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Date: Thu, 16 Feb 2012 19:34:37 +0200
From: Andriy Gapon <avg@FreeBSD.org>
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To: Julian Elischer <julian@FreeBSD.org>
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Cc: threads@FreeBSD.org, FreeBSD Stable <freebsd-stable@FreeBSD.org>,
	Jens Axboe <jaxboe@fusionio.com>
Subject: Re: pthread_cond_timedwait() broken in 9-stable? (from JAN 10)
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on 15/02/2012 23:41 Julian Elischer said the following:
> The program fio (an IO test in ports) uses pthreads
> 
> the following code (from fio-2.0.3, but its in earlier code too)
> has suddenly started misbehaving.
> 
>         clock_gettime(CLOCK_REALTIME, &t);
>         t.tv_sec += seconds + 10;
> 
>         pthread_mutex_lock(&mutex->lock);
> 
>         while (!mutex->value && !ret) {
>                 mutex->waiters++;
>                 ret = pthread_cond_timedwait(&mutex->cond, &mutex->lock, &t);
>                 mutex->waiters--;
>         }
> 
>         if (!ret) {
>                 mutex->value--;
>                 pthread_mutex_unlock(&mutex->lock);
>         }
> 
> 
> It turns out that 'ret' sometimes comes back instantly (on my machine) with a
> value of 60 (ETIMEDOUT)
> despite the fact that we set the timeout 10 seconds into the future.
> 
> Has anyone else seen anything like this?
> (and yes the condition variable attribute have been set to use the REALTIME clock).

But why?

Just a hypothesis that maybe there is some issue with time keeping on that system.
How would that code work out for you with MONOTONIC?

-- 
Andriy Gapon