On 2/16/12 9:34 AM, Andriy Gapon wrote:
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?
Jens Axboe, (CC'd) tried both CLOCK_REALTIME and CLOCK_MONOTONIC, and
they both had the same problem..
i.e. random early returns with ETIMEDOUT.
I think we will try move out machine forward to a newer -stable to see
if it resolves.
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