Correct potenital locking issue in msg allocation

[ric-plt/lib/rmr.git] / src / rmr / common / src / ring_static.c

diff --git a/src/rmr/common/src/ring_static.c b/src/rmr/common/src/ring_static.c
index 8e565fa..7170a9d 100644 (file)
--- a/src/rmr/common/src/ring_static.c
+++ b/src/rmr/common/src/ring_static.c
@@ -75,6 +75,7 @@ static void* uta_mk_ring( int size ) {
                return NULL;
        }
 
+       r->flags = 0;
        r->rgate = NULL;
        r->wgate = NULL;
        r->head = r->tail = 0;
@@ -124,7 +125,7 @@ static int uta_ring_config( void* vr, int options ) {
                }
        }
 
-       if( options & RING_RLOCK ) {
+       if( options & (RING_RLOCK | RING_FRLOCK) ) {                            // read locking
                if( r->rgate == NULL ) {                // don't realloc
                        r->rgate = (pthread_mutex_t *) malloc( sizeof( *r->rgate ) );
                        if( r->rgate == NULL ) {
@@ -133,6 +134,9 @@ static int uta_ring_config( void* vr, int options ) {
        
                        pthread_mutex_init( r->rgate, NULL );
                }
+               if( options & RING_FRLOCK ) {
+                       r->flags |= RING_FL_FLOCK;
+               }
        }
 
        return 1;
@@ -188,8 +192,16 @@ static inline void* uta_ring_extract( void* vr ) {
                return NULL;
        }
 
-       if( r->rgate != NULL ) {                                                // if lock exists we must honour it
-               pthread_mutex_lock( r->rgate );
+       if( r->rgate != NULL ) {                                                        // if lock exists we must honour it
+               if( r->flags & RING_FL_FLOCK ) {                                // fast read locking try once and return nil if we cant lock
+                       if( pthread_mutex_trylock( r->rgate ) != 0 ) {  // quick fail if not able to get a lock
+                               return NULL;
+                       }
+               } else {
+                       if( pthread_mutex_lock( r->rgate ) != 0 ) {
+                               return NULL;
+                       }
+               }
                if( r->tail == r->head ) {                                      // ensure ring didn't go empty while waiting
                        pthread_mutex_unlock( r->rgate );
                        return NULL;
@@ -219,9 +231,13 @@ future -- investigate if it's possible only to set/clear when empty or going to
        return data;
 }
 
+
 /*
        Insert the pointer at the next open space in the ring.
-       Returns 1 if the inert was ok, and 0 if the ring is full.
+       Returns 1 if the inert was ok, and 0 if there is an error;
+       errno will be set to EXFULL if  the ring is full, if the attempt
+       fails with anyt other error that indicates the inability to obtain
+       a lock on the ring.
 */
 static inline int uta_ring_insert( void* vr, void* new_data ) {
        ring_t*         r;
@@ -236,13 +252,16 @@ static inline int uta_ring_insert( void* vr, void* new_data ) {
        }
 
        if( r->wgate != NULL ) {                                                // if lock exists we must honour it
-               pthread_mutex_lock( r->wgate );
+               if( pthread_mutex_lock( r->wgate ) != 0 ) {
+                       return 0;                                                               // leave mutex reason in place
+               }
        }
 
        if( r->head+1 == r->tail || (r->head+1 >= r->nelements && !r->tail) ) {         // ring is full
-               if( r->wgate != NULL ) {                                        // ensure released if needed
+               if( r->wgate != NULL ) {                                                                                                // ensure released if needed
                        pthread_mutex_unlock( r->wgate );
                }
+               errno = EXFULL;
                return 0;
        }