+/*
+ * Readers-Writer Lock
+ */
+
+typedef struct clib_rw_lock_
+{
+ CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
+ volatile u32 n_readers;
+ volatile u32 n_readers_lock;
+ volatile u32 writer_lock;
+#if CLIB_DEBUG > 0
+ pid_t pid;
+ uword thread_index;
+ void *frame_address;
+#endif
+} *clib_rwlock_t;
+
+always_inline void
+clib_rwlock_init (clib_rwlock_t * p)
+{
+ *p = clib_mem_alloc_aligned (CLIB_CACHE_LINE_BYTES, CLIB_CACHE_LINE_BYTES);
+ memset ((void *) *p, 0, CLIB_CACHE_LINE_BYTES);
+}
+
+always_inline void
+clib_rwlock_free (clib_rwlock_t * p)
+{
+ if (*p)
+ {
+ clib_mem_free ((void *) *p);
+ *p = 0;
+ }
+}
+
+always_inline void
+clib_rwlock_reader_lock (clib_rwlock_t * p)
+{
+ while (__sync_lock_test_and_set (&(*p)->n_readers_lock, 1))
+ CLIB_PAUSE ();
+
+ (*p)->n_readers += 1;
+ if ((*p)->n_readers == 1)
+ {
+ while (__sync_lock_test_and_set (&(*p)->writer_lock, 1))
+ CLIB_PAUSE ();
+ }
+ CLIB_MEMORY_BARRIER ();
+ (*p)->n_readers_lock = 0;
+
+ CLIB_LOCK_DBG (p);
+}
+
+always_inline void
+clib_rwlock_reader_unlock (clib_rwlock_t * p)
+{
+ ASSERT ((*p)->n_readers > 0);
+ CLIB_LOCK_DBG_CLEAR (p);
+
+ while (__sync_lock_test_and_set (&(*p)->n_readers_lock, 1))
+ CLIB_PAUSE ();
+
+ (*p)->n_readers -= 1;
+ if ((*p)->n_readers == 0)
+ {
+ CLIB_MEMORY_BARRIER ();
+ (*p)->writer_lock = 0;
+ }
+
+ CLIB_MEMORY_BARRIER ();
+ (*p)->n_readers_lock = 0;
+}
+
+always_inline void
+clib_rwlock_writer_lock (clib_rwlock_t * p)
+{
+ while (__sync_lock_test_and_set (&(*p)->writer_lock, 1))
+ CLIB_PAUSE ();
+ CLIB_LOCK_DBG (p);
+}
+
+always_inline void
+clib_rwlock_writer_unlock (clib_rwlock_t * p)
+{
+ CLIB_LOCK_DBG_CLEAR (p);
+ CLIB_MEMORY_BARRIER ();
+ (*p)->writer_lock = 0;
+}
+