1 files changed, 29 insertions, 3 deletions
diff --git a/nuttx/sched/pthread_mutexlock.c b/nuttx/sched/pthread_mutexlock.c
index 753aa2c6b..d5156e461 100644
--- a/nuttx/sched/pthread_mutexlock.c
+++ b/nuttx/sched/pthread_mutexlock.c
@@ -73,13 +73,39 @@
  * Function:  pthread_mutex_lock
  *
  * Description:
- *   Lock a mutex.
+ *   The mutex object referenced by mutex is locked by calling pthread_mutex_lock().
+ *   If the mutex is already locked, the calling thread blocks until the mutex
+ *   becomes available. This operation returns with the mutex object referenced
+ *   by mutex in the locked state with the calling thread as its owner.
+ *
+ *   If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not provided.
+ *   Attempting to relock the mutex causes deadlock. If a thread attempts to unlock
+ *   a mutex that it has not locked or a mutex which is unlocked, undefined behavior
+ *   results.
+ *
+ *   If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is provided.
+ *   If a thread attempts to relock a mutex that it has already locked, an error
+ *   will be returned. If a thread attempts to unlock a mutex that it has not
+ *   locked or a mutex which is unlocked, an error will be returned.
+ *
+ *   If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains the concept
+ *   of a lock count. When a thread successfully acquires a mutex for the first time,
+ *   the lock count is set to one. Every time a thread relocks this mutex, the lock count
+ *   is incremented by one. Each time the thread unlocks the mutex, the lock count is
+ *   decremented by one. When the lock count reaches zero, the mutex becomes available
+ *   for other threads to acquire. If a thread attempts to unlock a mutex that it has
+ *   not locked or a mutex which is unlocked, an error will be returned.
+ *
+ *   If a signal is delivered to a thread waiting for a mutex, upon return from
+ *   the signal handler the thread resumes waiting for the mutex as if it was
+ *   not interrupted.
  *
  * Parameters:
- *   None
+ *   mutex - A reference to the mutex to be locked.
  *
  * Return Value:
- *   None
+ *   0 on success or an errno value on failure.  Note that the errno EINTR
+ *   is never returned by pthread_mutex_lock().
  *
  * Assumptions:
  *