rcu: Deinline rcu_read_lock_sched_held() if DEBUG_LOCK_ALLOC (d5671f6b) · Commits · 戴 / test

include/linux/rcupdate.h

+2 −38

Original line number	Diff line number	Diff line
		@@ -469,46 +469,10 @@ int rcu_read_lock_bh_held(void);
		* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
		* RCU-sched read-side critical section. In absence of
		* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
		* critical section unless it can prove otherwise. Note that disabling
		* of preemption (including disabling irqs) counts as an RCU-sched
		* read-side critical section. This is useful for debug checks in functions
		* that required that they be called within an RCU-sched read-side
		* critical section.
		*
		* Check debug_lockdep_rcu_enabled() to prevent false positives during boot
		* and while lockdep is disabled.
		*
		* Note that if the CPU is in the idle loop from an RCU point of
		* view (ie: that we are in the section between rcu_idle_enter() and
		* rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
		* did an rcu_read_lock(). The reason for this is that RCU ignores CPUs
		* that are in such a section, considering these as in extended quiescent
		* state, so such a CPU is effectively never in an RCU read-side critical
		* section regardless of what RCU primitives it invokes. This state of
		* affairs is required --- we need to keep an RCU-free window in idle
		* where the CPU may possibly enter into low power mode. This way we can
		* notice an extended quiescent state to other CPUs that started a grace
		* period. Otherwise we would delay any grace period as long as we run in
		* the idle task.
		*
		* Similarly, we avoid claiming an SRCU read lock held if the current
		* CPU is offline.
		* critical section unless it can prove otherwise.
		*/
		#ifdef CONFIG_PREEMPT_COUNT
		static inline int rcu_read_lock_sched_held(void)
		{
		int lockdep_opinion = 0;

		if (!debug_lockdep_rcu_enabled())
		return 1;
		if (!rcu_is_watching())
		return 0;
		if (!rcu_lockdep_current_cpu_online())
		return 0;
		if (debug_locks)
		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
		return lockdep_opinion \|\| preempt_count() != 0 \|\| irqs_disabled();
		}
		int rcu_read_lock_sched_held(void);
		#else /* #ifdef CONFIG_PREEMPT_COUNT */
		static inline int rcu_read_lock_sched_held(void)
		{

kernel/rcu/update.c

+49 −0

Original line number	Diff line number	Diff line
		@@ -62,6 +62,55 @@ MODULE_ALIAS("rcupdate");

		module_param(rcu_expedited, int, 0);

		#if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)
		/**
		* rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
		*
		* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
		* RCU-sched read-side critical section. In absence of
		* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
		* critical section unless it can prove otherwise. Note that disabling
		* of preemption (including disabling irqs) counts as an RCU-sched
		* read-side critical section. This is useful for debug checks in functions
		* that required that they be called within an RCU-sched read-side
		* critical section.
		*
		* Check debug_lockdep_rcu_enabled() to prevent false positives during boot
		* and while lockdep is disabled.
		*
		* Note that if the CPU is in the idle loop from an RCU point of
		* view (ie: that we are in the section between rcu_idle_enter() and
		* rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
		* did an rcu_read_lock(). The reason for this is that RCU ignores CPUs
		* that are in such a section, considering these as in extended quiescent
		* state, so such a CPU is effectively never in an RCU read-side critical
		* section regardless of what RCU primitives it invokes. This state of
		* affairs is required --- we need to keep an RCU-free window in idle
		* where the CPU may possibly enter into low power mode. This way we can
		* notice an extended quiescent state to other CPUs that started a grace
		* period. Otherwise we would delay any grace period as long as we run in
		* the idle task.
		*
		* Similarly, we avoid claiming an SRCU read lock held if the current
		* CPU is offline.
		*/
		int rcu_read_lock_sched_held(void)
		{
		int lockdep_opinion = 0;

		if (!debug_lockdep_rcu_enabled())
		return 1;
		if (!rcu_is_watching())
		return 0;
		if (!rcu_lockdep_current_cpu_online())
		return 0;
		if (debug_locks)
		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
		return lockdep_opinion \|\| preempt_count() != 0 \|\| irqs_disabled();
		}
		EXPORT_SYMBOL(rcu_read_lock_sched_held);
		#endif

		#ifndef CONFIG_TINY_RCU

		static atomic_t rcu_expedited_nesting =

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