Commit f123c98e authored Jan 06, 2011 by Steven Rostedt Committed by Ingo Molnar Jan 11, 2011

rtmutex: Fix comment about why new_owner can be NULL in wake_futex_pi()



The comment about why rt_mutex_next_owner() can return NULL in
wake_futex_pi() is not the normal case.

Tracing the cause of why this occurs is more likely that waiter
simply timedout. But because it originally caused contention with
the futex, the owner will go into the kernel when it unlocks
the lock. Then it will hit this code path and
rt_mutex_next_owner() will return NULL.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent cb600d2f

kernel/futex.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -791,10 +791,9 @@ static int wake_futex_pi(u32 __user uaddr, u32 uval, struct futex_q this)
		new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);

		/*
		* This happens when we have stolen the lock and the original
		* pending owner did not enqueue itself back on the rt_mutex.
		* Thats not a tragedy. We know that way, that a lock waiter
		* is on the fly. We make the futex_q waiter the pending owner.
		* It is possible that the next waiter (the one that brought
		* this owner to the kernel) timed out and is no longer
		* waiting on the lock.
		*/
		if (!new_owner)
		new_owner = this->task;

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