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Date: Thu, 3 Jul 2014 08:35:49 -0700
Message-ID: <CA+55aFy=CnCLet=B9Q5dYU9w885sXNuYVDSkjHAp5V+nczbn3Q@mail.gmail.com>
Subject: Re: [RFC] Cancellable MCS spinlock rework
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jason Low <jason.low2@hp.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@kernel.org>, Waiman Long <Waiman.Long@hp.com>,
        Davidlohr Bueso <davidlohr@hp.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rik van Riel <riel@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>, Peter Anvin <hpa@zytor.com>,
        Andi Kleen <andi@firstfloor.org>,
        Jej B <James.Bottomley@hansenpartnership.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        "Norton, Scott J" <scott.norton@hp.com>,
        "Vinod, Chegu" <chegu_vinod@hp.com>
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Sender: linux-kernel-owner@vger.kernel.org

On Thu, Jul 3, 2014 at 8:31 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I don't think we'll support 2 _billion_ processes/threads waiting on
> the same semaphore any time soon, so the 'long' seems a bit of an
> overkill on 64-bit architectures.

Oh, never mind. The 'struct semaphore' uses it as just a plain count,
but the rwsem ends up splitting up the bits for readers/writers, so we
actually do want the full 64-bit value there.

             Linus
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