OpenCensus: Fix data race (#31255)

src/cpp/ext/filters/census/grpc_plugin.cc

@@ -22,6 +22,8 @@
 
 #include <limits.h>
 
+#include <atomic>
+
 #include "absl/base/attributes.h"
 #include "opencensus/tags/tag_key.h"
 #include "opencensus/trace/span.h"
@@ -161,8 +163,8 @@ ABSL_CONST_INIT const absl::string_view kRpcServerServerLatencyMeasureName =
 ABSL_CONST_INIT const absl::string_view kRpcServerStartedRpcsMeasureName =
     "grpc.io/server/started_rpcs";
 
-bool g_open_census_stats_enabled = true;
-bool g_open_census_tracing_enabled = true;
+std::atomic<bool> g_open_census_stats_enabled(true);
+std::atomic<bool> g_open_census_tracing_enabled(true);
 
 void EnableOpenCensusStats(bool enable) {
   g_open_census_stats_enabled = enable;
@@ -172,8 +174,12 @@ void EnableOpenCensusTracing(bool enable) {
   g_open_census_tracing_enabled = enable;
 }
 
-bool OpenCensusStatsEnabled() { return g_open_census_stats_enabled; }
+bool OpenCensusStatsEnabled() {
+  return g_open_census_stats_enabled.load(std::memory_order_relaxed);
+}
 
-bool OpenCensusTracingEnabled() { return g_open_census_tracing_enabled; }
+bool OpenCensusTracingEnabled() {
+  return g_open_census_tracing_enabled.load(std::memory_order_relaxed);
+}
 
 }  // namespace grpc