From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 1/7] locking/rwsem: don't resched at the end of
 optimistic spinning
Date: Mon, 4 Aug 2014 09:55:28 +0200
Message-ID: <20140804075528.GI9918@twins.programming.kicks-ass.net>
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To: Waiman Long <Waiman.Long@hp.com>
Cc: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, Davidlohr Bueso <davidlohr@hp.com>, Jason Low <jason.low2@hp.com>, Scott J Norton <scott.norton@hp.com>
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On Sun, Aug 03, 2014 at 10:36:16PM -0400, Waiman Long wrote:
> For a fully preemptive kernel, a call to preempt_enable() could
> potentially trigger a task rescheduling event. In the case of rwsem
> optimistic spinning, the task has either gotten the lock or is going
> to sleep soon. So there is no point to do rescheduling here.

Uh what? Why shouldn't we preempt if we've gotten the lock? What if a
FIFO task just woke up?=20

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