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From: Thomas Gleixner <tglx@linutronix.de>
To: Richard Cochran <richardcochran@gmail.com>
Cc: linux-kernel@vger.kernel.org, John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH] posix clocks: replace mutex with reader/writer semaphore
Date: Wed, 30 Mar 2011 15:41:40 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.00.1103301541000.22418@localhost6.localdomain6> (raw)
In-Reply-To: <20110330132421.GA31771@riccoc20.at.omicron.at>

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 :)
 

  reply	other threads:[~2011-03-30 13:41 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 [this message]
2011-04-14 18:04   ` Richard Cochran

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