From: Peter Hurley <peter@hurleysoftware.com>
To: Waiman Long <Waiman.Long@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Davidlohr Bueso <dave@stgolabs.net>,
Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [PATCH v3 3/4] locking/rwsem: Improve reader wakeup code
Date: Tue, 17 May 2016 10:30:24 -0700 [thread overview]
Message-ID: <573B5530.2060301@hurleysoftware.com> (raw)
In-Reply-To: <1463093811-10684-4-git-send-email-Waiman.Long@hpe.com>
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@hurleysoftware.com>
next prev parent reply other threads:[~2016-05-17 17:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-12 22:56 [PATCH v3 0/4] locking/rwsem: Add reader-owned state to the owner field Waiman Long
2016-05-12 22:56 ` [PATCH v3 1/4] " Waiman Long
2016-05-12 22:56 ` [PATCH v3 2/4] locking/rwsem: Don't wake up one's own task Waiman Long
2016-05-17 17:45 ` Peter Hurley
2016-05-12 22:56 ` [PATCH v3 3/4] locking/rwsem: Improve reader wakeup code Waiman Long
2016-05-17 17:30 ` Peter Hurley [this message]
2016-05-12 22:56 ` [PATCH v3 4/4] locking/rwsem: Streamline the rwsem_optimistic_spin() code Waiman Long
2016-05-17 17:47 ` Peter Hurley
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