X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fvppinfra%2Flock.h;h=3cfe11cba17684c194a9bcd1d29b646ba573f111;hb=4c9599574929f624a218b963d268d97799289945;hp=c1f0b87dfc6321307dcb4c5730c7a8814dbddca1;hpb=fb1ccc7c369d879a20567df609d04cfdcec5f8c1;p=vpp.git

diff --git a/src/vppinfra/lock.h b/src/vppinfra/lock.h
index c1f0b87dfc6..3cfe11cba17 100644
--- a/src/vppinfra/lock.h
+++ b/src/vppinfra/lock.h
@@ -21,6 +21,8 @@
 
 #if __x86_64__
 #define CLIB_PAUSE() __builtin_ia32_pause ()
+#elif defined (__aarch64__) || defined (__arm__)
+#define CLIB_PAUSE() __asm__ ("yield")
 #else
 #define CLIB_PAUSE()
 #endif
@@ -118,9 +120,8 @@ clib_spinlock_unlock_if_init (clib_spinlock_t * p)
 typedef struct clib_rw_lock_
 {
   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
-  volatile u32 n_readers;
-  volatile u32 n_readers_lock;
-  volatile u32 writer_lock;
+  /* -1 when W lock held, > 0 when R lock held */
+  volatile i32 rw_cnt;
 #if CLIB_DEBUG > 0
   pid_t pid;
   uword thread_index;
@@ -148,41 +149,37 @@ clib_rwlock_free (clib_rwlock_t * p)
 always_inline void
 clib_rwlock_reader_lock (clib_rwlock_t * p)
 {
-  while (clib_atomic_test_and_set (&(*p)->n_readers_lock))
-    CLIB_PAUSE ();
-
-  (*p)->n_readers += 1;
-  if ((*p)->n_readers == 1)
+  i32 cnt;
+  do
     {
-      while (clib_atomic_test_and_set (&(*p)->writer_lock))
+      /* rwlock held by a writer */
+      while ((cnt = clib_atomic_load_relax_n (&(*p)->rw_cnt)) < 0)
 	CLIB_PAUSE ();
     }
-  clib_atomic_release (&(*p)->n_readers_lock);
+  while (!clib_atomic_cmp_and_swap_acq_relax_n
+	 (&(*p)->rw_cnt, &cnt, cnt + 1, 1));
   CLIB_LOCK_DBG (p);
 }
 
 always_inline void
 clib_rwlock_reader_unlock (clib_rwlock_t * p)
 {
-  ASSERT ((*p)->n_readers > 0);
+  ASSERT ((*p)->rw_cnt > 0);
   CLIB_LOCK_DBG_CLEAR (p);
-
-  while (clib_atomic_test_and_set (&(*p)->n_readers_lock))
-    CLIB_PAUSE ();
-
-  (*p)->n_readers -= 1;
-  if ((*p)->n_readers == 0)
-    {
-      clib_atomic_release (&(*p)->writer_lock);
-    }
-  clib_atomic_release (&(*p)->n_readers_lock);
+  clib_atomic_fetch_sub_rel (&(*p)->rw_cnt, 1);
 }
 
 always_inline void
 clib_rwlock_writer_lock (clib_rwlock_t * p)
 {
-  while (clib_atomic_test_and_set (&(*p)->writer_lock))
-    CLIB_PAUSE ();
+  i32 cnt = 0;
+  do
+    {
+      /* rwlock held by writer or reader(s) */
+      while ((cnt = clib_atomic_load_relax_n (&(*p)->rw_cnt)) != 0)
+	CLIB_PAUSE ();
+    }
+  while (!clib_atomic_cmp_and_swap_acq_relax_n (&(*p)->rw_cnt, &cnt, -1, 1));
   CLIB_LOCK_DBG (p);
 }
 
@@ -190,7 +187,7 @@ always_inline void
 clib_rwlock_writer_unlock (clib_rwlock_t * p)
 {
   CLIB_LOCK_DBG_CLEAR (p);
-  clib_atomic_release (&(*p)->writer_lock);
+  clib_atomic_release (&(*p)->rw_cnt);
 }
 
 #endif