Add support for recursive mutexes

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@753 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 26 insertions, 2 deletions

diff --git a/nuttx/sched/pthread_mutexunlock.c b/nuttx/sched/pthread_mutexunlock.c
index 1184fc804..f01f7761e 100644
--- a/nuttx/sched/pthread_mutexunlock.c
+++ b/nuttx/sched/pthread_mutexunlock.c
@@ -107,14 +107,38 @@ int pthread_mutex_unlock(FAR pthread_mutex_t *mutex)
 
       if (mutex->pid != (int)getpid())
         {
+          /* No... return an error (default behavior is like PTHREAD_MUTEX_ERRORCHECK) */
+
           sdbg("Holder=%d returning EPERM\n", mutex->pid);
           ret = EPERM;
         }
+        
+
+      /* Yes, the caller owns the semaphore.. Is this a recursive mutex? */
+
+#ifdef CONFIG_MUTEX_TYPES
+      else if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->nlocks > 1)
+        {
+          /* This is a recursive mutex and we there are multiple locks held. Retain
+           * the mutex lock, just decrement the count of locks held, and return
+           * success.
+           */
+          mutex->nlocks--;
+        }
+#endif
+
+      /* This is either a non-recursive mutex or is the outermost unlock of
+       * a recursive mutex.
+       */
+
       else
         {
-          /* Nulllify the pid and post the semaphore */
+          /* Nullify the pid and lock count then post the semaphore */
 
-          mutex->pid = 0;
+          mutex->pid    = 0;
+#ifdef CONFIG_MUTEX_TYPES
+          mutex->nlocks = 0;
+#endif
           ret = pthread_givesemaphore((sem_t*)&mutex->sem);
         }
       sched_unlock();