rcu: Make SRCU mandatory
Kernels configured with CONFIG_PRINTK=n and CONFIG_SRCU=n get build
failures. This causes trouble for deep embedded systems. But given
that there are more than 25 instances of "select SRCU" in the kernel,
it is hard to believe that there are many kernels running in production
without SRCU. This commit therefore makes SRCU mandatory. The SRCU
Kconfig option remains for backwards compatibility, and will be removed
when it is no longer used.
[ paulmck: Update per kernel test robot feedback. ]
Reported-by: John Ogness <john.ogness@linutronix.de>
Reported-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: <linux-arch@vger.kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: John Ogness <john.ogness@linutronix.de>
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 768196a..d40b21e 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -154,11 +154,7 @@
return false;
}
static inline void rcu_preempt_deferred_qs(struct task_struct *t) { }
-#ifdef CONFIG_SRCU
void rcu_scheduler_starting(void);
-#else /* #ifndef CONFIG_SRCU */
-static inline void rcu_scheduler_starting(void) { }
-#endif /* #else #ifndef CONFIG_SRCU */
static inline void rcu_end_inkernel_boot(void) { }
static inline bool rcu_inkernel_boot_has_ended(void) { return true; }
static inline bool rcu_is_watching(void) { return true; }
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index f0814ff..9b9d0bb 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -47,11 +47,8 @@
#include <linux/srcutiny.h>
#elif defined(CONFIG_TREE_SRCU)
#include <linux/srcutree.h>
-#elif defined(CONFIG_SRCU)
-#error "Unknown SRCU implementation specified to kernel configuration"
#else
-/* Dummy definition for things like notifiers. Actual use gets link error. */
-struct srcu_struct { };
+#error "Unknown SRCU implementation specified to kernel configuration"
#endif
void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
@@ -78,11 +75,7 @@
}
#endif /* CONFIG_NEED_SRCU_NMI_SAFE */
-#ifdef CONFIG_SRCU
void srcu_init(void);
-#else /* #ifdef CONFIG_SRCU */
-static inline void srcu_init(void) { }
-#endif /* #else #ifdef CONFIG_SRCU */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index f53ad63..1b0d79b 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -54,21 +54,17 @@
Say N if you are unsure.
config SRCU
- bool
- help
- This option selects the sleepable version of RCU. This version
- permits arbitrary sleeping or blocking within RCU read-side critical
- sections.
+ def_bool y
config TINY_SRCU
bool
- default y if SRCU && TINY_RCU
+ default y if TINY_RCU
help
This option selects the single-CPU non-preemptible version of SRCU.
config TREE_SRCU
bool
- default y if SRCU && !TINY_RCU
+ default y if !TINY_RCU
help
This option selects the full-fledged version of SRCU.
@@ -77,7 +73,6 @@
config TASKS_RCU_GENERIC
def_bool TASKS_RCU || TASKS_RUDE_RCU || TASKS_TRACE_RCU
- select SRCU
help
This option enables generic infrastructure code supporting
task-based RCU implementations. Not for manual selection.
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 1b0c41d..232e29f 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -27,7 +27,6 @@
tristate "performance tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
- select SRCU
default n
help
This option provides a kernel module that runs performance
@@ -43,7 +42,6 @@
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
- select SRCU
default n
help
This option provides a kernel module that runs torture tests
@@ -59,7 +57,6 @@
tristate "Scalability tests for read-side synchronization (RCU and others)"
depends on DEBUG_KERNEL
select TORTURE_TEST
- select SRCU
default n
help
This option provides a kernel module that runs performance tests
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index be5979d..1f7ca48 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -286,7 +286,7 @@
*/
extern void resched_cpu(int cpu);
-#if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU)
+#if !defined(CONFIG_TINY_RCU)
#include <linux/rcu_node_tree.h>
@@ -375,6 +375,10 @@
(cpu) <= rnp->grphi; \
(cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
+#endif /* !defined(CONFIG_TINY_RCU) */
+
+#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC)
+
/*
* Wrappers for the rcu_node::lock acquire and release.
*
@@ -437,7 +441,7 @@
#define raw_lockdep_assert_held_rcu_node(p) \
lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
-#endif /* #if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) */
+#endif // #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC)
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 738842c..f5e6a2f 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -224,7 +224,7 @@
synchronize_rcu_expedited();
}
-#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
+#if !defined(CONFIG_TINY_RCU)
/*
* Switch to run-time mode once RCU has fully initialized.
@@ -239,7 +239,7 @@
}
core_initcall(rcu_set_runtime_mode);
-#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
+#endif /* #if !defined(CONFIG_TINY_RCU) */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
@@ -559,10 +559,8 @@
struct early_boot_kfree_rcu *rhp;
call_rcu(&head, test_callback);
- if (IS_ENABLED(CONFIG_SRCU)) {
- early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
- call_srcu(&early_srcu, &shead, test_callback);
- }
+ early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
+ call_srcu(&early_srcu, &shead, test_callback);
rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
if (!WARN_ON_ONCE(!rhp))
kfree_rcu(rhp, rh);
@@ -585,11 +583,9 @@
if (rcu_self_test) {
early_boot_test_counter++;
rcu_barrier();
- if (IS_ENABLED(CONFIG_SRCU)) {
- early_boot_test_counter++;
- srcu_barrier(&early_srcu);
- WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
- }
+ early_boot_test_counter++;
+ srcu_barrier(&early_srcu);
+ WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
}
if (rcu_self_test_counter != early_boot_test_counter) {
WARN_ON(1);
