jlaitine commented on code in PR #16194:
URL: https://github.com/apache/nuttx/pull/16194#discussion_r2071312619
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sched/semaphore/sem_wait.c:
##########
@@ -86,19 +89,62 @@ int nxsem_wait_slow(FAR sem_t *sem)
/* Check if the lock is available */
- if (atomic_fetch_sub(NXSEM_COUNT(sem), 1) > 0)
+ if (mutex)
+ {
+ uint32_t mholder;
+
+ /* We lock the mutex for us by setting the blocks bit,
+ * this is all that is needed if we block
+ */
+
+ mholder = atomic_fetch_or(NXSEM_MHOLDER(sem), NXSEM_MBLOCKS_BIT);
+ if (NXSEM_MACQUIRED(mholder))
+ {
+ /* htcb gets NULL if
+ * - the only holder did exit (without posting first)
+ * - the mutex was reset before
+ * In both cases we simply acquire the mutex, thus recovering
+ * from these situations.
+ */
+
+ htcb = nxsched_get_tcb(mholder & (~NXSEM_MBLOCKS_BIT));
+ }
+
+ unlocked = htcb == NULL;
Review Comment:
No this is correct, the unlocked is true if the smaphore is not acquired, or
nxsched_get_tcb returns NULL (which happens in all possible error cases
mentioned in the comment above). The htcb is NULL initially.
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