pussuw commented on code in PR #15566:
URL: https://github.com/apache/nuttx/pull/15566#discussion_r1922320948
##########
sched/pthread/pthread_condbroadcast.c:
##########
@@ -68,22 +67,25 @@ int pthread_cond_broadcast(FAR pthread_cond_t *cond)
}
else
{
+ int wcnt = atomic_read(COND_WAIT_COUNT(cond));
+
/* Loop until all of the waiting threads have been restarted. */
- while (cond->wait_count > 0)
+ while (wcnt > 0)
{
- /* If the value is less than zero (meaning that one or more
- * thread is waiting), then post the condition semaphore.
- * Only the highest priority waiting thread will get to execute
- */
+ if (atomic_cmpxchg(COND_WAIT_COUNT(cond), &wcnt, wcnt - 1))
+ {
+ /* If the value is less than zero (meaning that one or more
+ * thread is waiting), then post the condition semaphore.
+ * Only the highest priority waiting thread will get to execute
+ */
- ret = -nxsem_post(&cond->sem);
+ ret = -nxsem_post(&cond->sem);
- /* Increment the semaphore count (as was done by the
- * above post).
- */
+ /* Decrement the waiter count */
- cond->wait_count--;
+ wcnt--;
Review Comment:
No, atomic_cmpxchg updates cond->wait_count but the local copy does not get
modified. Either we need to re-read it here or do the decrement. Otherwise the
while-loop will not work correctly.
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