use acquire/release in SkEventTracer.cpp

BUG=chromium:437044

Review URL: https://codereview.chromium.org/1091283006

diff --git a/src/utils/SkEventTracer.cpp b/src/utils/SkEventTracer.cpp
index 1a669a3..b114c21 100644 (file)
--- a/src/utils/SkEventTracer.cpp
+++ b/src/utils/SkEventTracer.cpp
@@ -41,18 +41,15 @@ class SkDefaultEventTracer : public SkEventTracer {
 static SkEventTracer* gUserTracer = nullptr;
 SK_DECLARE_STATIC_LAZY_PTR(SkDefaultEventTracer, gDefaultTracer);
 
-// We can use relaxed memory order for gUserTracer loads and stores.
-// It's not guarding anything but itself.
-
 void SkEventTracer::SetInstance(SkEventTracer* tracer) {
-    SkASSERT(nullptr == sk_atomic_load(&gUserTracer, sk_memory_order_relaxed));
-    sk_atomic_store(&gUserTracer, tracer, sk_memory_order_relaxed);
+    SkASSERT(nullptr == sk_atomic_load(&gUserTracer, sk_memory_order_acquire));
+    sk_atomic_store(&gUserTracer, tracer, sk_memory_order_release);
     // An atomic load during process shutdown is probably overkill, but safe overkill.
-    atexit([](){ SkDELETE(sk_atomic_load(&gUserTracer, sk_memory_order_relaxed)); });
+    atexit([](){ SkDELETE(sk_atomic_load(&gUserTracer, sk_memory_order_acquire)); });
 }
 
 SkEventTracer* SkEventTracer::GetInstance() {
-    if (SkEventTracer* tracer = sk_atomic_load(&gUserTracer, sk_memory_order_relaxed)) {
+    if (SkEventTracer* tracer = sk_atomic_load(&gUserTracer, sk_memory_order_acquire)) {
         return tracer;
     }
     return gDefaultTracer.get();