session/fifo: make event unset atomic

Ensures that fifo cursize loads cannot be speculated to before the event
unset.

Change-Id: Ia7c20c510d58f26a8e9b82d3982c6d4143a3a4d6
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index d7146ae1fb0..6c3940dfad5 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -179,12 +179,12 @@ svm_fifo_set_event (svm_fifo_t * f)
 /**
  * Unsets fifo event flag.
  *
- * Also acts as a release barrier.
+ * Also acts as an acquire barrier.
  */
 always_inline void
 svm_fifo_unset_event (svm_fifo_t * f)
 {
-  clib_atomic_release (&f->has_event);
+  __atomic_exchange_n (&f->has_event, 0, __ATOMIC_ACQUIRE);
 }
 
 svm_fifo_t *svm_fifo_create (u32 data_size_in_bytes);