Merge branch 'rcu-tasks.2014.09.10a' into HEAD
rcu-tasks.2014.09.10a: Add RCU-tasks flavor of RCU.
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 68fe3ad..ef5a2fd 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -56,8 +56,20 @@
two jiffies. (This is a cpp macro, not a kernel configuration
parameter.)
-When a CPU detects that it is stalling, it will print a message similar
-to the following:
+rcupdate.rcu_task_stall_timeout
+
+ This boot/sysfs parameter controls the RCU-tasks stall warning
+ interval. A value of zero or less suppresses RCU-tasks stall
+ warnings. A positive value sets the stall-warning interval
+ in jiffies. An RCU-tasks stall warning starts wtih the line:
+
+ INFO: rcu_tasks detected stalls on tasks:
+
+ And continues with the output of sched_show_task() for each
+ task stalling the current RCU-tasks grace period.
+
+For non-RCU-tasks flavors of RCU, when a CPU detects that it is stalling,
+it will print a message similar to the following:
INFO: rcu_sched_state detected stall on CPU 5 (t=2500 jiffies)
@@ -174,8 +186,12 @@
o A CPU looping with bottom halves disabled. This condition can
result in RCU-sched and RCU-bh stalls.
-o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
- without invoking schedule().
+o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the
+ kernel without invoking schedule(). Note that cond_resched()
+ does not necessarily prevent RCU CPU stall warnings. Therefore,
+ if the looping in the kernel is really expected and desirable
+ behavior, you might need to replace some of the cond_resched()
+ calls with calls to cond_resched_rcu_qs().
o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
happen to preempt a low-priority task in the middle of an RCU
@@ -208,11 +224,10 @@
This resulted in a series of RCU CPU stall warnings, eventually
leading the realization that the CPU had failed.
-The RCU, RCU-sched, and RCU-bh implementations have CPU stall warning.
-SRCU does not have its own CPU stall warnings, but its calls to
-synchronize_sched() will result in RCU-sched detecting RCU-sched-related
-CPU stalls. Please note that RCU only detects CPU stalls when there is
-a grace period in progress. No grace period, no CPU stall warnings.
+The RCU, RCU-sched, RCU-bh, and RCU-tasks implementations have CPU stall
+warning. Note that SRCU does -not- have CPU stall warnings. Please note
+that RCU only detects CPU stalls when there is a grace period in progress.
+No grace period, no CPU stall warnings.
To diagnose the cause of the stall, inspect the stack traces.
The offending function will usually be near the top of the stack.
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 0a104be..e1147bc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3000,6 +3000,11 @@
rcupdate.rcu_cpu_stall_timeout= [KNL]
Set timeout for RCU CPU stall warning messages.
+ rcupdate.rcu_task_stall_timeout= [KNL]
+ Set timeout in jiffies for RCU task stall warning
+ messages. Disable with a value less than or equal
+ to zero.
+
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,
diff --git a/fs/file.c b/fs/file.c
index 66923fe..1cafc4c 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -367,7 +367,7 @@
struct file * file = xchg(&fdt->fd[i], NULL);
if (file) {
filp_close(file, files);
- cond_resched();
+ cond_resched_rcu_qs();
}
}
i++;
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 2bb4c4f3..77fc43f 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -111,12 +111,21 @@
#ifdef CONFIG_PREEMPT_RCU
#define INIT_TASK_RCU_PREEMPT(tsk) \
.rcu_read_lock_nesting = 0, \
- .rcu_read_unlock_special = 0, \
+ .rcu_read_unlock_special.s = 0, \
.rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), \
INIT_TASK_RCU_TREE_PREEMPT()
#else
#define INIT_TASK_RCU_PREEMPT(tsk)
#endif
+#ifdef CONFIG_TASKS_RCU
+#define INIT_TASK_RCU_TASKS(tsk) \
+ .rcu_tasks_holdout = false, \
+ .rcu_tasks_holdout_list = \
+ LIST_HEAD_INIT(tsk.rcu_tasks_holdout_list), \
+ .rcu_tasks_idle_cpu = -1,
+#else
+#define INIT_TASK_RCU_TASKS(tsk)
+#endif
extern struct cred init_cred;
@@ -224,6 +233,7 @@
INIT_FTRACE_GRAPH \
INIT_TRACE_RECURSION \
INIT_TASK_RCU_PREEMPT(tsk) \
+ INIT_TASK_RCU_TASKS(tsk) \
INIT_CPUSET_SEQ(tsk) \
INIT_RT_MUTEXES(tsk) \
INIT_VTIME(tsk) \
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 334ff89..5cafd60 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -55,6 +55,7 @@
RCU_FLAVOR,
RCU_BH_FLAVOR,
RCU_SCHED_FLAVOR,
+ RCU_TASKS_FLAVOR,
SRCU_FLAVOR,
INVALID_RCU_FLAVOR
};
@@ -197,6 +198,28 @@
void synchronize_sched(void);
+/**
+ * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual callback function to be invoked after the grace period
+ *
+ * The callback function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed. call_rcu_tasks() assumes
+ * that the read-side critical sections end at a voluntary context
+ * switch (not a preemption!), entry into idle, or transition to usermode
+ * execution. As such, there are no read-side primitives analogous to
+ * rcu_read_lock() and rcu_read_unlock() because this primitive is intended
+ * to determine that all tasks have passed through a safe state, not so
+ * much for data-strcuture synchronization.
+ *
+ * See the description of call_rcu() for more detailed information on
+ * memory ordering guarantees.
+ */
+void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head));
+void synchronize_rcu_tasks(void);
+void rcu_barrier_tasks(void);
+
#ifdef CONFIG_PREEMPT_RCU
void __rcu_read_lock(void);
@@ -238,8 +261,8 @@
/* Internal to kernel */
void rcu_init(void);
-void rcu_sched_qs(int cpu);
-void rcu_bh_qs(int cpu);
+void rcu_sched_qs(void);
+void rcu_bh_qs(void);
void rcu_check_callbacks(int cpu, int user);
struct notifier_block;
void rcu_idle_enter(void);
@@ -302,6 +325,36 @@
rcu_irq_exit(); \
} while (0)
+/*
+ * Note a voluntary context switch for RCU-tasks benefit. This is a
+ * macro rather than an inline function to avoid #include hell.
+ */
+#ifdef CONFIG_TASKS_RCU
+#define TASKS_RCU(x) x
+extern struct srcu_struct tasks_rcu_exit_srcu;
+#define rcu_note_voluntary_context_switch(t) \
+ do { \
+ if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \
+ ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \
+ } while (0)
+#else /* #ifdef CONFIG_TASKS_RCU */
+#define TASKS_RCU(x) do { } while (0)
+#define rcu_note_voluntary_context_switch(t) do { } while (0)
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
+/**
+ * cond_resched_rcu_qs - Report potential quiescent states to RCU
+ *
+ * This macro resembles cond_resched(), except that it is defined to
+ * report potential quiescent states to RCU-tasks even if the cond_resched()
+ * machinery were to be shut off, as some advocate for PREEMPT kernels.
+ */
+#define cond_resched_rcu_qs() \
+do { \
+ rcu_note_voluntary_context_switch(current); \
+ cond_resched(); \
+} while (0)
+
#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
bool __rcu_is_watching(void);
#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index d40a6a4..38cc5b1 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -80,7 +80,7 @@
static inline void rcu_note_context_switch(int cpu)
{
- rcu_sched_qs(cpu);
+ rcu_sched_qs();
}
/*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5c2c885..42888d7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1212,6 +1212,13 @@
struct hrtimer dl_timer;
};
+union rcu_special {
+ struct {
+ bool blocked;
+ bool need_qs;
+ } b;
+ short s;
+};
struct rcu_node;
enum perf_event_task_context {
@@ -1264,12 +1271,18 @@
#ifdef CONFIG_PREEMPT_RCU
int rcu_read_lock_nesting;
- char rcu_read_unlock_special;
+ union rcu_special rcu_read_unlock_special;
struct list_head rcu_node_entry;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TREE_PREEMPT_RCU
struct rcu_node *rcu_blocked_node;
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#ifdef CONFIG_TASKS_RCU
+ unsigned long rcu_tasks_nvcsw;
+ bool rcu_tasks_holdout;
+ struct list_head rcu_tasks_holdout_list;
+ int rcu_tasks_idle_cpu;
+#endif /* #ifdef CONFIG_TASKS_RCU */
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
@@ -1999,29 +2012,21 @@
extern void task_clear_jobctl_pending(struct task_struct *task,
unsigned int mask);
+static inline void rcu_copy_process(struct task_struct *p)
+{
#ifdef CONFIG_PREEMPT_RCU
-
-#define RCU_READ_UNLOCK_BLOCKED (1 << 0) /* blocked while in RCU read-side. */
-#define RCU_READ_UNLOCK_NEED_QS (1 << 1) /* RCU core needs CPU response. */
-
-static inline void rcu_copy_process(struct task_struct *p)
-{
p->rcu_read_lock_nesting = 0;
- p->rcu_read_unlock_special = 0;
-#ifdef CONFIG_TREE_PREEMPT_RCU
+ p->rcu_read_unlock_special.s = 0;
p->rcu_blocked_node = NULL;
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
INIT_LIST_HEAD(&p->rcu_node_entry);
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
+#ifdef CONFIG_TASKS_RCU
+ p->rcu_tasks_holdout = false;
+ INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
+ p->rcu_tasks_idle_cpu = -1;
+#endif /* #ifdef CONFIG_TASKS_RCU */
}
-#else
-
-static inline void rcu_copy_process(struct task_struct *p)
-{
-}
-
-#endif
-
static inline void tsk_restore_flags(struct task_struct *task,
unsigned long orig_flags, unsigned long flags)
{
diff --git a/init/Kconfig b/init/Kconfig
index 64ee4d9..4fe5500 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -507,6 +507,16 @@
This option enables preemptible-RCU code that is common between
TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
+config TASKS_RCU
+ bool "Task_based RCU implementation using voluntary context switch"
+ default n
+ help
+ This option enables a task-based RCU implementation that uses
+ only voluntary context switch (not preemption!), idle, and
+ user-mode execution as quiescent states.
+
+ If unsure, say N.
+
config RCU_STALL_COMMON
def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
help
diff --git a/kernel/exit.c b/kernel/exit.c
index 32c58f7..d13f2ee 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -667,6 +667,7 @@
{
struct task_struct *tsk = current;
int group_dead;
+ TASKS_RCU(int tasks_rcu_i);
profile_task_exit(tsk);
@@ -775,6 +776,7 @@
*/
flush_ptrace_hw_breakpoint(tsk);
+ TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
exit_notify(tsk, group_dead);
proc_exit_connector(tsk);
#ifdef CONFIG_NUMA
@@ -814,6 +816,7 @@
if (tsk->nr_dirtied)
__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
exit_rcu();
+ TASKS_RCU(__srcu_read_unlock(&tasks_rcu_exit_srcu, tasks_rcu_i));
/*
* The setting of TASK_RUNNING by try_to_wake_up() may be delayed
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 0bcd53a..6d15095 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -612,6 +612,52 @@
.name = "sched"
};
+#ifdef CONFIG_TASKS_RCU
+
+/*
+ * Definitions for RCU-tasks torture testing.
+ */
+
+static int tasks_torture_read_lock(void)
+{
+ return 0;
+}
+
+static void tasks_torture_read_unlock(int idx)
+{
+}
+
+static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
+{
+ call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
+}
+
+static struct rcu_torture_ops tasks_ops = {
+ .ttype = RCU_TASKS_FLAVOR,
+ .init = rcu_sync_torture_init,
+ .readlock = tasks_torture_read_lock,
+ .read_delay = rcu_read_delay, /* just reuse rcu's version. */
+ .readunlock = tasks_torture_read_unlock,
+ .completed = rcu_no_completed,
+ .deferred_free = rcu_tasks_torture_deferred_free,
+ .sync = synchronize_rcu_tasks,
+ .exp_sync = synchronize_rcu_tasks,
+ .call = call_rcu_tasks,
+ .cb_barrier = rcu_barrier_tasks,
+ .fqs = NULL,
+ .stats = NULL,
+ .irq_capable = 1,
+ .name = "tasks"
+};
+
+#define RCUTORTURE_TASKS_OPS &tasks_ops,
+
+#else /* #ifdef CONFIG_TASKS_RCU */
+
+#define RCUTORTURE_TASKS_OPS
+
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
/*
* RCU torture priority-boost testing. Runs one real-time thread per
* CPU for moderate bursts, repeatedly registering RCU callbacks and
@@ -678,7 +724,7 @@
}
call_rcu_time = jiffies;
}
- cond_resched();
+ cond_resched_rcu_qs();
stutter_wait("rcu_torture_boost");
if (torture_must_stop())
goto checkwait;
@@ -1082,7 +1128,7 @@
__this_cpu_inc(rcu_torture_batch[completed]);
preempt_enable();
cur_ops->readunlock(idx);
- cond_resched();
+ cond_resched_rcu_qs();
stutter_wait("rcu_torture_reader");
} while (!torture_must_stop());
if (irqreader && cur_ops->irq_capable) {
@@ -1344,7 +1390,8 @@
if (atomic_dec_and_test(&barrier_cbs_count))
wake_up(&barrier_wq);
} while (!torture_must_stop());
- cur_ops->cb_barrier();
+ if (cur_ops->cb_barrier != NULL)
+ cur_ops->cb_barrier();
destroy_rcu_head_on_stack(&rcu);
torture_kthread_stopping("rcu_torture_barrier_cbs");
return 0;
@@ -1585,6 +1632,7 @@
int firsterr = 0;
static struct rcu_torture_ops *torture_ops[] = {
&rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &sched_ops,
+ RCUTORTURE_TASKS_OPS
};
if (!torture_init_begin(torture_type, verbose, &rcutorture_runnable))
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 4a55a24..c0623fc 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -72,7 +72,7 @@
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
- rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+ rcu_sched_qs(); /* implies rcu_bh_inc() */
barrier();
rcu_dynticks_nesting = newval;
}
@@ -217,7 +217,7 @@
* are at it, given that any rcu quiescent state is also an rcu_bh
* quiescent state. Use "+" instead of "||" to defeat short circuiting.
*/
-void rcu_sched_qs(int cpu)
+void rcu_sched_qs(void)
{
unsigned long flags;
@@ -231,7 +231,7 @@
/*
* Record an rcu_bh quiescent state.
*/
-void rcu_bh_qs(int cpu)
+void rcu_bh_qs(void)
{
unsigned long flags;
@@ -251,9 +251,11 @@
{
RCU_TRACE(check_cpu_stalls());
if (user || rcu_is_cpu_rrupt_from_idle())
- rcu_sched_qs(cpu);
+ rcu_sched_qs();
else if (!in_softirq())
- rcu_bh_qs(cpu);
+ rcu_bh_qs();
+ if (user)
+ rcu_note_voluntary_context_switch(current);
}
/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index be0d0a1b..d7a3b13 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -197,22 +197,24 @@
* one since the start of the grace period, this just sets a flag.
* The caller must have disabled preemption.
*/
-void rcu_sched_qs(int cpu)
+void rcu_sched_qs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
+ if (!__this_cpu_read(rcu_sched_data.passed_quiesce)) {
+ trace_rcu_grace_period(TPS("rcu_sched"),
+ __this_cpu_read(rcu_sched_data.gpnum),
+ TPS("cpuqs"));
+ __this_cpu_write(rcu_sched_data.passed_quiesce, 1);
+ }
}
-void rcu_bh_qs(int cpu)
+void rcu_bh_qs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
+ if (!__this_cpu_read(rcu_bh_data.passed_quiesce)) {
+ trace_rcu_grace_period(TPS("rcu_bh"),
+ __this_cpu_read(rcu_bh_data.gpnum),
+ TPS("cpuqs"));
+ __this_cpu_write(rcu_bh_data.passed_quiesce, 1);
+ }
}
static DEFINE_PER_CPU(int, rcu_sched_qs_mask);
@@ -287,7 +289,7 @@
void rcu_note_context_switch(int cpu)
{
trace_rcu_utilization(TPS("Start context switch"));
- rcu_sched_qs(cpu);
+ rcu_sched_qs();
rcu_preempt_note_context_switch(cpu);
if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
rcu_momentary_dyntick_idle();
@@ -535,6 +537,7 @@
atomic_inc(&rdtp->dynticks);
smp_mb__after_atomic(); /* Force ordering with next sojourn. */
WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
+ rcu_dynticks_task_enter();
/*
* It is illegal to enter an extended quiescent state while
@@ -651,6 +654,7 @@
static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
int user)
{
+ rcu_dynticks_task_exit();
smp_mb__before_atomic(); /* Force ordering w/previous sojourn. */
atomic_inc(&rdtp->dynticks);
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
@@ -1656,7 +1660,7 @@
rnp->level, rnp->grplo,
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq(&rnp->lock);
- cond_resched();
+ cond_resched_rcu_qs();
}
mutex_unlock(&rsp->onoff_mutex);
@@ -1746,7 +1750,7 @@
/* smp_mb() provided by prior unlock-lock pair. */
nocb += rcu_future_gp_cleanup(rsp, rnp);
raw_spin_unlock_irq(&rnp->lock);
- cond_resched();
+ cond_resched_rcu_qs();
}
rnp = rcu_get_root(rsp);
raw_spin_lock_irq(&rnp->lock);
@@ -1795,7 +1799,7 @@
/* Locking provides needed memory barrier. */
if (rcu_gp_init(rsp))
break;
- cond_resched();
+ cond_resched_rcu_qs();
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
@@ -1838,10 +1842,10 @@
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqsend"));
- cond_resched();
+ cond_resched_rcu_qs();
} else {
/* Deal with stray signal. */
- cond_resched();
+ cond_resched_rcu_qs();
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
@@ -2401,8 +2405,8 @@
* at least not while the corresponding CPU is online.
*/
- rcu_sched_qs(cpu);
- rcu_bh_qs(cpu);
+ rcu_sched_qs();
+ rcu_bh_qs();
} else if (!in_softirq()) {
@@ -2413,11 +2417,13 @@
* critical section, so note it.
*/
- rcu_bh_qs(cpu);
+ rcu_bh_qs();
}
rcu_preempt_check_callbacks(cpu);
if (rcu_pending(cpu))
invoke_rcu_core();
+ if (user)
+ rcu_note_voluntary_context_switch(current);
trace_rcu_utilization(TPS("End scheduler-tick"));
}
@@ -2440,7 +2446,7 @@
struct rcu_node *rnp;
rcu_for_each_leaf_node(rsp, rnp) {
- cond_resched();
+ cond_resched_rcu_qs();
mask = 0;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index ffedcb9..d037646 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -615,6 +615,8 @@
static void rcu_bind_gp_kthread(void);
static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp);
static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
+static void rcu_dynticks_task_enter(void);
+static void rcu_dynticks_task_exit(void);
#endif /* #ifndef RCU_TREE_NONCORE */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 59318ea..e2c5910 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -128,18 +128,19 @@
* not in a quiescent state. There might be any number of tasks blocked
* while in an RCU read-side critical section.
*
- * Unlike the other rcu_*_qs() functions, callers to this function
- * must disable irqs in order to protect the assignment to
- * ->rcu_read_unlock_special.
+ * As with the other rcu_*_qs() functions, callers to this function
+ * must disable preemption.
*/
-static void rcu_preempt_qs(int cpu)
+static void rcu_preempt_qs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_preempt"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
- current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
+ if (!__this_cpu_read(rcu_preempt_data.passed_quiesce)) {
+ trace_rcu_grace_period(TPS("rcu_preempt"),
+ __this_cpu_read(rcu_preempt_data.gpnum),
+ TPS("cpuqs"));
+ __this_cpu_write(rcu_preempt_data.passed_quiesce, 1);
+ barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */
+ current->rcu_read_unlock_special.b.need_qs = false;
+ }
}
/*
@@ -163,14 +164,14 @@
struct rcu_node *rnp;
if (t->rcu_read_lock_nesting > 0 &&
- (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
+ !t->rcu_read_unlock_special.b.blocked) {
/* Possibly blocking in an RCU read-side critical section. */
rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
- t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
+ t->rcu_read_unlock_special.b.blocked = true;
t->rcu_blocked_node = rnp;
/*
@@ -212,7 +213,7 @@
: rnp->gpnum + 1);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
} else if (t->rcu_read_lock_nesting < 0 &&
- t->rcu_read_unlock_special) {
+ t->rcu_read_unlock_special.s) {
/*
* Complete exit from RCU read-side critical section on
@@ -230,9 +231,7 @@
* grace period, then the fact that the task has been enqueued
* means that we continue to block the current grace period.
*/
- local_irq_save(flags);
- rcu_preempt_qs(cpu);
- local_irq_restore(flags);
+ rcu_preempt_qs();
}
/*
@@ -313,7 +312,7 @@
bool drop_boost_mutex = false;
#endif /* #ifdef CONFIG_RCU_BOOST */
struct rcu_node *rnp;
- int special;
+ union rcu_special special;
/* NMI handlers cannot block and cannot safely manipulate state. */
if (in_nmi())
@@ -323,12 +322,13 @@
/*
* If RCU core is waiting for this CPU to exit critical section,
- * let it know that we have done so.
+ * let it know that we have done so. Because irqs are disabled,
+ * t->rcu_read_unlock_special cannot change.
*/
special = t->rcu_read_unlock_special;
- if (special & RCU_READ_UNLOCK_NEED_QS) {
- rcu_preempt_qs(smp_processor_id());
- if (!t->rcu_read_unlock_special) {
+ if (special.b.need_qs) {
+ rcu_preempt_qs();
+ if (!t->rcu_read_unlock_special.s) {
local_irq_restore(flags);
return;
}
@@ -341,8 +341,8 @@
}
/* Clean up if blocked during RCU read-side critical section. */
- if (special & RCU_READ_UNLOCK_BLOCKED) {
- t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED;
+ if (special.b.blocked) {
+ t->rcu_read_unlock_special.b.blocked = false;
/*
* Remove this task from the list it blocked on. The
@@ -626,12 +626,13 @@
struct task_struct *t = current;
if (t->rcu_read_lock_nesting == 0) {
- rcu_preempt_qs(cpu);
+ rcu_preempt_qs();
return;
}
if (t->rcu_read_lock_nesting > 0 &&
- per_cpu(rcu_preempt_data, cpu).qs_pending)
- t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
+ per_cpu(rcu_preempt_data, cpu).qs_pending &&
+ !per_cpu(rcu_preempt_data, cpu).passed_quiesce)
+ t->rcu_read_unlock_special.b.need_qs = true;
}
#ifdef CONFIG_RCU_BOOST
@@ -915,7 +916,7 @@
return;
t->rcu_read_lock_nesting = 1;
barrier();
- t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
+ t->rcu_read_unlock_special.b.blocked = true;
__rcu_read_unlock();
}
@@ -1816,7 +1817,7 @@
get_online_cpus();
for_each_online_cpu(cpu) {
smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1);
- cond_resched();
+ cond_resched_rcu_qs();
}
put_online_cpus();
@@ -3162,3 +3163,19 @@
housekeeping_affine(current);
#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
}
+
+/* Record the current task on dyntick-idle entry. */
+static void rcu_dynticks_task_enter(void)
+{
+#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
+ ACCESS_ONCE(current->rcu_tasks_idle_cpu) = smp_processor_id();
+#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
+}
+
+/* Record no current task on dyntick-idle exit. */
+static void rcu_dynticks_task_exit(void)
+{
+#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
+ ACCESS_ONCE(current->rcu_tasks_idle_cpu) = -1;
+#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
+}
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index ea8ea7b..3ef8ba5 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -47,6 +47,8 @@
#include <linux/hardirq.h>
#include <linux/delay.h>
#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/tick.h>
#define CREATE_TRACE_POINTS
@@ -91,7 +93,7 @@
barrier(); /* critical section before exit code. */
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
- if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
+ if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
@@ -379,3 +381,312 @@
early_initcall(check_cpu_stall_init);
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
+
+#ifdef CONFIG_TASKS_RCU
+
+/*
+ * Simple variant of RCU whose quiescent states are voluntary context switch,
+ * user-space execution, and idle. As such, grace periods can take one good
+ * long time. There are no read-side primitives similar to rcu_read_lock()
+ * and rcu_read_unlock() because this implementation is intended to get
+ * the system into a safe state for some of the manipulations involved in
+ * tracing and the like. Finally, this implementation does not support
+ * high call_rcu_tasks() rates from multiple CPUs. If this is required,
+ * per-CPU callback lists will be needed.
+ */
+
+/* Global list of callbacks and associated lock. */
+static struct rcu_head *rcu_tasks_cbs_head;
+static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
+static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq);
+static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock);
+
+/* Track exiting tasks in order to allow them to be waited for. */
+DEFINE_SRCU(tasks_rcu_exit_srcu);
+
+/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */
+static int rcu_task_stall_timeout __read_mostly = HZ * 60 * 10;
+module_param(rcu_task_stall_timeout, int, 0644);
+
+static void rcu_spawn_tasks_kthread(void);
+
+/*
+ * Post an RCU-tasks callback. First call must be from process context
+ * after the scheduler if fully operational.
+ */
+void call_rcu_tasks(struct rcu_head *rhp, void (*func)(struct rcu_head *rhp))
+{
+ unsigned long flags;
+ bool needwake;
+
+ rhp->next = NULL;
+ rhp->func = func;
+ raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
+ needwake = !rcu_tasks_cbs_head;
+ *rcu_tasks_cbs_tail = rhp;
+ rcu_tasks_cbs_tail = &rhp->next;
+ raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
+ if (needwake) {
+ rcu_spawn_tasks_kthread();
+ wake_up(&rcu_tasks_cbs_wq);
+ }
+}
+EXPORT_SYMBOL_GPL(call_rcu_tasks);
+
+/**
+ * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu-tasks
+ * grace period has elapsed, in other words after all currently
+ * executing rcu-tasks read-side critical sections have elapsed. These
+ * read-side critical sections are delimited by calls to schedule(),
+ * cond_resched_rcu_qs(), idle execution, userspace execution, calls
+ * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
+ *
+ * This is a very specialized primitive, intended only for a few uses in
+ * tracing and other situations requiring manipulation of function
+ * preambles and profiling hooks. The synchronize_rcu_tasks() function
+ * is not (yet) intended for heavy use from multiple CPUs.
+ *
+ * Note that this guarantee implies further memory-ordering guarantees.
+ * On systems with more than one CPU, when synchronize_rcu_tasks() returns,
+ * each CPU is guaranteed to have executed a full memory barrier since the
+ * end of its last RCU-tasks read-side critical section whose beginning
+ * preceded the call to synchronize_rcu_tasks(). In addition, each CPU
+ * having an RCU-tasks read-side critical section that extends beyond
+ * the return from synchronize_rcu_tasks() is guaranteed to have executed
+ * a full memory barrier after the beginning of synchronize_rcu_tasks()
+ * and before the beginning of that RCU-tasks read-side critical section.
+ * Note that these guarantees include CPUs that are offline, idle, or
+ * executing in user mode, as well as CPUs that are executing in the kernel.
+ *
+ * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned
+ * to its caller on CPU B, then both CPU A and CPU B are guaranteed
+ * to have executed a full memory barrier during the execution of
+ * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU
+ * (but again only if the system has more than one CPU).
+ */
+void synchronize_rcu_tasks(void)
+{
+ /* Complain if the scheduler has not started. */
+ rcu_lockdep_assert(!rcu_scheduler_active,
+ "synchronize_rcu_tasks called too soon");
+
+ /* Wait for the grace period. */
+ wait_rcu_gp(call_rcu_tasks);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
+
+/**
+ * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
+ *
+ * Although the current implementation is guaranteed to wait, it is not
+ * obligated to, for example, if there are no pending callbacks.
+ */
+void rcu_barrier_tasks(void)
+{
+ /* There is only one callback queue, so this is easy. ;-) */
+ synchronize_rcu_tasks();
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
+
+/* See if tasks are still holding out, complain if so. */
+static void check_holdout_task(struct task_struct *t,
+ bool needreport, bool *firstreport)
+{
+ int cpu;
+
+ if (!ACCESS_ONCE(t->rcu_tasks_holdout) ||
+ t->rcu_tasks_nvcsw != ACCESS_ONCE(t->nvcsw) ||
+ !ACCESS_ONCE(t->on_rq) ||
+ (IS_ENABLED(CONFIG_NO_HZ_FULL) &&
+ !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
+ ACCESS_ONCE(t->rcu_tasks_holdout) = false;
+ list_del_init(&t->rcu_tasks_holdout_list);
+ put_task_struct(t);
+ return;
+ }
+ if (!needreport)
+ return;
+ if (*firstreport) {
+ pr_err("INFO: rcu_tasks detected stalls on tasks:\n");
+ *firstreport = false;
+ }
+ cpu = task_cpu(t);
+ pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n",
+ t, ".I"[is_idle_task(t)],
+ "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
+ t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
+ t->rcu_tasks_idle_cpu, cpu);
+ sched_show_task(t);
+}
+
+/* RCU-tasks kthread that detects grace periods and invokes callbacks. */
+static int __noreturn rcu_tasks_kthread(void *arg)
+{
+ unsigned long flags;
+ struct task_struct *g, *t;
+ unsigned long lastreport;
+ struct rcu_head *list;
+ struct rcu_head *next;
+ LIST_HEAD(rcu_tasks_holdouts);
+
+ /* FIXME: Add housekeeping affinity. */
+
+ /*
+ * Each pass through the following loop makes one check for
+ * newly arrived callbacks, and, if there are some, waits for
+ * one RCU-tasks grace period and then invokes the callbacks.
+ * This loop is terminated by the system going down. ;-)
+ */
+ for (;;) {
+
+ /* Pick up any new callbacks. */
+ raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
+ list = rcu_tasks_cbs_head;
+ rcu_tasks_cbs_head = NULL;
+ rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
+ raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
+
+ /* If there were none, wait a bit and start over. */
+ if (!list) {
+ wait_event_interruptible(rcu_tasks_cbs_wq,
+ rcu_tasks_cbs_head);
+ if (!rcu_tasks_cbs_head) {
+ WARN_ON(signal_pending(current));
+ schedule_timeout_interruptible(HZ/10);
+ }
+ continue;
+ }
+
+ /*
+ * Wait for all pre-existing t->on_rq and t->nvcsw
+ * transitions to complete. Invoking synchronize_sched()
+ * suffices because all these transitions occur with
+ * interrupts disabled. Without this synchronize_sched(),
+ * a read-side critical section that started before the
+ * grace period might be incorrectly seen as having started
+ * after the grace period.
+ *
+ * This synchronize_sched() also dispenses with the
+ * need for a memory barrier on the first store to
+ * ->rcu_tasks_holdout, as it forces the store to happen
+ * after the beginning of the grace period.
+ */
+ synchronize_sched();
+
+ /*
+ * There were callbacks, so we need to wait for an
+ * RCU-tasks grace period. Start off by scanning
+ * the task list for tasks that are not already
+ * voluntarily blocked. Mark these tasks and make
+ * a list of them in rcu_tasks_holdouts.
+ */
+ rcu_read_lock();
+ for_each_process_thread(g, t) {
+ if (t != current && ACCESS_ONCE(t->on_rq) &&
+ !is_idle_task(t)) {
+ get_task_struct(t);
+ t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw);
+ ACCESS_ONCE(t->rcu_tasks_holdout) = true;
+ list_add(&t->rcu_tasks_holdout_list,
+ &rcu_tasks_holdouts);
+ }
+ }
+ rcu_read_unlock();
+
+ /*
+ * Wait for tasks that are in the process of exiting.
+ * This does only part of the job, ensuring that all
+ * tasks that were previously exiting reach the point
+ * where they have disabled preemption, allowing the
+ * later synchronize_sched() to finish the job.
+ */
+ synchronize_srcu(&tasks_rcu_exit_srcu);
+
+ /*
+ * Each pass through the following loop scans the list
+ * of holdout tasks, removing any that are no longer
+ * holdouts. When the list is empty, we are done.
+ */
+ lastreport = jiffies;
+ while (!list_empty(&rcu_tasks_holdouts)) {
+ bool firstreport;
+ bool needreport;
+ int rtst;
+ struct task_struct *t1;
+
+ schedule_timeout_interruptible(HZ);
+ rtst = ACCESS_ONCE(rcu_task_stall_timeout);
+ needreport = rtst > 0 &&
+ time_after(jiffies, lastreport + rtst);
+ if (needreport)
+ lastreport = jiffies;
+ firstreport = true;
+ WARN_ON(signal_pending(current));
+ list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
+ rcu_tasks_holdout_list) {
+ check_holdout_task(t, needreport, &firstreport);
+ cond_resched();
+ }
+ }
+
+ /*
+ * Because ->on_rq and ->nvcsw are not guaranteed
+ * to have a full memory barriers prior to them in the
+ * schedule() path, memory reordering on other CPUs could
+ * cause their RCU-tasks read-side critical sections to
+ * extend past the end of the grace period. However,
+ * because these ->nvcsw updates are carried out with
+ * interrupts disabled, we can use synchronize_sched()
+ * to force the needed ordering on all such CPUs.
+ *
+ * This synchronize_sched() also confines all
+ * ->rcu_tasks_holdout accesses to be within the grace
+ * period, avoiding the need for memory barriers for
+ * ->rcu_tasks_holdout accesses.
+ *
+ * In addition, this synchronize_sched() waits for exiting
+ * tasks to complete their final preempt_disable() region
+ * of execution, cleaning up after the synchronize_srcu()
+ * above.
+ */
+ synchronize_sched();
+
+ /* Invoke the callbacks. */
+ while (list) {
+ next = list->next;
+ local_bh_disable();
+ list->func(list);
+ local_bh_enable();
+ list = next;
+ cond_resched();
+ }
+ schedule_timeout_uninterruptible(HZ/10);
+ }
+}
+
+/* Spawn rcu_tasks_kthread() at first call to call_rcu_tasks(). */
+static void rcu_spawn_tasks_kthread(void)
+{
+ static DEFINE_MUTEX(rcu_tasks_kthread_mutex);
+ static struct task_struct *rcu_tasks_kthread_ptr;
+ struct task_struct *t;
+
+ if (ACCESS_ONCE(rcu_tasks_kthread_ptr)) {
+ smp_mb(); /* Ensure caller sees full kthread. */
+ return;
+ }
+ mutex_lock(&rcu_tasks_kthread_mutex);
+ if (rcu_tasks_kthread_ptr) {
+ mutex_unlock(&rcu_tasks_kthread_mutex);
+ return;
+ }
+ t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread");
+ BUG_ON(IS_ERR(t));
+ smp_mb(); /* Ensure others see full kthread. */
+ ACCESS_ONCE(rcu_tasks_kthread_ptr) = t;
+ mutex_unlock(&rcu_tasks_kthread_mutex);
+}
+
+#endif /* #ifdef CONFIG_TASKS_RCU */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 5918d22..348ec76 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -278,7 +278,7 @@
pending >>= softirq_bit;
}
- rcu_bh_qs(smp_processor_id());
+ rcu_bh_qs();
local_irq_disable();
pending = local_softirq_pending();
diff --git a/mm/mlock.c b/mm/mlock.c
index ce84cb0..ab3150c 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -789,7 +789,7 @@
/* Ignore errors */
mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
- cond_resched();
+ cond_resched_rcu_qs();
}
out:
return 0;
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST
index cd3d29c..a3a1a05 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST
@@ -11,3 +11,6 @@
SRCU-P
TINY01
TINY02
+TASKS01
+TASKS02
+TASKS03
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS01 b/tools/testing/selftests/rcutorture/configs/rcu/TASKS01
new file mode 100644
index 0000000..97f0a0b
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS01
@@ -0,0 +1,9 @@
+CONFIG_SMP=y
+CONFIG_NR_CPUS=2
+CONFIG_HOTPLUG_CPU=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+CONFIG_DEBUG_LOCK_ALLOC=y
+CONFIG_PROVE_RCU=y
+CONFIG_TASKS_RCU=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS01.boot b/tools/testing/selftests/rcutorture/configs/rcu/TASKS01.boot
new file mode 100644
index 0000000..cd2a188
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS01.boot
@@ -0,0 +1 @@
+rcutorture.torture_type=tasks
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS02 b/tools/testing/selftests/rcutorture/configs/rcu/TASKS02
new file mode 100644
index 0000000..696d2ea7
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS02
@@ -0,0 +1,5 @@
+CONFIG_SMP=n
+CONFIG_PREEMPT_NONE=y
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=n
+CONFIG_TASKS_RCU=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS02.boot b/tools/testing/selftests/rcutorture/configs/rcu/TASKS02.boot
new file mode 100644
index 0000000..cd2a188
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS02.boot
@@ -0,0 +1 @@
+rcutorture.torture_type=tasks
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03 b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03
new file mode 100644
index 0000000..9c60da5
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03
@@ -0,0 +1,13 @@
+CONFIG_SMP=y
+CONFIG_NR_CPUS=2
+CONFIG_HOTPLUG_CPU=n
+CONFIG_SUSPEND=n
+CONFIG_HIBERNATION=n
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+CONFIG_TASKS_RCU=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=n
+CONFIG_NO_HZ_FULL=y
+CONFIG_NO_HZ_FULL_ALL=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot
new file mode 100644
index 0000000..cd2a188
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TASKS03.boot
@@ -0,0 +1 @@
+rcutorture.torture_type=tasks
