[PATCH] futex_requeue() optimization (59e0e0ac) · Commits · 戴 / test

In futex_requeue(), when the 2 futexes keys hash to the same bucket, there is no need to move the futex_q to the end of the bucket list. Signed-off-by:

Sebastien Dugue <sebastien.dugue@bull.net> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

kernel/futex.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -827,17 +827,20 @@ static int futex_requeue(u32 __user uaddr1, u32 __user uaddr2,
		if (++ret <= nr_wake) {
		wake_futex(this);
		} else {
		/*
		* If key1 and key2 hash to the same bucket, no need to
		* requeue.
		*/
		if (likely(head1 != &hb2->chain)) {
		list_move_tail(&this->list, &hb2->chain);
		this->lock_ptr = &hb2->lock;
		}
		this->key = key2;
		get_key_refs(&key2);
		drop_count++;

		if (ret - nr_wake >= nr_requeue)
		break;
		/* Make sure to stop if key1 == key2: */
		if (head1 == &hb2->chain && head1 != &next->list)
		head1 = &this->list;
		}
		}

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