[tracing] The CPU profiler should only be enabled for specific modes of tracing

src/profiler/tracing-cpu-profiler.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/profiler/tracing-cpu-profiler.h"
 
 #include "src/profiler/cpu-profiler.h"
 #include "src/tracing/trace-event.h"
 #include "src/v8.h"
 
-#define PROFILER_TRACE_CATEGORY_ENABLED(cat) \
-  (*TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(cat)))
+#define PROFILER_TRACE_CATEGORY_ENABLED(cat, ret) \

[alph, 2017/02/09 18:23:56]

Don't think this macro makes sense now. You can just directly use
TRACE_EVENT_CATEGORY_GROUP_ENABLED in those remaining two places.

[ssid, 2017/02/10 01:47:41]

Done.

+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(cat), ret)
 
 namespace v8 {
 
 std::unique_ptr<TracingCpuProfiler> TracingCpuProfiler::Create(
     v8::Isolate* isolate) {
   return std::unique_ptr<TracingCpuProfiler>(
       new internal::TracingCpuProfilerImpl(
           reinterpret_cast<internal::Isolate*>(isolate)));
 }
 
 namespace internal {
 
 TracingCpuProfilerImpl::TracingCpuProfilerImpl(Isolate* isolate)
     : isolate_(isolate), profiling_enabled_(false) {
   // Make sure tracing system notices profiler categories.
-  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler");
-  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires");
+  TRACE_EVENT_WARMUP_CATEGORY(TRACE_DISABLED_BY_DEFAULT("v8.cpu_profiler"));
+  TRACE_EVENT_WARMUP_CATEGORY(
+      TRACE_DISABLED_BY_DEFAULT("v8.cpu_profiler.hires"));
   V8::GetCurrentPlatform()->AddTraceStateObserver(this);
 }
 
 TracingCpuProfilerImpl::~TracingCpuProfilerImpl() {
   StopProfiling();
   V8::GetCurrentPlatform()->RemoveTraceStateObserver(this);
 }
 
 void TracingCpuProfilerImpl::OnTraceEnabled() {
-  if (!PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler")) return;
+  bool enabled;
+  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler", &enabled);
+  if (!enabled) return;
   profiling_enabled_ = true;
   isolate_->RequestInterrupt(
       [](v8::Isolate*, void* data) {
         reinterpret_cast<TracingCpuProfilerImpl*>(data)->StartProfiling();
       },
       this);
 }
 
 void TracingCpuProfilerImpl::OnTraceDisabled() {
   base::LockGuard<base::Mutex> lock(&mutex_);
   if (!profiling_enabled_) return;
   profiling_enabled_ = false;
   isolate_->RequestInterrupt(
       [](v8::Isolate*, void* data) {
         reinterpret_cast<TracingCpuProfilerImpl*>(data)->StopProfiling();
       },
       this);
 }
 
 void TracingCpuProfilerImpl::StartProfiling() {
   base::LockGuard<base::Mutex> lock(&mutex_);
   if (!profiling_enabled_ || profiler_) return;
-  int sampling_interval_us =
-      PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires") ? 100 : 1000;
+  bool enabled;
+  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires", &enabled);
+  int sampling_interval_us = enabled ? 100 : 1000;
   profiler_.reset(new CpuProfiler(isolate_));
   profiler_->set_sampling_interval(
       base::TimeDelta::FromMicroseconds(sampling_interval_us));
   profiler_->StartProfiling("", true);
 }
 
 void TracingCpuProfilerImpl::StopProfiling() {
   base::LockGuard<base::Mutex> lock(&mutex_);
   if (!profiler_) return;
   profiler_->StopProfiling("");
   profiler_.reset();
 }
 
 }  // namespace internal
 }  // namespace v8