is a no-CBs CPU that does not already have its
- * rcuo kthread, spawn it.
- */
-static void rcu_spawn_cpu_nocb_kthread(int cpu)
-{
- if (rcu_scheduler_fully_active)
- rcu_spawn_one_nocb_kthread(cpu);
-}
-
-/*
- * Once the scheduler is running, spawn rcuo kthreads for all online
- * no-CBs CPUs. This assumes that the early_initcall()s happen before
- * non-boot CPUs come online -- if this changes, we will need to add
- * some mutual exclusion.
- */
-static void __init rcu_spawn_nocb_kthreads(void)
-{
- int cpu;
-
- for_each_online_cpu(cpu)
- rcu_spawn_cpu_nocb_kthread(cpu);
-}
-
-/* How many CB CPU IDs per GP kthread? Default of -1 for sqrt(nr_cpu_ids). */
-static int rcu_nocb_gp_stride = -1;
-module_param(rcu_nocb_gp_stride, int, 0444);
-
-/*
- * Initialize GP-CB relationships for all no-CBs CPU.
- */
-static void __init rcu_organize_nocb_kthreads(void)
-{
- int cpu;
- bool firsttime = true;
- bool gotnocbs = false;
- bool gotnocbscbs = true;
- int ls = rcu_nocb_gp_stride;
- int nl = 0; /* Next GP kthread. */
- struct rcu_data *rdp;
- struct rcu_data *rdp_gp = NULL; /* Suppress misguided gcc warn. */
- struct rcu_data *rdp_prev = NULL;
-
- if (!cpumask_available(rcu_nocb_mask))
- return;
- if (ls == -1) {
- ls = nr_cpu_ids / int_sqrt(nr_cpu_ids);
- rcu_nocb_gp_stride = ls;
- }
-
- /*
- * Each pass through this loop sets up one rcu_data structure.
- * Should the corresponding CPU come online in the future, then
- * we will spawn the needed set of rcu_nocb_kthread() kthreads.
- */
- for_each_cpu(cpu, rcu_nocb_mask) {
- rdp = per_cpu_ptr(&rcu_data, cpu);
- if (rdp->cpu >= nl) {
- /* New GP kthread, set up for CBs & next GP. */
- gotnocbs = true;
- nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls;
- rdp->nocb_gp_rdp = rdp;
- rdp_gp = rdp;
- if (dump_tree) {
- if (!firsttime)
- pr_cont("%s\n", gotnocbscbs
- ? "" : " (self only)");
- gotnocbscbs = false;
- firsttime = false;
- pr_alert("%s: No-CB GP kthread CPU %d:",
- __func__, cpu);
- }
- } else {
- /* Another CB kthread, link to previous GP kthread. */
- gotnocbscbs = true;
- rdp->nocb_gp_rdp = rdp_gp;
- rdp_prev->nocb_next_cb_rdp = rdp;
- if (dump_tree)
- pr_cont(" %d", cpu);
- }
- rdp_prev = rdp;
- }
- if (gotnocbs && dump_tree)
- pr_cont("%s\n", gotnocbscbs ? "" : " (self only)");
-}
-
-/*
- * Bind the current task to the offloaded CPUs. If there are no offloaded
- * CPUs, leave the task unbound. Splat if the bind attempt fails.
- */
-void rcu_bind_current_to_nocb(void)
-{
- if (cpumask_available(rcu_nocb_mask) && cpumask_weight(rcu_nocb_mask))
- WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask));
-}
-EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb);
-
-// The ->on_cpu field is available only in CONFIG_SMP=y, so...
-#ifdef CONFIG_SMP
-static char *show_rcu_should_be_on_cpu(struct task_struct *tsp)
-{
- return tsp && task_is_running(tsp) && !tsp->on_cpu ? "!" : "";
-}
-#else // #ifdef CONFIG_SMP
-static char *show_rcu_should_be_on_cpu(struct task_struct *tsp)
-{
- return "";
-}
-#endif // #else #ifdef CONFIG_SMP
-
-/*
- * Dump out nocb grace-period kthread state for the specified rcu_data
- * structure.
- */
-static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
-{
- struct rcu_node *rnp = rdp->mynode;
-
- pr_info("nocb GP %d %c%c%c%c%c %c[%c%c] %c%c:%ld rnp %d:%d %lu %c CPU %d%s\n",
- rdp->cpu,
- "kK"[!!rdp->nocb_gp_kthread],
- "lL"[raw_spin_is_locked(&rdp->nocb_gp_lock)],
- "dD"[!!rdp->nocb_defer_wakeup],
- "tT"[timer_pending(&rdp->nocb_timer)],
- "sS"[!!rdp->nocb_gp_sleep],
- ".W"[swait_active(&rdp->nocb_gp_wq)],
- ".W"[swait_active(&rnp->nocb_gp_wq[0])],
- ".W"[swait_active(&rnp->nocb_gp_wq[1])],
- ".B"[!!rdp->nocb_gp_bypass],
- ".G"[!!rdp->nocb_gp_gp],
- (long)rdp->nocb_gp_seq,
- rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
- rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
- rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
- show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
-}
-
-/* Dump out nocb kthread state for the specified rcu_data structure. */
-static void show_rcu_nocb_state(struct rcu_data *rdp)
-{
- char bufw[20];
- char bufr[20];
- struct rcu_segcblist *rsclp = &rdp->cblist;
- bool waslocked;
- bool wassleep;
-
- if (rdp->nocb_gp_rdp == rdp)
- show_rcu_nocb_gp_state(rdp);
-
- sprintf(bufw, "%ld", rsclp->gp_seq[RCU_WAIT_TAIL]);
- sprintf(bufr, "%ld", rsclp->gp_seq[RCU_NEXT_READY_TAIL]);
- pr_info(" CB %d^%d->%d %c%c%c%c%c%c F%ld L%ld C%d %c%c%s%c%s%c%c q%ld %c CPU %d%s\n",
- rdp->cpu, rdp->nocb_gp_rdp->cpu,
- rdp->nocb_next_cb_rdp ? rdp->nocb_next_cb_rdp->cpu : -1,
- "kK"[!!rdp->nocb_cb_kthread],
- "bB"[raw_spin_is_locked(&rdp->nocb_bypass_lock)],
- "cC"[!!atomic_read(&rdp->nocb_lock_contended)],
- "lL"[raw_spin_is_locked(&rdp->nocb_lock)],
- "sS"[!!rdp->nocb_cb_sleep],
- ".W"[swait_active(&rdp->nocb_cb_wq)],
- jiffies - rdp->nocb_bypass_first,
- jiffies - rdp->nocb_nobypass_last,
- rdp->nocb_nobypass_count,
- ".D"[rcu_segcblist_ready_cbs(rsclp)],
- ".W"[!rcu_segcblist_segempty(rsclp, RCU_WAIT_TAIL)],
- rcu_segcblist_segempty(rsclp, RCU_WAIT_TAIL) ? "" : bufw,
- ".R"[!rcu_segcblist_segempty(rsclp, RCU_NEXT_READY_TAIL)],
- rcu_segcblist_segempty(rsclp, RCU_NEXT_READY_TAIL) ? "" : bufr,
- ".N"[!rcu_segcblist_segempty(rsclp, RCU_NEXT_TAIL)],
- ".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
- rcu_segcblist_n_cbs(&rdp->cblist),
- rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
- rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
- show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
-
- /* It is OK for GP kthreads to have GP state. */
- if (rdp->nocb_gp_rdp == rdp)
- return;
-
- waslocked = raw_spin_is_locked(&rdp->nocb_gp_lock);
- wassleep = swait_active(&rdp->nocb_gp_wq);
- if (!rdp->nocb_gp_sleep && !waslocked && !wassleep)
- return; /* Nothing untoward. */
-
- pr_info(" nocb GP activity on CB-only CPU!!! %c%c%c %c\n",
- "lL"[waslocked],
- "dD"[!!rdp->nocb_defer_wakeup],
- "sS"[!!rdp->nocb_gp_sleep],
- ".W"[wassleep]);
-}
-
-#else /* #ifdef CONFIG_RCU_NOCB_CPU */
-
-/* No ->nocb_lock to acquire. */
-static void rcu_nocb_lock(struct rcu_data *rdp)
-{
-}
-
-/* No ->nocb_lock to release. */
-static void rcu_nocb_unlock(struct rcu_data *rdp)
-{
-}
-
-/* No ->nocb_lock to release. */
-static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
- unsigned long flags)
-{
- local_irq_restore(flags);
-}
-
-/* Lockdep check that ->cblist may be safely accessed. */
-static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
-}
-
-static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
-{
-}
-
-static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
-{
- return NULL;
-}
-
-static void rcu_init_one_nocb(struct rcu_node *rnp)
-{
-}
-
-static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- unsigned long j)
-{
- return true;
-}
-
-static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- bool *was_alldone, unsigned long flags)
-{
- return false;
-}
-
-static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
- unsigned long flags)
-{
- WARN_ON_ONCE(1); /* Should be dead code! */
-}
-
-static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
-{
-}
-
-static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
-{
- return false;
-}
-
-static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
-{
- return false;
-}
-
-static void rcu_spawn_cpu_nocb_kthread(int cpu)
-{
-}
-
-static void __init rcu_spawn_nocb_kthreads(void)
-{
-}
-
-static void show_rcu_nocb_state(struct rcu_data *rdp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
-
/*
* Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the
* grace-period kthread will do force_quiescent_state() processing?
@@ -2982,17 +1498,17 @@
/* Turn on heavyweight RCU tasks trace readers on idle/user entry. */
static void rcu_dynticks_task_trace_enter(void)
{
-#ifdef CONFIG_TASKS_RCU_TRACE
+#ifdef CONFIG_TASKS_TRACE_RCU
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
current->trc_reader_special.b.need_mb = true;
-#endif /* #ifdef CONFIG_TASKS_RCU_TRACE */
+#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
}
/* Turn off heavyweight RCU tasks trace readers on idle/user exit. */
static void rcu_dynticks_task_trace_exit(void)
{
-#ifdef CONFIG_TASKS_RCU_TRACE
+#ifdef CONFIG_TASKS_TRACE_RCU
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
current->trc_reader_special.b.need_mb = false;
-#endif /* #ifdef CONFIG_TASKS_RCU_TRACE */
+#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
}
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 6c76988c..677ee3d 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -7,6 +7,8 @@
* Author: Paul E. McKenney <paulmck@linux.ibm.com>
*/
+#include <linux/kvm_para.h>
+
//////////////////////////////////////////////////////////////////////////////
//
// Controlling CPU stall warnings, including delay calculation.
@@ -117,17 +119,14 @@
}
/**
- * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
- *
- * Set the stall-warning timeout way off into the future, thus preventing
- * any RCU CPU stall-warning messages from appearing in the current set of
- * RCU grace periods.
+ * rcu_cpu_stall_reset - restart stall-warning timeout for current grace period
*
* The caller must disable hard irqs.
*/
void rcu_cpu_stall_reset(void)
{
- WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2);
+ WRITE_ONCE(rcu_state.jiffies_stall,
+ jiffies + rcu_jiffies_till_stall_check());
}
//////////////////////////////////////////////////////////////////////////////
@@ -267,8 +266,10 @@
struct task_struct *ts[8];
lockdep_assert_irqs_disabled();
- if (!rcu_preempt_blocked_readers_cgp(rnp))
+ if (!rcu_preempt_blocked_readers_cgp(rnp)) {
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return 0;
+ }
pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
rnp->level, rnp->grplo, rnp->grphi);
t = list_entry(rnp->gp_tasks->prev,
@@ -280,8 +281,8 @@
break;
}
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
- for (i--; i; i--) {
- t = ts[i];
+ while (i) {
+ t = ts[--i];
if (!try_invoke_on_locked_down_task(t, check_slow_task, &rscr))
pr_cont(" P%d", t->pid);
else
@@ -350,7 +351,7 @@
static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
{
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
rdp->last_accelerate & 0xffff, jiffies & 0xffff,
@@ -464,9 +465,10 @@
pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x ->cpu=%d\n",
rcu_state.name, j,
(long)rcu_seq_current(&rcu_state.gp_seq),
- data_race(rcu_state.gp_flags),
- gp_state_getname(rcu_state.gp_state), rcu_state.gp_state,
- gpk ? gpk->__state : ~0, cpu);
+ data_race(READ_ONCE(rcu_state.gp_flags)),
+ gp_state_getname(rcu_state.gp_state),
+ data_race(READ_ONCE(rcu_state.gp_state)),
+ gpk ? data_race(READ_ONCE(gpk->__state)) : ~0, cpu);
if (gpk) {
pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name);
pr_err("RCU grace-period kthread stack dump:\n");
@@ -509,7 +511,7 @@
(long)rcu_seq_current(&rcu_state.gp_seq),
data_race(rcu_state.gp_flags),
gp_state_getname(RCU_GP_WAIT_FQS), RCU_GP_WAIT_FQS,
- gpk->__state);
+ data_race(READ_ONCE(gpk->__state)));
pr_err("\tPossible timer handling issue on cpu=%d timer-softirq=%u\n",
cpu, kstat_softirqs_cpu(TIMER_SOFTIRQ, cpu));
}
@@ -568,11 +570,11 @@
pr_err("INFO: Stall ended before state dump start\n");
} else {
j = jiffies;
- gpa = data_race(rcu_state.gp_activity);
+ gpa = data_race(READ_ONCE(rcu_state.gp_activity));
pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n",
rcu_state.name, j - gpa, j, gpa,
- data_race(jiffies_till_next_fqs),
- rcu_get_root()->qsmask);
+ data_race(READ_ONCE(jiffies_till_next_fqs)),
+ data_race(READ_ONCE(rcu_get_root()->qsmask)));
}
}
/* Rewrite if needed in case of slow consoles. */
@@ -646,6 +648,7 @@
static void check_cpu_stall(struct rcu_data *rdp)
{
+ bool didstall = false;
unsigned long gs1;
unsigned long gs2;
unsigned long gps;
@@ -691,24 +694,46 @@
ULONG_CMP_GE(gps, js))
return; /* No stall or GP completed since entering function. */
rnp = rdp->mynode;
- jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
+ jn = jiffies + ULONG_MAX / 2;
if (rcu_gp_in_progress() &&
(READ_ONCE(rnp->qsmask) & rdp->grpmask) &&
cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
+ /*
+ * If a virtual machine is stopped by the host it can look to
+ * the watchdog like an RCU stall. Check to see if the host
+ * stopped the vm.
+ */
+ if (kvm_check_and_clear_guest_paused())
+ return;
+
/* We haven't checked in, so go dump stack. */
print_cpu_stall(gps);
if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
rcu_ftrace_dump(DUMP_ALL);
+ didstall = true;
} else if (rcu_gp_in_progress() &&
ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
+ /*
+ * If a virtual machine is stopped by the host it can look to
+ * the watchdog like an RCU stall. Check to see if the host
+ * stopped the vm.
+ */
+ if (kvm_check_and_clear_guest_paused())
+ return;
+
/* They had a few time units to dump stack, so complain. */
print_other_cpu_stall(gs2, gps);
if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
rcu_ftrace_dump(DUMP_ALL);
+ didstall = true;
+ }
+ if (didstall && READ_ONCE(rcu_state.jiffies_stall) == jn) {
+ jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
+ WRITE_ONCE(rcu_state.jiffies_stall, jn);
}
}
@@ -742,7 +767,7 @@
rcu_for_each_leaf_node(rnp) {
if (!cpup) {
- if (READ_ONCE(rnp->qsmask)) {
+ if (data_race(READ_ONCE(rnp->qsmask))) {
return false;
} else {
if (READ_ONCE(rnp->gp_tasks))
@@ -791,32 +816,34 @@
struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);
j = jiffies;
- ja = j - data_race(rcu_state.gp_activity);
- jr = j - data_race(rcu_state.gp_req_activity);
- js = j - data_race(rcu_state.gp_start);
- jw = j - data_race(rcu_state.gp_wake_time);
+ ja = j - data_race(READ_ONCE(rcu_state.gp_activity));
+ jr = j - data_race(READ_ONCE(rcu_state.gp_req_activity));
+ js = j - data_race(READ_ONCE(rcu_state.gp_start));
+ jw = j - data_race(READ_ONCE(rcu_state.gp_wake_time));
pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
rcu_state.name, gp_state_getname(rcu_state.gp_state),
- rcu_state.gp_state, t ? t->__state : 0x1ffff, t ? t->rt_priority : 0xffU,
- js, ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq),
- (long)data_race(rcu_state.gp_seq),
- (long)data_race(rcu_get_root()->gp_seq_needed),
- data_race(rcu_state.gp_max),
- data_race(rcu_state.gp_flags));
+ data_race(READ_ONCE(rcu_state.gp_state)),
+ t ? data_race(READ_ONCE(t->__state)) : 0x1ffff, t ? t->rt_priority : 0xffU,
+ js, ja, jr, jw, (long)data_race(READ_ONCE(rcu_state.gp_wake_seq)),
+ (long)data_race(READ_ONCE(rcu_state.gp_seq)),
+ (long)data_race(READ_ONCE(rcu_get_root()->gp_seq_needed)),
+ data_race(READ_ONCE(rcu_state.gp_max)),
+ data_race(READ_ONCE(rcu_state.gp_flags)));
rcu_for_each_node_breadth_first(rnp) {
if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) &&
- !data_race(rnp->qsmask) && !data_race(rnp->boost_tasks) &&
- !data_race(rnp->exp_tasks) && !data_race(rnp->gp_tasks))
+ !data_race(READ_ONCE(rnp->qsmask)) && !data_race(READ_ONCE(rnp->boost_tasks)) &&
+ !data_race(READ_ONCE(rnp->exp_tasks)) && !data_race(READ_ONCE(rnp->gp_tasks)))
continue;
pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n",
rnp->grplo, rnp->grphi,
- (long)data_race(rnp->gp_seq), (long)data_race(rnp->gp_seq_needed),
- data_race(rnp->qsmask),
- ".b"[!!data_race(rnp->boost_kthread_task)],
- ".B"[!!data_race(rnp->boost_tasks)],
- ".E"[!!data_race(rnp->exp_tasks)],
- ".G"[!!data_race(rnp->gp_tasks)],
- data_race(rnp->n_boosts));
+ (long)data_race(READ_ONCE(rnp->gp_seq)),
+ (long)data_race(READ_ONCE(rnp->gp_seq_needed)),
+ data_race(READ_ONCE(rnp->qsmask)),
+ ".b"[!!data_race(READ_ONCE(rnp->boost_kthread_task))],
+ ".B"[!!data_race(READ_ONCE(rnp->boost_tasks))],
+ ".E"[!!data_race(READ_ONCE(rnp->exp_tasks))],
+ ".G"[!!data_race(READ_ONCE(rnp->gp_tasks))],
+ data_race(READ_ONCE(rnp->n_boosts)));
if (!rcu_is_leaf_node(rnp))
continue;
for_each_leaf_node_possible_cpu(rnp, cpu) {
@@ -826,12 +853,12 @@
READ_ONCE(rdp->gp_seq_needed)))
continue;
pr_info("\tcpu %d ->gp_seq_needed %ld\n",
- cpu, (long)data_race(rdp->gp_seq_needed));
+ cpu, (long)data_race(READ_ONCE(rdp->gp_seq_needed)));
}
}
for_each_possible_cpu(cpu) {
rdp = per_cpu_ptr(&rcu_data, cpu);
- cbs += data_race(rdp->n_cbs_invoked);
+ cbs += data_race(READ_ONCE(rdp->n_cbs_invoked));
if (rcu_segcblist_is_offloaded(&rdp->cblist))
show_rcu_nocb_state(rdp);
}
@@ -913,11 +940,11 @@
if (rcu_gp_in_progress()) {
pr_info("%s: GP age %lu jiffies\n",
- __func__, jiffies - rcu_state.gp_start);
+ __func__, jiffies - data_race(READ_ONCE(rcu_state.gp_start)));
show_rcu_gp_kthreads();
} else {
pr_info("%s: Last GP end %lu jiffies ago\n",
- __func__, jiffies - rcu_state.gp_end);
+ __func__, jiffies - data_race(READ_ONCE(rcu_state.gp_end)));
preempt_disable();
rdp = this_cpu_ptr(&rcu_data);
rcu_check_gp_start_stall(rdp->mynode, rdp, j);
diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 29e8fc5..64a0828 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -64,6 +64,7 @@
torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
torture_param(int, weight_resched, -1, "Testing weight for resched_cpu() operations.");
torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
+torture_param(int, weight_single_rpc, -1, "Testing weight for single-CPU RPC operations.");
torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
torture_param(int, weight_many_wait, -1, "Testing weight for multi-CPU operations.");
@@ -86,6 +87,8 @@
long long n_resched;
long long n_single;
long long n_single_ofl;
+ long long n_single_rpc;
+ long long n_single_rpc_ofl;
long long n_single_wait;
long long n_single_wait_ofl;
long long n_many;
@@ -101,14 +104,17 @@
// Data for random primitive selection
#define SCF_PRIM_RESCHED 0
#define SCF_PRIM_SINGLE 1
-#define SCF_PRIM_MANY 2
-#define SCF_PRIM_ALL 3
-#define SCF_NPRIMS 7 // Need wait and no-wait versions of each,
- // except for SCF_PRIM_RESCHED.
+#define SCF_PRIM_SINGLE_RPC 2
+#define SCF_PRIM_MANY 3
+#define SCF_PRIM_ALL 4
+#define SCF_NPRIMS 8 // Need wait and no-wait versions of each,
+ // except for SCF_PRIM_RESCHED and
+ // SCF_PRIM_SINGLE_RPC.
static char *scf_prim_name[] = {
"resched_cpu",
"smp_call_function_single",
+ "smp_call_function_single_rpc",
"smp_call_function_many",
"smp_call_function",
};
@@ -128,6 +134,8 @@
bool scfc_out;
int scfc_cpu; // -1 for not _single().
bool scfc_wait;
+ bool scfc_rpc;
+ struct completion scfc_completion;
};
// Use to wait for all threads to start.
@@ -158,6 +166,7 @@
scfs.n_resched += scf_stats_p[i].n_resched;
scfs.n_single += scf_stats_p[i].n_single;
scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
+ scfs.n_single_rpc += scf_stats_p[i].n_single_rpc;
scfs.n_single_wait += scf_stats_p[i].n_single_wait;
scfs.n_single_wait_ofl += scf_stats_p[i].n_single_wait_ofl;
scfs.n_many += scf_stats_p[i].n_many;
@@ -168,9 +177,10 @@
if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
bangstr = "!!! ";
- pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
+ pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld single_rpc: %lld single_rpc_ofl: %lld many: %lld/%lld all: %lld/%lld ",
SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
+ scfs.n_single_rpc, scfs.n_single_rpc_ofl,
scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
torture_onoff_stats();
pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d\n", atomic_read(&n_errs),
@@ -282,10 +292,13 @@
out:
if (unlikely(!scfcp))
return;
- if (scfcp->scfc_wait)
+ if (scfcp->scfc_wait) {
WRITE_ONCE(scfcp->scfc_out, true);
- else
+ if (scfcp->scfc_rpc)
+ complete(&scfcp->scfc_completion);
+ } else {
kfree(scfcp);
+ }
}
// As above, but check for correct CPU.
@@ -319,6 +332,7 @@
scfcp->scfc_cpu = -1;
scfcp->scfc_wait = scfsp->scfs_wait;
scfcp->scfc_out = false;
+ scfcp->scfc_rpc = false;
}
}
switch (scfsp->scfs_prim) {
@@ -350,6 +364,34 @@
scfcp = NULL;
}
break;
+ case SCF_PRIM_SINGLE_RPC:
+ if (!scfcp)
+ break;
+ cpu = torture_random(trsp) % nr_cpu_ids;
+ scfp->n_single_rpc++;
+ scfcp->scfc_cpu = cpu;
+ scfcp->scfc_wait = true;
+ init_completion(&scfcp->scfc_completion);
+ scfcp->scfc_rpc = true;
+ barrier(); // Prevent race-reduction compiler optimizations.
+ scfcp->scfc_in = true;
+ ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, 0);
+ if (!ret) {
+ if (use_cpus_read_lock)
+ cpus_read_unlock();
+ else
+ preempt_enable();
+ wait_for_completion(&scfcp->scfc_completion);
+ if (use_cpus_read_lock)
+ cpus_read_lock();
+ else
+ preempt_disable();
+ } else {
+ scfp->n_single_rpc_ofl++;
+ kfree(scfcp);
+ scfcp = NULL;
+ }
+ break;
case SCF_PRIM_MANY:
if (scfsp->scfs_wait)
scfp->n_many_wait++;
@@ -379,10 +421,12 @@
}
if (scfcp && scfsp->scfs_wait) {
if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
- !scfcp->scfc_out))
+ !scfcp->scfc_out)) {
+ pr_warn("%s: Memory-ordering failure, scfs_prim: %d.\n", __func__, scfsp->scfs_prim);
atomic_inc(&n_mb_out_errs); // Leak rather than trash!
- else
+ } else {
kfree(scfcp);
+ }
barrier(); // Prevent race-reduction compiler optimizations.
}
if (use_cpus_read_lock)
@@ -453,8 +497,8 @@
scftorture_print_module_parms(const char *tag)
{
pr_alert(SCFTORT_FLAG
- "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
- verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
+ "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_rpc=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
+ verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_rpc, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
}
static void scf_cleanup_handler(void *unused)
@@ -469,7 +513,7 @@
return;
WRITE_ONCE(scfdone, true);
- if (nthreads)
+ if (nthreads && scf_stats_p)
for (i = 0; i < nthreads; i++)
torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
else
@@ -497,6 +541,7 @@
int firsterr = 0;
unsigned long weight_resched1 = weight_resched;
unsigned long weight_single1 = weight_single;
+ unsigned long weight_single_rpc1 = weight_single_rpc;
unsigned long weight_single_wait1 = weight_single_wait;
unsigned long weight_many1 = weight_many;
unsigned long weight_many_wait1 = weight_many_wait;
@@ -508,11 +553,13 @@
scftorture_print_module_parms("Start of test");
- if (weight_resched == -1 && weight_single == -1 && weight_single_wait == -1 &&
+ if (weight_resched == -1 &&
+ weight_single == -1 && weight_single_rpc == -1 && weight_single_wait == -1 &&
weight_many == -1 && weight_many_wait == -1 &&
weight_all == -1 && weight_all_wait == -1) {
weight_resched1 = 2 * nr_cpu_ids;
weight_single1 = 2 * nr_cpu_ids;
+ weight_single_rpc1 = 2 * nr_cpu_ids;
weight_single_wait1 = 2 * nr_cpu_ids;
weight_many1 = 2;
weight_many_wait1 = 2;
@@ -523,6 +570,8 @@
weight_resched1 = 0;
if (weight_single == -1)
weight_single1 = 0;
+ if (weight_single_rpc == -1)
+ weight_single_rpc1 = 0;
if (weight_single_wait == -1)
weight_single_wait1 = 0;
if (weight_many == -1)
@@ -534,7 +583,7 @@
if (weight_all_wait == -1)
weight_all_wait1 = 0;
}
- if (weight_single1 == 0 && weight_single_wait1 == 0 &&
+ if (weight_single1 == 0 && weight_single_rpc1 == 0 && weight_single_wait1 == 0 &&
weight_many1 == 0 && weight_many_wait1 == 0 &&
weight_all1 == 0 && weight_all_wait1 == 0) {
VERBOSE_SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
@@ -546,6 +595,7 @@
else if (weight_resched1)
VERBOSE_SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
+ scf_sel_add(weight_single_rpc1, SCF_PRIM_SINGLE_RPC, true);
scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2d9ff40f4..6a03c3f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7781,6 +7781,17 @@
preempt_schedule_common();
return 1;
}
+ /*
+ * In preemptible kernels, ->rcu_read_lock_nesting tells the tick
+ * whether the current CPU is in an RCU read-side critical section,
+ * so the tick can report quiescent states even for CPUs looping
+ * in kernel context. In contrast, in non-preemptible kernels,
+ * RCU readers leave no in-memory hints, which means that CPU-bound
+ * processes executing in kernel context might never report an
+ * RCU quiescent state. Therefore, the following code causes
+ * cond_resched() to report a quiescent state, but only when RCU
+ * is in urgent need of one.
+ */
#ifndef CONFIG_PREEMPT_RCU
rcu_all_qs();
#endif
diff --git a/kernel/torture.c b/kernel/torture.c
index 0a315c3..bb8f411 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -521,11 +521,11 @@
struct shuffle_task *stp;
cpumask_setall(shuffle_tmp_mask);
- get_online_cpus();
+ cpus_read_lock();
/* No point in shuffling if there is only one online CPU (ex: UP) */
if (num_online_cpus() == 1) {
- put_online_cpus();
+ cpus_read_unlock();
return;
}
@@ -541,7 +541,7 @@
set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
mutex_unlock(&shuffle_task_mutex);
- put_online_cpus();
+ cpus_read_unlock();
}
/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h
index 8b7a983..3430667 100644
--- a/tools/include/nolibc/nolibc.h
+++ b/tools/include/nolibc/nolibc.h
@@ -1031,7 +1031,7 @@
* scall32-o32.S in the kernel sources.
* - the system call is performed by calling "syscall"
* - syscall return comes in v0, and register a3 needs to be checked to know
- * if an error occured, in which case errno is in v0.
+ * if an error occurred, in which case errno is in v0.
* - the arguments are cast to long and assigned into the target registers
* which are then simply passed as registers to the asm code, so that we
* don't have to experience issues with register constraints.
@@ -2244,6 +2244,19 @@
}
static __attribute__((unused))
+int msleep(unsigned int msecs)
+{
+ struct timeval my_timeval = { msecs / 1000, (msecs % 1000) * 1000 };
+
+ if (sys_select(0, 0, 0, 0, &my_timeval) < 0)
+ return (my_timeval.tv_sec * 1000) +
+ (my_timeval.tv_usec / 1000) +
+ !!(my_timeval.tv_usec % 1000);
+ else
+ return 0;
+}
+
+static __attribute__((unused))
int stat(const char *path, struct stat *buf)
{
int ret = sys_stat(path, buf);
diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 15d937b..fd1ffaa 100755
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -68,16 +68,12 @@
cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
srand(n + me + systime());
ncpus = split(cpus, ca);
- curcpu = ca[int(rand() * ncpus + 1)];
- z = "";
- for (i = 1; 4 * i <= curcpu; i++)
- z = z "0";
- print "0x" 2 ^ (curcpu % 4) z;
+ print ca[int(rand() * ncpus + 1)];
}' < /dev/null`
n=$(($n+1))
- if ! taskset -p $cpumask $$ > /dev/null 2>&1
+ if ! taskset -c -p $cpumask $$ > /dev/null 2>&1
then
- echo taskset failure: '"taskset -p ' $cpumask $$ '"'
+ echo taskset failure: '"taskset -c -p ' $cpumask $$ '"'
exit 1
fi
diff --git a/tools/testing/selftests/rcutorture/bin/kcsan-collapse.sh b/tools/testing/selftests/rcutorture/bin/kcsan-collapse.sh
index e5cc6b2..1af5d6b 100755
--- a/tools/testing/selftests/rcutorture/bin/kcsan-collapse.sh
+++ b/tools/testing/selftests/rcutorture/bin/kcsan-collapse.sh
@@ -14,7 +14,7 @@
then
exit 0
fi
-cat $1/*/console.log |
+find $1 -name console.log -exec cat {} \; |
grep "BUG: KCSAN: " |
sed -e 's/^\[[^]]*] //' |
sort |
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-again.sh b/tools/testing/selftests/rcutorture/bin/kvm-again.sh
index d8c8483..5a0023d 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-again.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-again.sh
@@ -142,7 +142,7 @@
echo "Cannot copy from $oldrun to $rundir."
usage
fi
-rm -f "$rundir"/*/{console.log,console.log.diags,qemu_pid,qemu-retval,Warnings,kvm-test-1-run.sh.out,kvm-test-1-run-qemu.sh.out,vmlinux} "$rundir"/log
+rm -f "$rundir"/*/{console.log,console.log.diags,qemu_pid,qemu-pid,qemu-retval,Warnings,kvm-test-1-run.sh.out,kvm-test-1-run-qemu.sh.out,vmlinux} "$rundir"/log
touch "$rundir/log"
echo $scriptname $args | tee -a "$rundir/log"
echo $oldrun > "$rundir/re-run"
@@ -179,6 +179,6 @@
then
echo ---- Dryrun complete, directory: $rundir | tee -a "$rundir/log"
else
- ( cd "$rundir"; sh $T/runbatches.sh )
+ ( cd "$rundir"; sh $T/runbatches.sh ) | tee -a "$rundir/log"
kvm-end-run-stats.sh "$rundir" "$starttime"
fi
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-assign-cpus.sh b/tools/testing/selftests/rcutorture/bin/kvm-assign-cpus.sh
new file mode 100755
index 0000000..f99b2c1
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/kvm-assign-cpus.sh
@@ -0,0 +1,106 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Produce awk statements roughly depicting the system's CPU and cache
+# layout. If the required information is not available, produce
+# error messages as awk comments. Successful exit regardless.
+#
+# Usage: kvm-assign-cpus.sh /path/to/sysfs
+
+T=/tmp/kvm-assign-cpus.sh.$$
+trap 'rm -rf $T' 0 2
+mkdir $T
+
+sysfsdir=${1-/sys/devices/system/node}
+if ! cd "$sysfsdir" > $T/msg 2>&1
+then
+ sed -e 's/^/# /' < $T/msg
+ exit 0
+fi
+nodelist="`ls -d node*`"
+for i in node*
+do
+ if ! test -d $i/
+ then
+ echo "# Not a directory: $sysfsdir/node*"
+ exit 0
+ fi
+ for j in $i/cpu*/cache/index*
+ do
+ if ! test -d $j/
+ then
+ echo "# Not a directory: $sysfsdir/$j"
+ exit 0
+ else
+ break
+ fi
+ done
+ indexlist="`ls -d $i/cpu* | grep 'cpu[0-9][0-9]*' | head -1 | sed -e 's,^.*$,ls -d &/cache/index*,' | sh | sed -e 's,^.*/,,'`"
+ break
+done
+for i in node*/cpu*/cache/index*/shared_cpu_list
+do
+ if ! test -f $i
+ then
+ echo "# Not a file: $sysfsdir/$i"
+ exit 0
+ else
+ break
+ fi
+done
+firstshared=
+for i in $indexlist
+do
+ rm -f $T/cpulist
+ for n in node*
+ do
+ f="$n/cpu*/cache/$i/shared_cpu_list"
+ if ! cat $f > $T/msg 2>&1
+ then
+ sed -e 's/^/# /' < $T/msg
+ exit 0
+ fi
+ cat $f >> $T/cpulist
+ done
+ if grep -q '[-,]' $T/cpulist
+ then
+ if test -z "$firstshared"
+ then
+ firstshared="$i"
+ fi
+ fi
+done
+if test -z "$firstshared"
+then
+ splitindex="`echo $indexlist | sed -e 's/ .*$//'`"
+else
+ splitindex="$firstshared"
+fi
+nodenum=0
+for n in node*
+do
+ cat $n/cpu*/cache/$splitindex/shared_cpu_list | sort -u -k1n |
+ awk -v nodenum="$nodenum" '
+ BEGIN {
+ idx = 0;
+ }
+
+ {
+ nlists = split($0, cpulists, ",");
+ for (i = 1; i <= nlists; i++) {
+ listsize = split(cpulists[i], cpus, "-");
+ if (listsize == 1)
+ cpus[2] = cpus[1];
+ for (j = cpus[1]; j <= cpus[2]; j++) {
+ print "cpu[" nodenum "][" idx "] = " j ";";
+ idx++;
+ }
+ }
+ }
+
+ END {
+ print "nodecpus[" nodenum "] = " idx ";";
+ }'
+ nodenum=`expr $nodenum + 1`
+done
+echo "numnodes = $nodenum;"
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-get-cpus-script.sh b/tools/testing/selftests/rcutorture/bin/kvm-get-cpus-script.sh
new file mode 100755
index 0000000..20c7c53
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/kvm-get-cpus-script.sh
@@ -0,0 +1,88 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Create an awk script that takes as input numbers of CPUs and outputs
+# lists of CPUs, one per line in both cases.
+#
+# Usage: kvm-get-cpus-script.sh /path/to/cpu/arrays /path/to/put/script [ /path/to/state ]
+#
+# The CPU arrays are output by kvm-assign-cpus.sh, and are valid awk
+# statements initializing the variables describing the system's topology.
+#
+# The optional state is input by this script (if the file exists and is
+# non-empty), and can also be output by this script.
+
+cpuarrays="${1-/sys/devices/system/node}"
+scriptfile="${2}"
+statefile="${3}"
+
+if ! test -f "$cpuarrays"
+then
+ echo "File not found: $cpuarrays" 1>&2
+ exit 1
+fi
+scriptdir="`dirname "$scriptfile"`"
+if ! test -d "$scriptdir" || ! test -x "$scriptdir" || ! test -w "$scriptdir"
+then
+ echo "Directory not usable for script output: $scriptdir"
+ exit 1
+fi
+
+cat << '___EOF___' > "$scriptfile"
+BEGIN {
+___EOF___
+cat "$cpuarrays" >> "$scriptfile"
+if test -r "$statefile"
+then
+ cat "$statefile" >> "$scriptfile"
+fi
+cat << '___EOF___' >> "$scriptfile"
+}
+
+# Do we have the system architecture to guide CPU affinity?
+function gotcpus()
+{
+ return numnodes != "";
+}
+
+# Return a comma-separated list of the next n CPUs.
+function nextcpus(n, i, s)
+{
+ for (i = 0; i < n; i++) {
+ if (nodecpus[curnode] == "")
+ curnode = 0;
+ if (cpu[curnode][curcpu[curnode]] == "")
+ curcpu[curnode] = 0;
+ if (s != "")
+ s = s ",";
+ s = s cpu[curnode][curcpu[curnode]];
+ curcpu[curnode]++;
+ curnode++
+ }
+ return s;
+}
+
+# Dump out the current node/CPU state so that a later invocation of this
+# script can continue where this one left off. Of course, this only works
+# when a state file was specified and where there was valid sysfs state.
+# Returns 1 if the state was dumped, 0 otherwise.
+#
+# Dumping the state for one system configuration and loading it into
+# another isn't likely to do what you want, whatever that might be.
+function dumpcpustate( i, fn)
+{
+___EOF___
+echo ' fn = "'"$statefile"'";' >> $scriptfile
+cat << '___EOF___' >> "$scriptfile"
+ if (fn != "" && gotcpus()) {
+ print "curnode = " curnode ";" > fn;
+ for (i = 0; i < numnodes; i++)
+ if (curcpu[i] != "")
+ print "curcpu[" i "] = " curcpu[i] ";" >> fn;
+ return 1;
+ }
+ if (fn != "")
+ print "# No CPU state to dump." > fn;
+ return 0;
+}
+___EOF___
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck-lock.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck-lock.sh
index f3a7a5e..db2c0e2 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck-lock.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck-lock.sh
@@ -25,7 +25,7 @@
echo "$configfile -------"
else
title="$configfile ------- $ncs acquisitions/releases"
- dur=`sed -e 's/^.* locktorture.shutdown_secs=//' -e 's/ .*$//' < $i/qemu-cmd 2> /dev/null`
+ dur=`grep -v '^#' $i/qemu-cmd | sed -e 's/^.* locktorture.shutdown_secs=//' -e 's/ .*$//' 2> /dev/null`
if test -z "$dur"
then
:
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck-scf.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck-scf.sh
index 671bfee..3afa5c6 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck-scf.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck-scf.sh
@@ -25,7 +25,7 @@
then
echo "$configfile ------- "
else
- dur="`sed -e 's/^.* scftorture.shutdown_secs=//' -e 's/ .*$//' < $i/qemu-cmd 2> /dev/null`"
+ dur="`grep -v '^#' $i/qemu-cmd | sed -e 's/^.* scftorture.shutdown_secs=//' -e 's/ .*$//' 2> /dev/null`"
if test -z "$dur"
then
rate=""
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
index e01b31b..0a54199 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
@@ -74,7 +74,10 @@
done
if test -f "$rd/kcsan.sum"
then
- if grep -q CONFIG_KCSAN=y $T
+ if ! test -f $T
+ then
+ :
+ elif grep -q CONFIG_KCSAN=y $T
then
echo "Compiler or architecture does not support KCSAN!"
echo Did you forget to switch your compiler with '--kmake-arg CC=<cc-that-supports-kcsan>'?
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-remote-noreap.sh b/tools/testing/selftests/rcutorture/bin/kvm-remote-noreap.sh
new file mode 100755
index 0000000..014ce68
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/kvm-remote-noreap.sh
@@ -0,0 +1,30 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Periodically scan a directory tree to prevent files from being reaped
+# by systemd and friends on long runs.
+#
+# Usage: kvm-remote-noreap.sh pathname
+#
+# Copyright (C) 2021 Facebook, Inc.
+#
+# Authors: Paul E. McKenney <paulmck@kernel.org>
+
+pathname="$1"
+if test "$pathname" = ""
+then
+ echo Usage: kvm-remote-noreap.sh pathname
+ exit 1
+fi
+if ! test -d "$pathname"
+then
+ echo Usage: kvm-remote-noreap.sh pathname
+ echo " pathname must be a directory."
+ exit 2
+fi
+
+while test -d "$pathname"
+do
+ find "$pathname" -type f -exec touch -c {} \; > /dev/null 2>&1
+ sleep 30
+done
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-remote.sh b/tools/testing/selftests/rcutorture/bin/kvm-remote.sh
index 79e680e..03126eb 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-remote.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-remote.sh
@@ -124,10 +124,12 @@
n = $1;
sub(/\./, "", n);
fn = dest "/kvm-remote-" n ".sh"
+ print "kvm-remote-noreap.sh " rundir " &" > fn;
scenarios = "";
for (i = 2; i <= NF; i++)
scenarios = scenarios " " $i;
- print "kvm-test-1-run-batch.sh" scenarios > fn;
+ print "kvm-test-1-run-batch.sh" scenarios >> fn;
+ print "sync" >> fn;
print "rm " rundir "/remote.run" >> fn;
}'
chmod +x $T/bin/kvm-remote-*.sh
@@ -172,11 +174,20 @@
do
ssh $1 "test -f \"$2\""
ret=$?
- if test "$ret" -ne 255
+ if test "$ret" -eq 255
then
+ echo " ---" ssh failure to $1 checking for file $2, retry after $sleeptime seconds. `date`
+ elif test "$ret" -eq 0
+ then
+ return 0
+ elif test "$ret" -eq 1
+ then
+ echo " ---" File \"$2\" not found: ssh $1 test -f \"$2\"
+ return 1
+ else
+ echo " ---" Exit code $ret: ssh $1 test -f \"$2\", retry after $sleeptime seconds. `date`
return $ret
fi
- echo " ---" ssh failure to $1 checking for file $2, retry after $sleeptime seconds. `date`
sleep $sleeptime
done
}
@@ -242,7 +253,8 @@
do
sleep 30
done
- ( cd "$oldrun"; ssh $i "cd $rundir; tar -czf - kvm-remote-*.sh.out */console.log */kvm-test-1-run*.sh.out */qemu_pid */qemu-retval; rm -rf $T > /dev/null 2>&1" | tar -xzf - )
+ echo " ---" Collecting results from $i `date`
+ ( cd "$oldrun"; ssh $i "cd $rundir; tar -czf - kvm-remote-*.sh.out */console.log */kvm-test-1-run*.sh.out */qemu[_-]pid */qemu-retval */qemu-affinity; rm -rf $T > /dev/null 2>&1" | tar -xzf - )
done
( kvm-end-run-stats.sh "$oldrun" "$starttime"; echo $? > $T/exitcode ) | tee -a "$oldrun/remote-log"
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-batch.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-batch.sh
index 7ea0809e..1e29d65 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-batch.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-batch.sh
@@ -50,10 +50,34 @@
echo ---- System running test: `uname -a`
echo ---- Starting kernels. `date` | tee -a log
$TORTURE_JITTER_START
+kvm-assign-cpus.sh /sys/devices/system/node > $T/cpuarray.awk
for i in "$@"
do
echo ---- System running test: `uname -a` > $i/kvm-test-1-run-qemu.sh.out
echo > $i/kvm-test-1-run-qemu.sh.out
+ export TORTURE_AFFINITY=
+ kvm-get-cpus-script.sh $T/cpuarray.awk $T/cpubatches.awk $T/cpustate
+ cat << ' ___EOF___' >> $T/cpubatches.awk
+ END {
+ affinitylist = "";
+ if (!gotcpus()) {
+ print "echo No CPU-affinity information, so no taskset command.";
+ } else if (cpu_count !~ /^[0-9][0-9]*$/) {
+ print "echo " scenario ": Bogus number of CPUs (old qemu-cmd?), so no taskset command.";
+ } else {
+ affinitylist = nextcpus(cpu_count);
+ if (!(affinitylist ~ /^[0-9,-][0-9,-]*$/))
+ print "echo " scenario ": Bogus CPU-affinity information, so no taskset command.";
+ else if (!dumpcpustate())
+ print "echo " scenario ": Could not dump state, so no taskset command.";
+ else
+ print "export TORTURE_AFFINITY=" affinitylist;
+ }
+ }
+ ___EOF___
+ cpu_count="`grep '# TORTURE_CPU_COUNT=' $i/qemu-cmd | sed -e 's/^.*=//'`"
+ affinity_export="`awk -f $T/cpubatches.awk -v cpu_count="$cpu_count" -v scenario=$i < /dev/null`"
+ $affinity_export
kvm-test-1-run-qemu.sh $i >> $i/kvm-test-1-run-qemu.sh.out 2>&1 &
done
for i in $runfiles
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-qemu.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-qemu.sh
index 5b1aa2a..4428058 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-qemu.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run-qemu.sh
@@ -39,27 +39,34 @@
grep '^#' $resdir/qemu-cmd | sed -e 's/^# //' > $T/qemu-cmd-settings
. $T/qemu-cmd-settings
-# Decorate qemu-cmd with redirection, backgrounding, and PID capture
-sed -e 's/$/ 2>\&1 \&/' < $resdir/qemu-cmd > $T/qemu-cmd
-echo 'echo $! > $resdir/qemu_pid' >> $T/qemu-cmd
+# Decorate qemu-cmd with affinity, redirection, backgrounding, and PID capture
+taskset_command=
+if test -n "$TORTURE_AFFINITY"
+then
+ taskset_command="taskset -c $TORTURE_AFFINITY "
+fi
+sed -e 's/^[^#].*$/'"$taskset_command"'& 2>\&1 \&/' < $resdir/qemu-cmd > $T/qemu-cmd
+echo 'qemu_pid=$!' >> $T/qemu-cmd
+echo 'echo $qemu_pid > $resdir/qemu-pid' >> $T/qemu-cmd
+echo 'taskset -c -p $qemu_pid > $resdir/qemu-affinity' >> $T/qemu-cmd
# In case qemu refuses to run...
echo "NOTE: $QEMU either did not run or was interactive" > $resdir/console.log
# Attempt to run qemu
kstarttime=`gawk 'BEGIN { print systime() }' < /dev/null`
-( . $T/qemu-cmd; wait `cat $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
+( . $T/qemu-cmd; wait `cat $resdir/qemu-pid`; echo $? > $resdir/qemu-retval ) &
commandcompleted=0
if test -z "$TORTURE_KCONFIG_GDB_ARG"
then
sleep 10 # Give qemu's pid a chance to reach the file
- if test -s "$resdir/qemu_pid"
+ if test -s "$resdir/qemu-pid"
then
- qemu_pid=`cat "$resdir/qemu_pid"`
- echo Monitoring qemu job at pid $qemu_pid
+ qemu_pid=`cat "$resdir/qemu-pid"`
+ echo Monitoring qemu job at pid $qemu_pid `date`
else
qemu_pid=""
- echo Monitoring qemu job at yet-as-unknown pid
+ echo Monitoring qemu job at yet-as-unknown pid `date`
fi
fi
if test -n "$TORTURE_KCONFIG_GDB_ARG"
@@ -82,9 +89,9 @@
fi
while :
do
- if test -z "$qemu_pid" -a -s "$resdir/qemu_pid"
+ if test -z "$qemu_pid" && test -s "$resdir/qemu-pid"
then
- qemu_pid=`cat "$resdir/qemu_pid"`
+ qemu_pid=`cat "$resdir/qemu-pid"`
fi
kruntime=`gawk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
if test -z "$qemu_pid" || kill -0 "$qemu_pid" > /dev/null 2>&1
@@ -115,22 +122,22 @@
break
fi
done
-if test -z "$qemu_pid" -a -s "$resdir/qemu_pid"
+if test -z "$qemu_pid" && test -s "$resdir/qemu-pid"
then
- qemu_pid=`cat "$resdir/qemu_pid"`
+ qemu_pid=`cat "$resdir/qemu-pid"`
fi
-if test $commandcompleted -eq 0 -a -n "$qemu_pid"
+if test $commandcompleted -eq 0 && test -n "$qemu_pid"
then
if ! test -f "$resdir/../STOP.1"
then
- echo Grace period for qemu job at pid $qemu_pid
+ echo Grace period for qemu job at pid $qemu_pid `date`
fi
oldline="`tail $resdir/console.log`"
while :
do
if test -f "$resdir/../STOP.1"
then
- echo "PID $qemu_pid killed due to run STOP.1 request" >> $resdir/Warnings 2>&1
+ echo "PID $qemu_pid killed due to run STOP.1 request `date`" >> $resdir/Warnings 2>&1
kill -KILL $qemu_pid
break
fi
@@ -152,13 +159,17 @@
then
last_ts=0
fi
- if test "$newline" != "$oldline" -a "$last_ts" -lt $((seconds + $TORTURE_SHUTDOWN_GRACE))
+ if test "$newline" != "$oldline" && test "$last_ts" -lt $((seconds + $TORTURE_SHUTDOWN_GRACE)) && test "$last_ts" -gt "$TORTURE_SHUTDOWN_GRACE"
then
must_continue=yes
+ if test $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
+ then
+ echo Continuing at console.log time $last_ts \"`tail -n 1 $resdir/console.log`\" `date`
+ fi
fi
- if test $must_continue = no -a $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
+ if test $must_continue = no && test $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
then
- echo "!!! PID $qemu_pid hung at $kruntime vs. $seconds seconds" >> $resdir/Warnings 2>&1
+ echo "!!! PID $qemu_pid hung at $kruntime vs. $seconds seconds `date`" >> $resdir/Warnings 2>&1
kill -KILL $qemu_pid
break
fi
@@ -172,5 +183,3 @@
# Tell the script that this run is done.
rm -f $resdir/build.run
-
-parse-console.sh $resdir/console.log $title
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 420ed5c..f4c8055 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -205,6 +205,7 @@
echo "# TORTURE_JITTER_START=\"$TORTURE_JITTER_START\"" >> $resdir/qemu-cmd
echo "# TORTURE_JITTER_STOP=\"$TORTURE_JITTER_STOP\"" >> $resdir/qemu-cmd
echo "# TORTURE_TRUST_MAKE=\"$TORTURE_TRUST_MAKE\"; export TORTURE_TRUST_MAKE" >> $resdir/qemu-cmd
+echo "# TORTURE_CPU_COUNT=$cpu_count" >> $resdir/qemu-cmd
if test -n "$TORTURE_BUILDONLY"
then
@@ -214,3 +215,4 @@
fi
kvm-test-1-run-qemu.sh $resdir
+parse-console.sh $resdir/console.log $title
diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index b4ac4ee3..f442d84 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -430,17 +430,10 @@
git diff HEAD >> $resdir/$ds/testid.txt
fi
___EOF___
-awk < $T/cfgcpu.pack \
- -v TORTURE_BUILDONLY="$TORTURE_BUILDONLY" \
- -v CONFIGDIR="$CONFIGFRAG/" \
- -v KVM="$KVM" \
- -v ncpus=$cpus \
- -v jitter="$jitter" \
- -v rd=$resdir/$ds/ \
- -v dur=$dur \
- -v TORTURE_QEMU_ARG="$TORTURE_QEMU_ARG" \
- -v TORTURE_BOOTARGS="$TORTURE_BOOTARGS" \
-'BEGIN {
+kvm-assign-cpus.sh /sys/devices/system/node > $T/cpuarray.awk
+kvm-get-cpus-script.sh $T/cpuarray.awk $T/dumpbatches.awk
+cat << '___EOF___' >> $T/dumpbatches.awk
+BEGIN {
i = 0;
}
@@ -451,7 +444,7 @@
}
# Dump out the scripting required to run one test batch.
-function dump(first, pastlast, batchnum)
+function dump(first, pastlast, batchnum, affinitylist)
{
print "echo ----Start batch " batchnum ": `date` | tee -a " rd "log";
print "needqemurun="
@@ -483,6 +476,14 @@
print "echo ", cfr[jn], cpusr[jn] ovf ": Starting build. `date` | tee -a " rd "log";
print "mkdir " rd cfr[jn] " || :";
print "touch " builddir ".wait";
+ affinitylist = "";
+ if (gotcpus()) {
+ affinitylist = nextcpus(cpusr[jn]);
+ }
+ if (affinitylist ~ /^[0-9,-][0-9,-]*$/)
+ print "export TORTURE_AFFINITY=" affinitylist;
+ else
+ print "export TORTURE_AFFINITY=";
print "kvm-test-1-run.sh " CONFIGDIR cf[j], rd cfr[jn], dur " \"" TORTURE_QEMU_ARG "\" \"" TORTURE_BOOTARGS "\" > " rd cfr[jn] "/kvm-test-1-run.sh.out 2>&1 &"
print "echo ", cfr[jn], cpusr[jn] ovf ": Waiting for build to complete. `date` | tee -a " rd "log";
print "while test -f " builddir ".wait"
@@ -560,7 +561,19 @@
# Dump the last batch.
if (ncpus != 0)
dump(first, i, batchnum);
-}' >> $T/script
+}
+___EOF___
+awk < $T/cfgcpu.pack \
+ -v TORTURE_BUILDONLY="$TORTURE_BUILDONLY" \
+ -v CONFIGDIR="$CONFIGFRAG/" \
+ -v KVM="$KVM" \
+ -v ncpus=$cpus \
+ -v jitter="$jitter" \
+ -v rd=$resdir/$ds/ \
+ -v dur=$dur \
+ -v TORTURE_QEMU_ARG="$TORTURE_QEMU_ARG" \
+ -v TORTURE_BOOTARGS="$TORTURE_BOOTARGS" \
+ -f $T/dumpbatches.awk >> $T/script
echo kvm-end-run-stats.sh "$resdir/$ds" "$starttime" >> $T/script
# Extract the tests and their batches from the script.
diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh
index 53ec7c0..363f560 100755
--- a/tools/testing/selftests/rcutorture/bin/torture.sh
+++ b/tools/testing/selftests/rcutorture/bin/torture.sh
@@ -53,6 +53,7 @@
do_kvfree=yes
do_kasan=yes
do_kcsan=no
+do_clocksourcewd=yes
# doyesno - Helper function for yes/no arguments
function doyesno () {
@@ -72,6 +73,7 @@
echo " --configs-scftorture \"config-file list w/ repeat factor (2*CFLIST)\""
echo " --doall"
echo " --doallmodconfig / --do-no-allmodconfig"
+ echo " --do-clocksourcewd / --do-no-clocksourcewd"
echo " --do-kasan / --do-no-kasan"
echo " --do-kcsan / --do-no-kcsan"
echo " --do-kvfree / --do-no-kvfree"
@@ -109,7 +111,7 @@
configs_scftorture="$configs_scftorture $2"
shift
;;
- --doall)
+ --do-all|--doall)
do_allmodconfig=yes
do_rcutorture=yes
do_locktorture=yes
@@ -119,10 +121,14 @@
do_kvfree=yes
do_kasan=yes
do_kcsan=yes
+ do_clocksourcewd=yes
;;
--do-allmodconfig|--do-no-allmodconfig)
do_allmodconfig=`doyesno "$1" --do-allmodconfig`
;;
+ --do-clocksourcewd|--do-no-clocksourcewd)
+ do_clocksourcewd=`doyesno "$1" --do-clocksourcewd`
+ ;;
--do-kasan|--do-no-kasan)
do_kasan=`doyesno "$1" --do-kasan`
;;
@@ -135,7 +141,7 @@
--do-locktorture|--do-no-locktorture)
do_locktorture=`doyesno "$1" --do-locktorture`
;;
- --do-none)
+ --do-none|--donone)
do_allmodconfig=no
do_rcutorture=no
do_locktorture=no
@@ -145,6 +151,7 @@
do_kvfree=no
do_kasan=no
do_kcsan=no
+ do_clocksourcewd=no
;;
--do-rcuscale|--do-no-rcuscale)
do_rcuscale=`doyesno "$1" --do-rcuscale`
@@ -279,9 +286,9 @@
# torture_bootargs="[ kernel boot arguments ]"
# torture_set flavor [ kvm.sh arguments ]
#
-# Note that "flavor" is an arbitrary string. Supply --torture if needed.
-# Note that quoting is problematic. So on the command line, pass multiple
-# values with multiple kvm.sh argument instances.
+# Note that "flavor" is an arbitrary string that does not affect kvm.sh
+# in any way. So also supply --torture if you need something other than
+# the default.
function torture_set {
local cur_kcsan_kmake_args=
local kcsan_kmake_tag=
@@ -377,6 +384,22 @@
torture_set "rcuscale-kvfree" tools/testing/selftests/rcutorture/bin/kvm.sh --torture rcuscale --allcpus --duration 10 --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 1G --trust-make
fi
+if test "$do_clocksourcewd" = "yes"
+then
+ torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000"
+ torture_set "clocksourcewd-1" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --kconfig "CONFIG_TEST_CLOCKSOURCE_WATCHDOG=y" --trust-make
+
+ torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 clocksource.max_cswd_read_retries=1"
+ torture_set "clocksourcewd-2" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --kconfig "CONFIG_TEST_CLOCKSOURCE_WATCHDOG=y" --trust-make
+
+ # In case our work is already done...
+ if test "$do_rcutorture" != "yes"
+ then
+ torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000"
+ torture_set "clocksourcewd-3" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 45s --configs TREE03 --trust-make
+ fi
+fi
+
echo " --- " $scriptname $args
echo " --- " Done `date` | tee -a $T/log
ret=0
@@ -395,6 +418,10 @@
nfailures="`wc -l "$T/failures" | awk '{ print $1 }'`"
ret=2
fi
+if test "$do_kcsan" = "yes"
+then
+ TORTURE_KCONFIG_KCSAN_ARG=1 tools/testing/selftests/rcutorture/bin/kcsan-collapse.sh tools/testing/selftests/rcutorture/res/$ds > tools/testing/selftests/rcutorture/res/$ds/kcsan.sum
+fi
echo Started at $startdate, ended at `date`, duration `get_starttime_duration $starttime`. | tee -a $T/log
echo Summary: Successes: $nsuccesses Failures: $nfailures. | tee -a $T/log
tdir="`cat $T/successes $T/failures | head -1 | awk '{ print $NF }' | sed -e 's,/[^/]\+/*$,,'`"
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/RUDE01 b/tools/testing/selftests/rcutorture/configs/rcu/RUDE01
index bafe94c..3ca1124 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/RUDE01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/RUDE01
@@ -1,5 +1,5 @@
CONFIG_SMP=y
-CONFIG_NR_CPUS=2
+CONFIG_NR_CPUS=4
CONFIG_HOTPLUG_CPU=y
CONFIG_PREEMPT_NONE=n
CONFIG_PREEMPT_VOLUNTARY=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS01 b/tools/testing/selftests/rcutorture/configs/rcu/TASKS01
index bafe94c..3ca1124 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TASKS01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS01
@@ -1,5 +1,5 @@
CONFIG_SMP=y
-CONFIG_NR_CPUS=2
+CONFIG_NR_CPUS=4
CONFIG_HOTPLUG_CPU=y
CONFIG_PREEMPT_NONE=n
CONFIG_PREEMPT_VOLUNTARY=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03 b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03
index ea43990..dc02083 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03
@@ -1,5 +1,5 @@
CONFIG_SMP=y
-CONFIG_NR_CPUS=2
+CONFIG_NR_CPUS=4
CONFIG_PREEMPT_NONE=n
CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=y
