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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "base/debug/task_annotator.h"
      6 
      7 #include <array>
      8 
      9 #include "base/debug/activity_tracker.h"
     10 #include "base/debug/alias.h"
     11 #include "base/pending_task.h"
     12 #include "base/trace_event/trace_event.h"
     13 #include "base/tracked_objects.h"
     14 
     15 namespace base {
     16 namespace debug {
     17 
     18 TaskAnnotator::TaskAnnotator() {
     19 }
     20 
     21 TaskAnnotator::~TaskAnnotator() {
     22 }
     23 
     24 void TaskAnnotator::DidQueueTask(const char* queue_function,
     25                                  const PendingTask& pending_task) {
     26   TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
     27                           queue_function,
     28                           TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
     29                           TRACE_EVENT_FLAG_FLOW_OUT);
     30 }
     31 
     32 void TaskAnnotator::RunTask(const char* queue_function,
     33                             PendingTask* pending_task) {
     34   ScopedTaskRunActivity task_activity(*pending_task);
     35 
     36   tracked_objects::TaskStopwatch stopwatch;
     37   stopwatch.Start();
     38   tracked_objects::Duration queue_duration =
     39       stopwatch.StartTime() - pending_task->EffectiveTimePosted();
     40 
     41   TRACE_EVENT_WITH_FLOW1(
     42       TRACE_DISABLED_BY_DEFAULT("toplevel.flow"), queue_function,
     43       TRACE_ID_MANGLE(GetTaskTraceID(*pending_task)), TRACE_EVENT_FLAG_FLOW_IN,
     44       "queue_duration", queue_duration.InMilliseconds());
     45 
     46   // Before running the task, store the task backtrace with the chain of
     47   // PostTasks that resulted in this call and deliberately alias it to ensure
     48   // it is on the stack if the task crashes. Be careful not to assume that the
     49   // variable itself will have the expected value when displayed by the
     50   // optimizer in an optimized build. Look at a memory dump of the stack.
     51   static constexpr int kStackTaskTraceSnapshotSize =
     52       std::tuple_size<decltype(pending_task->task_backtrace)>::value + 1;
     53   std::array<const void*, kStackTaskTraceSnapshotSize> task_backtrace;
     54   task_backtrace[0] = pending_task->posted_from.program_counter();
     55   std::copy(pending_task->task_backtrace.begin(),
     56             pending_task->task_backtrace.end(), task_backtrace.begin() + 1);
     57   debug::Alias(&task_backtrace);
     58 
     59   std::move(pending_task->task).Run();
     60 
     61   stopwatch.Stop();
     62   tracked_objects::ThreadData::TallyRunOnNamedThreadIfTracking(*pending_task,
     63                                                                stopwatch);
     64 }
     65 
     66 uint64_t TaskAnnotator::GetTaskTraceID(const PendingTask& task) const {
     67   return (static_cast<uint64_t>(task.sequence_num) << 32) |
     68          ((static_cast<uint64_t>(reinterpret_cast<intptr_t>(this)) << 32) >>
     69           32);
     70 }
     71 
     72 }  // namespace debug
     73 }  // namespace base
     74