vppinfra: refactor use of CLIB_MEMORY_BARRIER ()

All instances of test_and_set locks used the following sequence
to release the locks:

CLIB_MEMORY_BARRIER ();
p->lock = 0; // p is a generic struct with a TAS lock

Use clib_atomic_release to generate more efficient assembly code.

Type: refactor

Change-Id: Idca3a38b1cf43578108bdd1afe83b6ebc17a4c68
Signed-off-by: Jason Zhang <jason.zhang2@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Lijian Zhang <Lijian.Zhang@arm.com>

3 files changed, 8 insertions, 17 deletions

diff --git a/src/vppinfra/elog.c b/src/vppinfra/elog.c
index 489ccf436d9..caddf6f3757 100644
--- a/src/vppinfra/elog.c
+++ b/src/vppinfra/elog.c
@@ -56,8 +56,7 @@ elog_unlock (elog_main_t * em)
 {
   if (PREDICT_FALSE (em->lock != 0))
     {
-      CLIB_MEMORY_BARRIER ();
-      *em->lock = 0;
+      clib_atomic_release (em->lock);
     }
 }
 
diff --git a/src/vppinfra/lock.h b/src/vppinfra/lock.h
index 337c5a3f0ad..59ab0e33c51 100644
--- a/src/vppinfra/lock.h
+++ b/src/vppinfra/lock.h
@@ -89,9 +89,8 @@ static_always_inline void
 clib_spinlock_unlock (clib_spinlock_t * p)
 {
   CLIB_LOCK_DBG_CLEAR (p);
-  /* Make sure all writes are complete before releasing the lock */
-  CLIB_MEMORY_BARRIER ();
-  (*p)->lock = 0;
+  /* Make sure all reads/writes are complete before releasing the lock */
+  clib_atomic_release (&(*p)->lock);
 }
 
 static_always_inline void
@@ -147,9 +146,7 @@ clib_rwlock_reader_lock (clib_rwlock_t * p)
       while (clib_atomic_test_and_set (&(*p)->writer_lock))
 	CLIB_PAUSE ();
     }
-  CLIB_MEMORY_BARRIER ();
-  (*p)->n_readers_lock = 0;
-
+  clib_atomic_release (&(*p)->n_readers_lock);
   CLIB_LOCK_DBG (p);
 }
 
@@ -165,12 +162,9 @@ clib_rwlock_reader_unlock (clib_rwlock_t * p)
   (*p)->n_readers -= 1;
   if ((*p)->n_readers == 0)
     {
-      CLIB_MEMORY_BARRIER ();
-      (*p)->writer_lock = 0;
+      clib_atomic_release (&(*p)->writer_lock);
     }
-
-  CLIB_MEMORY_BARRIER ();
-  (*p)->n_readers_lock = 0;
+  clib_atomic_release (&(*p)->n_readers_lock);
 }
 
 always_inline void
@@ -185,8 +179,7 @@ always_inline void
 clib_rwlock_writer_unlock (clib_rwlock_t * p)
 {
   CLIB_LOCK_DBG_CLEAR (p);
-  CLIB_MEMORY_BARRIER ();
-  (*p)->writer_lock = 0;
+  clib_atomic_release (&(*p)->writer_lock);
 }
 
 #endif
diff --git a/src/vppinfra/mheap.c b/src/vppinfra/mheap.c
index 2769838d4ba..b5566bd6389 100644
--- a/src/vppinfra/mheap.c
+++ b/src/vppinfra/mheap.c
@@ -82,8 +82,7 @@ mheap_maybe_unlock (void *v)
       if (--h->recursion_count == 0)
 	{
 	  h->owner_cpu = ~0;
-	  CLIB_MEMORY_BARRIER ();
-	  h->lock = 0;
+	  clib_atomic_release (&h->lock);
 	}
     }
 }