Commit 5197fcd0 authored by Yanfei Xu's avatar Yanfei Xu Committed by Peter Zijlstra
Browse files

locking/rwsem: Fix comments about reader optimistic lock stealing conditions 



After the commit 617f3ef9 ("locking/rwsem: Remove reader
optimistic spinning"), reader doesn't support optimistic spinning
anymore, there is no need meet the condition which OSQ is empty.

BTW, add an unlikely() for the max reader wakeup check in the loop.

Signed-off-by: default avatarYanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarWaiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20211013134154.1085649-4-yanfei.xu@windriver.com
parent 6c2787f2

kernel/locking/rwsem.c

+1 −2
Original line number Diff line number Diff line
@@ -56,7 +56,6 @@ 
 *

 * A fast path reader optimistic lock stealing is supported when the rwsem

 * is previously owned by a writer and the following conditions are met:

 *  - OSQ is empty

 *  - rwsem is not currently writer owned

 *  - the handoff isn't set.

 */
@@ -485,7 +484,7 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, 
		/*

		 * Limit # of readers that can be woken up per wakeup call.

		 */

		if (woken >= MAX_READERS_WAKEUP)

		if (unlikely(woken >= MAX_READERS_WAKEUP))

			break;

	}