sched: Teach might_sleep() about preemptible RCU (234da7bc) · Commits · 戴 / test

In practice, it is harmless to voluntarily sleep in a rcu_read_lock() section if we are running under preempt rcu, but it is illegal if we build a kernel running non-preemptable rcu. Currently, might_sleep() doesn't notice sleepable operations under rcu_read_lock() sections if we are running under preemptable rcu because preempt_count() is left untouched after rcu_read_lock() in this case. But we want developers who test their changes under such config to notice the "sleeping while atomic" issues. So we add rcu_read_lock_nesting to prempt_count() in might_sleep() checks. [ v2: Handle rcu-tiny ] Signed-off-by:

Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> LKML-Reference: <1260991265-8451-1-git-send-regression-fweisbec@gmail.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

include/linux/rcutiny.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -101,4 +101,9 @@ static inline void exit_rcu(void)
		{
		}

		static inline int rcu_preempt_depth(void)
		{
		return 0;
		}

		#endif /* __LINUX_RCUTINY_H */

include/linux/rcutree.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -45,6 +45,12 @@ extern void __rcu_read_unlock(void);
		extern void synchronize_rcu(void);
		extern void exit_rcu(void);

		/*
		* Defined as macro as it is a very low level header
		* included from areas that don't even know about current
		*/
		#define rcu_preempt_depth() (current->rcu_read_lock_nesting)

		#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */

		static inline void __rcu_read_lock(void)
		@@ -63,6 +69,11 @@ static inline void exit_rcu(void)
		{
		}

		static inline int rcu_preempt_depth(void)
		{
		return 0;
		}

		#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */

		static inline void __rcu_read_lock_bh(void)

kernel/sched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -9682,7 +9682,7 @@ void __init sched_init(void)
		#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
		static inline int preempt_count_equals(int preempt_offset)
		{
		int nested = preempt_count() & ~PREEMPT_ACTIVE;
		int nested = (preempt_count() & ~PREEMPT_ACTIVE) + rcu_preempt_depth();

		return (nested == PREEMPT_INATOMIC_BASE + preempt_offset);
		}

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