[tracing] Replace semaphores with {Start,Stop}Blocking

Use Perfetto's Start/StopBlocking() helpers instead of bespoke
synchronization with semaphores.

Cq-Include-Trybots: luci.v8.try:v8_linux64_perfetto_dbg_ng
Bug: v8:8339
Change-Id: If8266d5fa5e3ff6403b9b2e539ec985bc67fcc90
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1728623
Commit-Queue: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Auto-Submit: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63102}

src/libplatform/tracing/tracing-controller.cc

@@ -26,14 +26,10 @@
 class V8DataSource : public perfetto::DataSource<V8DataSource> {
  public:
   void OnSetup(const SetupArgs&) override {}
-  void OnStart(const StartArgs&) override { started_.Signal(); }
+  void OnStart(const StartArgs&) override {}
   void OnStop(const StopArgs&) override {}
-
-  static v8::base::Semaphore started_;
 };
 
-v8::base::Semaphore V8DataSource::started_{0};
-
 PERFETTO_DEFINE_DATA_SOURCE_STATIC_MEMBERS(V8DataSource);
 #endif  // V8_USE_PERFETTO
 
@@ -300,9 +296,7 @@ void TracingController::StartTracing(TraceConfig* trace_config) {
   tracing_session_ =
       perfetto::Tracing::NewTrace(perfetto::BackendType::kUnspecifiedBackend);
   tracing_session_->Setup(perfetto_trace_config);
-  // TODO(petermarshall): Switch to StartBlocking when available.
-  tracing_session_->Start();
-  V8DataSource::started_.Wait();
+  tracing_session_->StartBlocking();
 
 #endif  // V8_USE_PERFETTO
 
@@ -345,10 +339,7 @@ void TracingController::StopTracing() {
   V8DataSource::Trace([&](V8DataSource::TraceContext ctx) {
     auto packet = ctx.NewTracePacket();
   });
-  base::Semaphore stopped_{0};
-  tracing_session_->SetOnStopCallback([&stopped_]() { stopped_.Signal(); });
-  tracing_session_->Stop();
-  stopped_.Wait();
+  tracing_session_->StopBlocking();
 
   std::vector<char> trace = tracing_session_->ReadTraceBlocking();
   json_listener_->ParseFromArray(trace);

test/cctest/libplatform/test-tracing.cc

@@ -23,14 +23,10 @@
 class TestDataSource : public perfetto::DataSource<TestDataSource> {
  public:
   void OnSetup(const SetupArgs&) override {}
-  void OnStart(const StartArgs&) override { started_.Signal(); }
+  void OnStart(const StartArgs&) override {}
   void OnStop(const StopArgs&) override {}
-
-  static v8::base::Semaphore started_;
 };
 
-v8::base::Semaphore TestDataSource::started_{0};
-
 PERFETTO_DEFINE_DATA_SOURCE_STATIC_MEMBERS(TestDataSource);
 #endif  // V8_USE_PERFETTO
 
@@ -914,8 +910,7 @@ TEST(TracingPerfetto) {
   auto tracing_session_ =
       perfetto::Tracing::NewTrace(perfetto::BackendType::kInProcessBackend);
   tracing_session_->Setup(perfetto_trace_config);
-  tracing_session_->Start();
-  TestDataSource::started_.Wait();
+  tracing_session_->StartBlocking();
 
   for (int i = 0; i < 15; i++) {
     TestDataSource::Trace([&](TestDataSource::TraceContext ctx) {
@@ -930,10 +925,7 @@ TEST(TracingPerfetto) {
       trace_event->set_thread_timestamp(123);
     });
   }
-  v8::base::Semaphore stopped_{0};
-  tracing_session_->SetOnStopCallback([&stopped_]() { stopped_.Signal(); });
-  tracing_session_->Stop();
-  stopped_.Wait();
+  tracing_session_->StopBlocking();
 
   std::ostringstream perfetto_json_stream_;