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Date: Wed, 18 May 2016 12:30:11 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <Waiman.Long@hpe.com>
Cc: 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>,
        Peter Hurley <peter@hurleysoftware.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Scott J Norton <scott.norton@hpe.com>,
        Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [PATCH v4 3/5] locking/rwsem: Don't wake up one's own task
Message-ID: <20160518103011.GC3193@twins.programming.kicks-ass.net>
References: <1463534783-38814-1-git-send-email-Waiman.Long@hpe.com>
 <1463534783-38814-4-git-send-email-Waiman.Long@hpe.com>
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On Tue, May 17, 2016 at 09:26:21PM -0400, Waiman Long wrote:
> As rwsem_down_read_failed() will queue itself and potentially call
> __rwsem_do_wake(sem, RWSEM_WAKE_ANY), it is possible that a reader
> will try to wake up its own task. This patch adds a check to make
> sure that this won't happen.
> 

Yes, this is 'weird', but why are we fixing it at the cost of an extra
branch?