blob: 382bb3950b9cc778775b70590234677cdcffc548 [file] [log] [blame]
// 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 <array>
#include "base/debug/activity_tracker.h"
#include "base/debug/alias.h"
#include "base/no_destructor.h"
#include "base/pending_task.h"
#include "base/threading/thread_local.h"
#include "base/trace_event/trace_event.h"
namespace base {
namespace debug {
namespace {
TaskAnnotator::ObserverForTesting* g_task_annotator_observer = nullptr;
// Returns the TLS slot that stores the PendingTask currently in progress on
// each thread. Used to allow creating a breadcrumb of program counters on the
// stack to help identify a task's origin in crashes.
ThreadLocalPointer<const PendingTask>* GetTLSForCurrentPendingTask() {
static NoDestructor<ThreadLocalPointer<const PendingTask>>
tls_for_current_pending_task;
return tls_for_current_pending_task.get();
}
} // namespace
TaskAnnotator::TaskAnnotator() = default;
TaskAnnotator::~TaskAnnotator() = default;
void TaskAnnotator::WillQueueTask(const char* queue_function,
PendingTask* pending_task) {
if (queue_function) {
TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
queue_function,
TRACE_ID_MANGLE(GetTaskTraceID(*pending_task)),
TRACE_EVENT_FLAG_FLOW_OUT);
}
DCHECK(!pending_task->task_backtrace[0])
<< "Task backtrace was already set, task posted twice??";
if (!pending_task->task_backtrace[0]) {
const PendingTask* parent_task = GetTLSForCurrentPendingTask()->Get();
if (parent_task) {
pending_task->task_backtrace[0] =
parent_task->posted_from.program_counter();
std::copy(parent_task->task_backtrace.begin(),
parent_task->task_backtrace.end() - 1,
pending_task->task_backtrace.begin() + 1);
}
}
}
void TaskAnnotator::RunTask(const char* queue_function,
PendingTask* pending_task) {
ScopedTaskRunActivity task_activity(*pending_task);
if (queue_function) {
TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
queue_function,
TRACE_ID_MANGLE(GetTaskTraceID(*pending_task)),
TRACE_EVENT_FLAG_FLOW_IN);
}
// Before running the task, store the task backtrace with the chain of
// PostTasks that resulted in this call 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.
static constexpr int kStackTaskTraceSnapshotSize =
std::tuple_size<decltype(pending_task->task_backtrace)>::value + 3;
std::array<const void*, kStackTaskTraceSnapshotSize> task_backtrace;
// Store a marker to locate |task_backtrace| content easily on a memory
// dump.
task_backtrace.front() = reinterpret_cast<void*>(0xefefefefefefefef);
task_backtrace.back() = reinterpret_cast<void*>(0xfefefefefefefefe);
task_backtrace[1] = pending_task->posted_from.program_counter();
std::copy(pending_task->task_backtrace.begin(),
pending_task->task_backtrace.end(), task_backtrace.begin() + 2);
debug::Alias(&task_backtrace);
ThreadLocalPointer<const PendingTask>* tls_for_current_pending_task =
GetTLSForCurrentPendingTask();
const PendingTask* previous_pending_task =
tls_for_current_pending_task->Get();
tls_for_current_pending_task->Set(pending_task);
if (g_task_annotator_observer)
g_task_annotator_observer->BeforeRunTask(pending_task);
std::move(pending_task->task).Run();
tls_for_current_pending_task->Set(previous_pending_task);
}
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);
}
// static
void TaskAnnotator::RegisterObserverForTesting(ObserverForTesting* observer) {
DCHECK(!g_task_annotator_observer);
g_task_annotator_observer = observer;
}
// static
void TaskAnnotator::ClearObserverForTesting() {
g_task_annotator_observer = nullptr;
}
} // namespace debug
} // namespace base