> What do you think?
I think this diff is even safer: it checks for threads entering and
exiting the barrier while holding the mutex, and if both values are 0 it
proceeds to destroy the barrier.
I also renamed sofar to in so that the relationship between threads is
more obvious.
Index: rthread.h
===================================================================
RCS file: /cvs/src/lib/librthread/rthread.h,v
retrieving revision 1.55
diff -u -p -r1.55 rthread.h
--- rthread.h 27 Jan 2016 08:40:05 -0000 1.55
+++ rthread.h 16 Mar 2016 12:36:39 -0000
@@ -141,7 +141,8 @@ struct pthread_barrier {
pthread_mutex_t mutex;
pthread_cond_t cond;
int threshold;
- int sofar;
+ int in;
+ int out;
int generation;
};
Index: rthread_barrier.c
===================================================================
RCS file: /cvs/src/lib/librthread/rthread_barrier.c,v
retrieving revision 1.2
diff -u -p -r1.2 rthread_barrier.c
--- rthread_barrier.c 23 Apr 2012 08:30:33 -0000 1.2
+++ rthread_barrier.c 16 Mar 2016 12:36:39 -0000
@@ -74,12 +74,18 @@ pthread_barrier_destroy(pthread_barrier_
if (barrier == NULL || *barrier == NULL)
return (EINVAL);
+ if (pthread_mutex_trylock(&(*barrier)->mutex))
+ return (EBUSY);
+
b = *barrier;
- if (b->sofar > 0)
+ if (b->out > 0 || b->in > 0) {
+ pthread_mutex_unlock(&b->mutex);
return (EBUSY);
+ }
*barrier = NULL;
+ pthread_mutex_unlock(&b->mutex);
pthread_mutex_destroy(&b->mutex);
pthread_cond_destroy(&b->cond);
free(b);
@@ -103,9 +109,10 @@ pthread_barrier_wait(pthread_barrier_t *
if ((rc = pthread_mutex_lock(&b->mutex)))
goto cancel;
- _rthread_debug(6, "sofar: %d, threshold: %d\n", b->sofar, b->threshold);
- if (++b->sofar == b->threshold) {
- b->sofar = 0;
+ _rthread_debug(6, "in: %d, threshold: %d\n", b->in, b->threshold);
+ if (++b->in == b->threshold) {
+ b->out = b->in - 1; /* mark thread exit */
+ b->in = 0;
b->generation++;
if ((rc = pthread_cond_broadcast(&b->cond)))
goto err;
@@ -118,6 +125,7 @@ pthread_barrier_wait(pthread_barrier_t *
if ((rc = pthread_cond_wait(&b->cond, &b->mutex)))
goto err;
} while (gen == b->generation);
+ b->out--; /* mark thread exit */
}
err:
