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

After the commit 617f3ef951 ("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: Yanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20211013134154.1085649-4-yanfei.xu@windriver.com
This commit is contained in:
Yanfei Xu 2021-10-13 21:41:54 +08:00 committed by Peter Zijlstra
parent 6c2787f2a2
commit 5197fcd09a
1 changed files with 1 additions and 2 deletions
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3
kernel/locking/rwsem.c
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@ -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;
}