pussuw commented on code in PR #16194:
URL: https://github.com/apache/nuttx/pull/16194#discussion_r2058968249
##########
sched/semaphore/sem_waitirq.c:
##########
@@ -72,30 +72,54 @@ void nxsem_wait_irq(FAR struct tcb_s *wtcb, int errcode)
{
FAR struct tcb_s *rtcb = this_task();
FAR sem_t *sem = wtcb->waitobj;
+ const bool mutex = NXSEM_IS_MUTEX(sem);
/* It is possible that an interrupt/context switch beat us to the punch
* and already changed the task's state.
*/
- DEBUGASSERT(sem != NULL && atomic_read(NXSEM_COUNT(sem)) < 0);
+ DEBUGASSERT(sem != NULL &&
+ (mutex || atomic_read(NXSEM_COUNT(sem)) < 0) &&
+ (!mutex ||
+ (atomic_read(NXSEM_MHOLDER(sem)) & NXSEM_MBLOCKS_BIT)));
+
+ /* Mutex is never interrupted by a signal */
+
+ if (mutex && errcode == EINTR)
+ {
+ return;
+ }
/* Restore the correct priority of all threads that hold references
* to this semaphore.
*/
nxsem_canceled(wtcb, sem);
- /* And increment the count on the semaphore. This releases the count
- * that was taken by sem_post(). This count decremented the semaphore
- * count to negative and caused the thread to be blocked in the first
- * place.
+ /* Remove task from waiting list */
+
+ dq_rem((FAR dq_entry_t *)wtcb, SEM_WAITLIST(sem));
+
+ /* This restores the value to what it was before the previous sem_wait.
+ * This caused the thread to be blocked in the first place.
*/
- atomic_fetch_add(NXSEM_COUNT(sem), 1);
+ if (mutex)
Review Comment:
To prevent races the new holder should maybe be set here rather than in
nxsem_wait
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