locking/rwsem: Reinit wake_q after use (bcc9a76d) · Commits · 戴 / test

In __rwsem_down_write_failed_common(), the same wake_q variable name is defined twice, with the inner wake_q hiding the one in outer scope. We can either use different names for the two wake_q's. Even better, we can use the same wake_q twice, if necessary. To enable the latter change, we need to define a new helper function wake_q_init() to enable reinitalization of wake_q after use. Signed-off-by:

Waiman Long <longman@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1485052415-9611-1-git-send-email-longman@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -1021,6 +1021,12 @@ struct wake_q_head {
		#define DEFINE_WAKE_Q(name) \
		struct wake_q_head name = { WAKE_Q_TAIL, &name.first }

		static inline void wake_q_init(struct wake_q_head *head)
		{
		head->first = WAKE_Q_TAIL;
		head->lastp = &head->first;
		}

		extern void wake_q_add(struct wake_q_head *head,
		struct task_struct *task);
		extern void wake_up_q(struct wake_q_head *head);

kernel/locking/rwsem-xadd.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -502,8 +502,6 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
		* wake any read locks that were queued ahead of us.
		*/
		if (count > RWSEM_WAITING_BIAS) {
		DEFINE_WAKE_Q(wake_q);

		__rwsem_mark_wake(sem, RWSEM_WAKE_READERS, &wake_q);
		/*
		* The wakeup is normally called _after_ the wait_lock
		@@ -513,6 +511,11 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
		* for attempting rwsem_try_write_lock().
		*/
		wake_up_q(&wake_q);

		/*
		* Reinitialize wake_q after use.
		*/
		wake_q_init(&wake_q);
		}

		} else

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