Re: [PATCH v3 3/4] locking/rwsem: Improve reader wakeup code

From: Peter Hurley
Date: Tue May 17 2016 - 13:30:34 EST


On 05/12/2016 03:56 PM, Waiman Long wrote:
> In __rwsem_do_wake(), the reader wakeup code will assume a writer
> has stolen the lock if the active reader/writer count is not 0.
> However, this is not as reliable an indicator as the original
> "< RWSEM_WAITING_BIAS" check. If another reader is present, the code
> will still break out and exit even if the writer is gone. This patch
> changes it to check the same "< RWSEM_WAITING_BIAS" condition to
> reduce the chance of false positive.

Nice.

Reviewed-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>