libchrome/base/debug/task_annotator.cc

// Copyright 2014 The Chromium 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 "base/debug/task_annotator.h"

#include "base/debug/alias.h"
#include "base/pending_task.h"
#include "base/trace_event/trace_event.h"
#include "base/tracked_objects.h"

namespace base {
namespace debug {

TaskAnnotator::TaskAnnotator() {
}

TaskAnnotator::~TaskAnnotator() {
}

void TaskAnnotator::DidQueueTask(const char* queue_function,
                                 const PendingTask& pending_task) {
  TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
                          queue_function,
                          TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
                          TRACE_EVENT_FLAG_FLOW_OUT);
}

void TaskAnnotator::RunTask(const char* queue_function,
                            const PendingTask& pending_task) {
  tracked_objects::TaskStopwatch stopwatch;
  stopwatch.Start();
  tracked_objects::Duration queue_duration =
      stopwatch.StartTime() - pending_task.EffectiveTimePosted();

  TRACE_EVENT_WITH_FLOW1(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
                          queue_function,
                          TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
                          TRACE_EVENT_FLAG_FLOW_IN,
                          "queue_duration",
                          queue_duration.InMilliseconds());

  // Before running the task, store the program counter where it was posted
  // and deliberately alias it to ensure it is on the stack if the task
  // crashes. Be careful not to assume that the variable itself will have the
  // expected value when displayed by the optimizer in an optimized build.
  // Look at a memory dump of the stack.
  const void* program_counter = pending_task.posted_from.program_counter();
  debug::Alias(&program_counter);

  pending_task.task.Run();

  stopwatch.Stop();
  tracked_objects::ThreadData::TallyRunOnNamedThreadIfTracking(
      pending_task, stopwatch);
}

uint64_t TaskAnnotator::GetTaskTraceID(const PendingTask& task) const {
  return (static_cast<uint64_t>(task.sequence_num) << 32) |
         ((static_cast<uint64_t>(reinterpret_cast<intptr_t>(this)) << 32) >>
          32);
}

}  // namespace debug
}  // namespace base