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From: Richard Cochran <richardcochran@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH] posix clocks: replace mutex with reader/writer semaphore
Date: Thu, 14 Apr 2011 20:04:59 +0200	[thread overview]
Message-ID: <20110414180458.GA24534@riccoc20.at.omicron.at> (raw)
In-Reply-To: <alpine.LFD.2.00.1103301541000.22418@localhost6.localdomain6>

On Wed, Mar 30, 2011 at 03:41:40PM +0200, Thomas Gleixner wrote:
> On Wed, 30 Mar 2011, Richard Cochran wrote:
> 
> > A dynamic posix clock is protected from asynchronous removal by a mutex.
> > However, using a mutex has the unwanted effect that a long running clock
> > operation in one process will unnecessarily block other processes.
> > 
> > For example, one process might call read() to get an external time stamp
> > coming in at one pulse per second. A second process calling clock_gettime
> > would have to wait for almost a whole second.
> > 
> > This patch fixes the issue by using a reader/writer semaphore instead of
> > a mutex.
> 
> Yuck. /me wonders why we did not see that during the review :)

Thomas,

I don't see this in -rc3, but I think it should go in.
Can you please take this one?

Thanks,

Richard



      reply	other threads:[~2011-04-14 18:05 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-03-30 13:24 [PATCH] posix clocks: replace mutex with reader/writer semaphore Richard Cochran
2011-03-30 13:41 ` Thomas Gleixner
2011-04-14 18:04   ` Richard Cochran [this message]

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