[GitHub] [incubator-nuttx] zhaoxiu-zeng commented on a change in pull request #5171: semphore: release all semphores' holder that the task held when exit

[GitBox <gi...@apache.org>]

zhaoxiu-zeng commented on a change in pull request #5171:
URL: https://github.com/apache/incubator-nuttx/pull/5171#discussion_r779261590



##########
File path: sched/semaphore/sem_holder.c
##########
@@ -1035,17 +1011,52 @@ void nxsem_release_holder(FAR sem_t *sem)
 {
   FAR struct tcb_s *rtcb = this_task();
   FAR struct semholder_s *pholder;
+  FAR struct semholder_s *candidate = NULL;
+  unsigned int total = 0;
 
   /* Find the container for this holder */
 
-  pholder = nxsem_findholder(sem, rtcb);
-  if (pholder != NULL && pholder->counts > 0)
+#if CONFIG_SEM_PREALLOCHOLDERS > 0
+  for (pholder = sem->hhead; pholder; pholder = pholder->flink)
+    {
+#else
+  int i;
+
+  /* We have two hard-allocated holder structures in sem_t */
+
+  for (i = 0; i < 2; i++)
+    {
+      pholder = &sem->holder[i];
+#endif
+
+      if (pholder->counts <= 0)
+        continue;
+
+      if (pholder->htcb == rtcb)
+        {
+          /* Decrement the counts on this holder -- the holder will be freed
+           * later in nxsem_restore_baseprio.
+           */
+
+          pholder->counts--;
+          return;
+        }
+
+      total++;
+      if (candidate == NULL)
+        candidate = pholder;
+    }
+
+  /* The current task is not a holder */
+
+  if (total == 1)

Review comment:
       If the caller of sem_post is not a holder (such as task1 call sem_wait and task2 call sem_post), nxsem_findholder(sem, rtcb) must return NULL. 
   
   If the semphore's value >= 2, and more than 1 tasks have called sem_wait, the semphore has multi holders.
   
   If the semphore has only one holder, we can decrement the counts immediately.
   Else, it's a bit of a hassle, holders can only be freed until the task exits or the sem destroys.




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