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125 lines
4.5 KiB
125 lines
4.5 KiB
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/debug/task_annotator.h"
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#include <array>
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#include "base/debug/activity_tracker.h"
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#include "base/debug/alias.h"
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#include "base/no_destructor.h"
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#include "base/pending_task.h"
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#include "base/threading/thread_local.h"
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#include "base/trace_event/trace_event.h"
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namespace base {
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namespace debug {
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namespace {
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TaskAnnotator::ObserverForTesting* g_task_annotator_observer = nullptr;
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// Returns the TLS slot that stores the PendingTask currently in progress on
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// each thread. Used to allow creating a breadcrumb of program counters on the
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// stack to help identify a task's origin in crashes.
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ThreadLocalPointer<const PendingTask>* GetTLSForCurrentPendingTask() {
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static NoDestructor<ThreadLocalPointer<const PendingTask>>
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tls_for_current_pending_task;
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return tls_for_current_pending_task.get();
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}
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} // namespace
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TaskAnnotator::TaskAnnotator() = default;
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TaskAnnotator::~TaskAnnotator() = default;
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void TaskAnnotator::WillQueueTask(const char* queue_function,
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PendingTask* pending_task) {
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if (queue_function) {
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TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
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queue_function,
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TRACE_ID_MANGLE(GetTaskTraceID(*pending_task)),
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TRACE_EVENT_FLAG_FLOW_OUT);
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}
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// TODO(https://crbug.com/826902): Fix callers that invoke WillQueueTask()
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// twice for the same PendingTask.
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// DCHECK(!pending_task.task_backtrace[0])
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// << "Task backtrace was already set, task posted twice??";
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if (!pending_task->task_backtrace[0]) {
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const PendingTask* parent_task = GetTLSForCurrentPendingTask()->Get();
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if (parent_task) {
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pending_task->task_backtrace[0] =
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parent_task->posted_from.program_counter();
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std::copy(parent_task->task_backtrace.begin(),
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parent_task->task_backtrace.end() - 1,
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pending_task->task_backtrace.begin() + 1);
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}
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}
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}
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void TaskAnnotator::RunTask(const char* queue_function,
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PendingTask* pending_task) {
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ScopedTaskRunActivity task_activity(*pending_task);
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if (queue_function) {
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TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
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queue_function,
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TRACE_ID_MANGLE(GetTaskTraceID(*pending_task)),
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TRACE_EVENT_FLAG_FLOW_IN);
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}
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// Before running the task, store the task backtrace with the chain of
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// PostTasks that resulted in this call and deliberately alias it to ensure
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// it is on the stack if the task crashes. Be careful not to assume that the
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// variable itself will have the expected value when displayed by the
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// optimizer in an optimized build. Look at a memory dump of the stack.
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static constexpr int kStackTaskTraceSnapshotSize =
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std::tuple_size<decltype(pending_task->task_backtrace)>::value + 3;
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std::array<const void*, kStackTaskTraceSnapshotSize> task_backtrace;
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// Store a marker to locate |task_backtrace| content easily on a memory
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// dump.
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task_backtrace.front() = reinterpret_cast<void*>(0xefefefefefefefef);
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task_backtrace.back() = reinterpret_cast<void*>(0xfefefefefefefefe);
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task_backtrace[1] = pending_task->posted_from.program_counter();
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std::copy(pending_task->task_backtrace.begin(),
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pending_task->task_backtrace.end(), task_backtrace.begin() + 2);
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debug::Alias(&task_backtrace);
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ThreadLocalPointer<const PendingTask>* tls_for_current_pending_task =
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GetTLSForCurrentPendingTask();
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const PendingTask* previous_pending_task =
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tls_for_current_pending_task->Get();
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tls_for_current_pending_task->Set(pending_task);
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if (g_task_annotator_observer)
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g_task_annotator_observer->BeforeRunTask(pending_task);
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std::move(pending_task->task).Run();
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tls_for_current_pending_task->Set(previous_pending_task);
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}
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uint64_t TaskAnnotator::GetTaskTraceID(const PendingTask& task) const {
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return (static_cast<uint64_t>(task.sequence_num) << 32) |
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((static_cast<uint64_t>(reinterpret_cast<intptr_t>(this)) << 32) >>
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32);
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}
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// static
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void TaskAnnotator::RegisterObserverForTesting(ObserverForTesting* observer) {
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DCHECK(!g_task_annotator_observer);
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g_task_annotator_observer = observer;
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}
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// static
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void TaskAnnotator::ClearObserverForTesting() {
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g_task_annotator_observer = nullptr;
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}
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} // namespace debug
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} // namespace base
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