Commit cd84a42f authored Apr 02, 2009 by Darren Hart Committed by Ingo Molnar Apr 02, 2009

futex: comment requeue key reference semantics

We've tripped over the futex_requeue drop_count refering to key2
instead of key1.  The code is actually correct, but is non-intuitive.
This patch adds an explicit comment explaining the requeue.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 833bb304

kernel/futex.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -883,7 +883,12 @@ retry_private:
		out_unlock:
		double_unlock_hb(hb1, hb2);

		/* drop_futex_key_refs() must be called outside the spinlocks. */
		/*
		* drop_futex_key_refs() must be called outside the spinlocks. During
		* the requeue we moved futex_q's from the hash bucket at key1 to the
		* one at key2 and updated their key pointer. We no longer need to
		* hold the references to key1.
		*/
		while (--drop_count >= 0)
		drop_futex_key_refs(&key1);

Admin message