Justus Winter, le Fri 15 Nov 2013 20:52:23 +0100, a écrit :
> @@ -224,30 +216,22 @@ ports_manage_port_operations_multithread (struct
> port_bucket *bucket,
>
> if (master)
> {
> - pthread_spin_lock (&lock);
> - if (totalthreads != 1)
> - {
> - pthread_spin_unlock (&lock);
> - goto startover;
> - }
> + if (__atomic_load_n (&totalthreads, __ATOMIC_RELAXED) != 1)
> + goto startover;
> }
> else
> {
> - pthread_spin_lock (&lock);
> - if (nreqthreads == 1)
> + __atomic_sub_fetch (&totalthreads, 1, __ATOMIC_RELAXED);
> + if (__atomic_sub_fetch (&nreqthreads, 1, __ATOMIC_RELAXED) == 0)
> {
> /* No other thread is listening for requests, continue. */
> - pthread_spin_unlock (&lock);
> + __atomic_add_fetch (&totalthreads, 1, __ATOMIC_RELAXED);
> + __atomic_add_fetch (&nreqthreads, 1, __ATOMIC_RELAXED);
> goto startover;
> }
> - nreqthreads--;
> - totalthreads--;
> - pthread_spin_unlock (&lock);
> }
Here the totalthreads update should be done after decrementing and
testing nreqthreads (and thus no reincrement if that gives 0). Otherwise
master might see totalthreads being 1 although there is actually another
thread which will happen to realize it'll actually continue. Put
another way, a thread mustn't decrement totalthreads unless it is
absolutely sure it will terminate.
With that fixed, Ack.
Samuel
