freebsd stable - Feb 2012 - pthread_cond_timedwait() broken in 9-stable? (from JAN 10)

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).

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