Record async "task backtraces"
Places a small array in PendingTask that records the past 4 PostTasks
that result in this task being run. In essence, it creates a backtrace
of the asynchronous call stack resulting in this task being run.
This array is copied onto the stack during execution so that it is
available in crash dumps.
BUG=690197
Review-Url: https://codereview.chromium.org/1044413002
Cr-Commit-Position: refs/heads/master@{#449471}
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 99017c74..805b7a1d3 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -2019,6 +2019,7 @@
"optional_unittest.cc",
"os_compat_android_unittest.cc",
"path_service_unittest.cc",
+ "pending_task_unittest.cc",
"pickle_unittest.cc",
"posix/file_descriptor_shuffle_unittest.cc",
"posix/unix_domain_socket_linux_unittest.cc",
diff --git a/base/debug/task_annotator.cc b/base/debug/task_annotator.cc
index 437d69a7..46969f2 100644
--- a/base/debug/task_annotator.cc
+++ b/base/debug/task_annotator.cc
@@ -4,6 +4,8 @@
#include "base/debug/task_annotator.h"
+#include <array>
+
#include "base/debug/activity_tracker.h"
#include "base/debug/alias.h"
#include "base/pending_task.h"
@@ -41,13 +43,18 @@
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);
+ // 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 + 1;
+ std::array<const void*, kStackTaskTraceSnapshotSize> task_backtrace;
+ task_backtrace[0] = pending_task->posted_from.program_counter();
+ std::copy(pending_task->task_backtrace.begin(),
+ pending_task->task_backtrace.end(), task_backtrace.begin() + 1);
+ debug::Alias(&task_backtrace);
std::move(pending_task->task).Run();
diff --git a/base/message_loop/incoming_task_queue.cc b/base/message_loop/incoming_task_queue.cc
index c32afda1..c7faa9a 100644
--- a/base/message_loop/incoming_task_queue.cc
+++ b/base/message_loop/incoming_task_queue.cc
@@ -67,8 +67,8 @@
<< "Requesting super-long task delay period of " << delay.InSeconds()
<< " seconds from here: " << from_here.ToString();
- PendingTask pending_task(
- from_here, task, CalculateDelayedRuntime(delay), nestable);
+ PendingTask pending_task(from_here, task, CalculateDelayedRuntime(delay),
+ nestable);
#if defined(OS_WIN)
// We consider the task needs a high resolution timer if the delay is
// more than 0 and less than 32ms. This caps the relative error to
diff --git a/base/message_loop/message_loop.cc b/base/message_loop/message_loop.cc
index 72185a8..60df713 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -320,7 +320,8 @@
#endif
nestable_tasks_allowed_(true),
pump_factory_(pump_factory),
- run_loop_(NULL),
+ run_loop_(nullptr),
+ current_pending_task_(nullptr),
incoming_task_queue_(new internal::IncomingTaskQueue(this)),
unbound_task_runner_(
new internal::MessageLoopTaskRunner(incoming_task_queue_)),
@@ -403,6 +404,7 @@
void MessageLoop::RunTask(PendingTask* pending_task) {
DCHECK(nestable_tasks_allowed_);
+ current_pending_task_ = pending_task;
#if defined(OS_WIN)
if (pending_task->is_high_res) {
@@ -423,6 +425,8 @@
observer.DidProcessTask(*pending_task);
nestable_tasks_allowed_ = true;
+
+ current_pending_task_ = nullptr;
}
bool MessageLoop::DeferOrRunPendingTask(PendingTask pending_task) {
diff --git a/base/message_loop/message_loop.h b/base/message_loop/message_loop.h
index 91a7b1d3..8417ce49c 100644
--- a/base/message_loop/message_loop.h
+++ b/base/message_loop/message_loop.h
@@ -346,11 +346,13 @@
void BindToCurrentThread();
private:
- friend class RunLoop;
friend class internal::IncomingTaskQueue;
+ friend class RunLoop;
friend class ScheduleWorkTest;
friend class Thread;
+ friend struct PendingTask;
FRIEND_TEST_ALL_PREFIXES(MessageLoopTest, DeleteUnboundLoop);
+ friend class PendingTaskTest;
// Creates a MessageLoop without binding to a thread.
// If |type| is TYPE_CUSTOM non-null |pump_factory| must be also given
@@ -450,6 +452,13 @@
debug::TaskAnnotator task_annotator_;
+ // Used to allow creating a breadcrumb of program counters in PostTask.
+ // This variable is only initialized while a task is being executed and is
+ // meant only to store context for creating a backtrace breadcrumb. Do not
+ // attach other semantics to it without thinking through the use caes
+ // thoroughly.
+ const PendingTask* current_pending_task_;
+
scoped_refptr<internal::IncomingTaskQueue> incoming_task_queue_;
// A task runner which we haven't bound to a thread yet.
diff --git a/base/pending_task.cc b/base/pending_task.cc
index cca9ebf..b2f95b4 100644
--- a/base/pending_task.cc
+++ b/base/pending_task.cc
@@ -4,18 +4,14 @@
#include "base/pending_task.h"
+#include "base/message_loop/message_loop.h"
#include "base/tracked_objects.h"
namespace base {
PendingTask::PendingTask(const tracked_objects::Location& posted_from,
OnceClosure task)
- : base::TrackingInfo(posted_from, TimeTicks()),
- task(std::move(task)),
- posted_from(posted_from),
- sequence_num(0),
- nestable(true),
- is_high_res(false) {}
+ : PendingTask(posted_from, std::move(task), TimeTicks(), true) {}
PendingTask::PendingTask(const tracked_objects::Location& posted_from,
OnceClosure task,
@@ -26,7 +22,19 @@
posted_from(posted_from),
sequence_num(0),
nestable(nestable),
- is_high_res(false) {}
+ is_high_res(false) {
+ const PendingTask* parent_task =
+ MessageLoop::current() ? MessageLoop::current()->current_pending_task_
+ : nullptr;
+ if (parent_task) {
+ task_backtrace[0] = parent_task->posted_from.program_counter();
+ std::copy(parent_task->task_backtrace.begin(),
+ parent_task->task_backtrace.end() - 1,
+ task_backtrace.begin() + 1);
+ } else {
+ task_backtrace.fill(nullptr);
+ }
+}
PendingTask::PendingTask(PendingTask&& other) = default;
diff --git a/base/pending_task.h b/base/pending_task.h
index a55fa518..7f3fccd8 100644
--- a/base/pending_task.h
+++ b/base/pending_task.h
@@ -5,6 +5,7 @@
#ifndef BASE_PENDING_TASK_H_
#define BASE_PENDING_TASK_H_
+#include <array>
#include <queue>
#include "base/base_export.h"
@@ -37,6 +38,9 @@
// The site this PendingTask was posted from.
tracked_objects::Location posted_from;
+ // Task backtrace.
+ std::array<const void*, 4> task_backtrace;
+
// Secondary sort key for run time.
int sequence_num;
diff --git a/base/pending_task_unittest.cc b/base/pending_task_unittest.cc
new file mode 100644
index 0000000..8d52daa9
--- /dev/null
+++ b/base/pending_task_unittest.cc
@@ -0,0 +1,169 @@
+// Copyright (c) 2017 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/pending_task.h"
+
+#include <vector>
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/strings/stringprintf.h"
+#include "base/threading/thread.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+class PendingTaskTest : public ::testing::Test {
+ public:
+ PendingTaskTest() = default;
+
+ ~PendingTaskTest() override = default;
+
+ protected:
+ using ExpectedTrace = std::vector<const void*>;
+
+ static void VerifyTraceAndPost(
+ const scoped_refptr<TaskRunner>& task_runner,
+ const tracked_objects::Location& posted_from,
+ const tracked_objects::Location& next_from_here,
+ const std::vector<const void*>& expected_trace,
+ Closure task) {
+ SCOPED_TRACE(StringPrintf("Callback Depth: %zu", expected_trace.size()));
+
+ // Beyond depth + 1, the trace is nonsensical because there haven't been
+ // enough nested tasks called.
+ const PendingTask* current_pending_task =
+ MessageLoop::current()->current_pending_task_;
+ size_t window = std::min(current_pending_task->task_backtrace.size(),
+ expected_trace.size());
+
+ EXPECT_EQ(posted_from,
+ MessageLoop::current()->current_pending_task_->posted_from);
+ for (size_t i = 0; i < window; i++) {
+ SCOPED_TRACE(StringPrintf("Trace frame: %zu", i));
+ EXPECT_EQ(expected_trace[i], current_pending_task->task_backtrace[i]);
+ }
+ task_runner->PostTask(next_from_here, std::move(task));
+ }
+
+ static void RunTwo(Closure c1, Closure c2) {
+ c1.Run();
+ c2.Run();
+ }
+};
+
+// Ensure the task backtrace populates correctly.
+TEST_F(PendingTaskTest, SingleThreadedSimple) {
+ MessageLoop loop;
+ const tracked_objects::Location& location0 = FROM_HERE;
+ const tracked_objects::Location& location1 = FROM_HERE;
+ const tracked_objects::Location& location2 = FROM_HERE;
+ const tracked_objects::Location& location3 = FROM_HERE;
+ const tracked_objects::Location& location4 = FROM_HERE;
+ const tracked_objects::Location& location5 = FROM_HERE;
+
+ Closure task5 = Bind(
+ &PendingTaskTest::VerifyTraceAndPost, loop.task_runner(), location4,
+ location5,
+ ExpectedTrace({location3.program_counter(), location2.program_counter(),
+ location1.program_counter(), location0.program_counter()}),
+ Bind(&DoNothing));
+ Closure task4 = Bind(
+ &PendingTaskTest::VerifyTraceAndPost, loop.task_runner(), location3,
+ location4,
+ ExpectedTrace({location2.program_counter(), location1.program_counter(),
+ location0.program_counter(), nullptr}),
+ task5);
+ Closure task3 = Bind(
+ &PendingTaskTest::VerifyTraceAndPost, loop.task_runner(), location2,
+ location3, ExpectedTrace({location1.program_counter(),
+ location0.program_counter(), nullptr, nullptr}),
+ task4);
+ Closure task2 =
+ Bind(&PendingTaskTest::VerifyTraceAndPost, loop.task_runner(), location1,
+ location2, ExpectedTrace({location0.program_counter()}), task3);
+ Closure task1 = Bind(&PendingTaskTest::VerifyTraceAndPost, loop.task_runner(),
+ location0, location1, ExpectedTrace({}), task2);
+
+ loop.task_runner()->PostTask(location0, task1);
+
+ RunLoop().RunUntilIdle();
+}
+
+// Post a task onto another thread. Ensure on the other thread, it has the
+// right stack trace.
+TEST_F(PendingTaskTest, MultipleThreads) {
+ MessageLoop loop; // Implicitly "thread a."
+ Thread thread_b("pt_test_b");
+ Thread thread_c("pt_test_c");
+ thread_b.StartAndWaitForTesting();
+ thread_c.StartAndWaitForTesting();
+
+ const tracked_objects::Location& location_a0 = FROM_HERE;
+ const tracked_objects::Location& location_a1 = FROM_HERE;
+ const tracked_objects::Location& location_a2 = FROM_HERE;
+ const tracked_objects::Location& location_a3 = FROM_HERE;
+
+ const tracked_objects::Location& location_b0 = FROM_HERE;
+ const tracked_objects::Location& location_b1 = FROM_HERE;
+
+ const tracked_objects::Location& location_c0 = FROM_HERE;
+
+ // On thread c, post a task back to thread a that verifies its trace
+ // and terminates after one more self-post.
+ Closure task_a2 =
+ Bind(&PendingTaskTest::VerifyTraceAndPost, loop.task_runner(),
+ location_a2, location_a3,
+ ExpectedTrace(
+ {location_c0.program_counter(), location_b0.program_counter(),
+ location_a1.program_counter(), location_a0.program_counter()}),
+ Bind(&DoNothing));
+ Closure task_c0 = Bind(&PendingTaskTest::VerifyTraceAndPost,
+ loop.task_runner(), location_c0, location_a2,
+ ExpectedTrace({location_b0.program_counter(),
+ location_a1.program_counter(),
+ location_a0.program_counter()}),
+ task_a2);
+
+ // On thread b run two tasks that conceptually come from the same location
+ // (managed via RunTwo().) One will post back to thread b and another will
+ // post to thread c to test spawning multiple tasks on different message
+ // loops. The task posted to thread c will not get location b1 whereas the
+ // one posted back to thread b will.
+ Closure task_b0_fork =
+ Bind(&PendingTaskTest::VerifyTraceAndPost,
+ thread_c.message_loop()->task_runner(), location_b0, location_c0,
+ ExpectedTrace({location_a1.program_counter(),
+ location_a0.program_counter(), nullptr}),
+ task_c0);
+ Closure task_b0_local =
+ Bind(&PendingTaskTest::VerifyTraceAndPost,
+ thread_b.message_loop()->task_runner(), location_b0, location_b1,
+ ExpectedTrace({location_a1.program_counter(),
+ location_a0.program_counter(), nullptr}),
+ Bind(&DoNothing));
+
+ // Push one frame onto the stack in thread a then pass to thread b.
+ Closure task_a1 =
+ Bind(&PendingTaskTest::VerifyTraceAndPost,
+ thread_b.message_loop()->task_runner(), location_a1, location_b0,
+ ExpectedTrace({location_a0.program_counter(), nullptr}),
+ Bind(&PendingTaskTest::RunTwo, task_b0_local, task_b0_fork));
+ Closure task_a0 =
+ Bind(&PendingTaskTest::VerifyTraceAndPost, loop.task_runner(),
+ location_a0, location_a1, ExpectedTrace({nullptr}), task_a1);
+
+ loop.task_runner()->PostTask(location_a0, task_a0);
+
+ RunLoop().RunUntilIdle();
+
+ thread_b.FlushForTesting();
+ thread_b.Stop();
+
+ thread_c.FlushForTesting();
+ thread_c.Stop();
+}
+
+} // namespace base
