From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
To: Terry Fryar <terry.fryar@domain.hid>
Cc: xenomai@xenomai.org
Subject: Re: [Xenomai-help] Use of condition vars
Date: Fri, 30 Dec 2011 00:56:26 +0100 [thread overview]
Message-ID: <4EFCFE2A.8070505@domain.hid> (raw)
In-Reply-To: <32A50F80EA7447F2B43C6A65BED53790@domain.hid>
On 12/29/2011 09:39 PM, Terry Fryar wrote:
> Using Xenomai 2.6.0, I have a question regarding the use of condition
> variables. I think I understand why the mutex is required, but how to use
> it is a bit of a mystery?
>
> - To call "rt_cond_signal()", do you have to have the mutex acquired??
>
> - I assume to call "rt_cond_wait()", you are required to have the mutex
> acquired, yes??
You have to hold the mutex both for rt_cond_signal() and rt_cond_wait().
The following exercpt from linuxthreads man pages explains it:
A condition variable must always be associated with a mutex, to avoid
the race condition where a thread prepares to wait on a condition vari‐
able and another thread signals the condition just before the first
thread actually waits on it.
--
Gilles.
next prev parent reply other threads:[~2011-12-29 23:56 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-29 20:39 [Xenomai-help] Use of condition vars Terry Fryar
2011-12-29 23:56 ` Gilles Chanteperdrix [this message]
2012-01-02 14:03 ` Terry Fryar
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