Mark mutex as robust to prevent deadlocks

Prevent application hangs that occur when a thread dies while holding a
mutex, particularly during vTaskEndScheduler or exit calls. This is
achieved by setting the PTHREAD_MUTEX_ROBUST attribute on the mutex.

Fixes:
- GitHub issue: #1217
- Forum thread: freertos.org/t/22287

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>

portable/ThirdParty/GCC/Posix/utils/wait_for_event.c

@@ -35,6 +35,7 @@
 struct event
 {
     pthread_mutex_t mutex;
+    pthread_mutexattr_t mutexattr;
     pthread_cond_t cond;
     bool event_triggered;
 };
@@ -46,7 +47,9 @@ struct event * event_create( void )
     if( ev != NULL )
     {
         ev->event_triggered = false;
-        pthread_mutex_init( &ev->mutex, NULL );
+        pthread_mutexattr_init( &ev->mutexattr );
+        pthread_mutexattr_setrobust( &ev->mutexattr, PTHREAD_MUTEX_ROBUST );
+        pthread_mutex_init( &ev->mutex, &ev->mutexattr );
         pthread_cond_init( &ev->cond, NULL );
     }
 
@@ -56,13 +59,18 @@ struct event * event_create( void )
 void event_delete( struct event * ev )
 {
     pthread_mutex_destroy( &ev->mutex );
+    pthread_mutexattr_destroy( &ev->mutexattr );
     pthread_cond_destroy( &ev->cond );
     free( ev );
 }
 
 bool event_wait( struct event * ev )
 {
-    pthread_mutex_lock( &ev->mutex );
+    if( pthread_mutex_lock( &ev->mutex ) == EOWNERDEAD )
+    {
+        /* If the thread owning the mutex died, make the mutex consistent. */
+        pthread_mutex_consistent( &ev->mutex );
+    }
 
     while( ev->event_triggered == false )
     {
@@ -82,7 +90,11 @@ bool event_wait_timed( struct event * ev,
     clock_gettime( CLOCK_REALTIME, &ts );
     ts.tv_sec += ms / 1000;
     ts.tv_nsec += ( ( ms % 1000 ) * 1000000 );
-    pthread_mutex_lock( &ev->mutex );
+    if( pthread_mutex_lock( &ev->mutex ) == EOWNERDEAD )
+    {
+        /* If the thread owning the mutex died, make the mutex consistent. */
+        pthread_mutex_consistent( &ev->mutex );
+    }
 
     while( ( ev->event_triggered == false ) && ( ret == 0 ) )
     {
@@ -101,7 +113,11 @@ bool event_wait_timed( struct event * ev,
 
 void event_signal( struct event * ev )
 {
-    pthread_mutex_lock( &ev->mutex );
+    if( pthread_mutex_lock( &ev->mutex ) == EOWNERDEAD )
+    {
+        /* If the thread owning the mutex died, make the mutex consistent. */
+        pthread_mutex_consistent( &ev->mutex );
+    }
     ev->event_triggered = true;
     pthread_cond_signal( &ev->cond );
     pthread_mutex_unlock( &ev->mutex );