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// Copyright (c) 2011 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/message_loop.h"
#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(ANDROID)
#include <gdk/gdk.h>
#include <gdk/gdkx.h>
#endif
#include <algorithm>
#include "base/compiler_specific.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/message_pump_default.h"
#include "base/metrics/histogram.h"
#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
#include "base/threading/thread_local.h"
#if defined(OS_MACOSX)
#include "base/message_pump_mac.h"
#endif
#if defined(OS_POSIX)
#include "base/message_pump_libevent.h"
#endif
#if defined(OS_POSIX) && !defined(OS_MACOSX)
#include "base/message_pump_glib.h"
#endif
#if defined(TOUCH_UI)
#include "base/message_pump_glib_x.h"
#endif
using base::TimeDelta;
using base::TimeTicks;
namespace {
// A lazily created thread local storage for quick access to a thread's message
// loop, if one exists. This should be safe and free of static constructors.
base::LazyInstance<base::ThreadLocalPointer<MessageLoop> > lazy_tls_ptr(
base::LINKER_INITIALIZED);
// Logical events for Histogram profiling. Run with -message-loop-histogrammer
// to get an accounting of messages and actions taken on each thread.
const int kTaskRunEvent = 0x1;
const int kTimerEvent = 0x2;
// Provide range of message IDs for use in histogramming and debug display.
const int kLeastNonZeroMessageId = 1;
const int kMaxMessageId = 1099;
const int kNumberOfDistinctMessagesDisplayed = 1100;
// Provide a macro that takes an expression (such as a constant, or macro
// constant) and creates a pair to initalize an array of pairs. In this case,
// our pair consists of the expressions value, and the "stringized" version
// of the expression (i.e., the exrpression put in quotes). For example, if
// we have:
// #define FOO 2
// #define BAR 5
// then the following:
// VALUE_TO_NUMBER_AND_NAME(FOO + BAR)
// will expand to:
// {7, "FOO + BAR"}
// We use the resulting array as an argument to our histogram, which reads the
// number as a bucket identifier, and proceeds to use the corresponding name
// in the pair (i.e., the quoted string) when printing out a histogram.
#define VALUE_TO_NUMBER_AND_NAME(name) {name, #name},
const base::LinearHistogram::DescriptionPair event_descriptions_[] = {
// Provide some pretty print capability in our histogram for our internal
// messages.
// A few events we handle (kindred to messages), and used to profile actions.
VALUE_TO_NUMBER_AND_NAME(kTaskRunEvent)
VALUE_TO_NUMBER_AND_NAME(kTimerEvent)
{-1, NULL} // The list must be null terminated, per API to histogram.
};
bool enable_histogrammer_ = false;
} // namespace
//------------------------------------------------------------------------------
#if defined(OS_WIN)
// Upon a SEH exception in this thread, it restores the original unhandled
// exception filter.
static int SEHFilter(LPTOP_LEVEL_EXCEPTION_FILTER old_filter) {
::SetUnhandledExceptionFilter(old_filter);
return EXCEPTION_CONTINUE_SEARCH;
}
// Retrieves a pointer to the current unhandled exception filter. There
// is no standalone getter method.
static LPTOP_LEVEL_EXCEPTION_FILTER GetTopSEHFilter() {
LPTOP_LEVEL_EXCEPTION_FILTER top_filter = NULL;
top_filter = ::SetUnhandledExceptionFilter(0);
::SetUnhandledExceptionFilter(top_filter);
return top_filter;
}
#endif // defined(OS_WIN)
//------------------------------------------------------------------------------
MessageLoop::TaskObserver::TaskObserver() {
}
MessageLoop::TaskObserver::~TaskObserver() {
}
MessageLoop::DestructionObserver::~DestructionObserver() {
}
//------------------------------------------------------------------------------
MessageLoop::MessageLoop(Type type)
: type_(type),
nestable_tasks_allowed_(true),
exception_restoration_(false),
message_histogram_(NULL),
state_(NULL),
#ifdef OS_WIN
os_modal_loop_(false),
#endif // OS_WIN
next_sequence_num_(0) {
DCHECK(!current()) << "should only have one message loop per thread";
lazy_tls_ptr.Pointer()->Set(this);
// TODO(rvargas): Get rid of the OS guards.
#if defined(OS_WIN)
#define MESSAGE_PUMP_UI new base::MessagePumpForUI()
#define MESSAGE_PUMP_IO new base::MessagePumpForIO()
#elif defined(OS_MACOSX)
#define MESSAGE_PUMP_UI base::MessagePumpMac::Create()
#define MESSAGE_PUMP_IO new base::MessagePumpLibevent()
#elif defined(ANDROID)
#define MESSAGE_PUMP_UI new base::MessagePumpDefault()
#define MESSAGE_PUMP_IO new base::MessagePumpLibevent()
#elif defined(TOUCH_UI)
#define MESSAGE_PUMP_UI new base::MessagePumpGlibX()
#define MESSAGE_PUMP_IO new base::MessagePumpLibevent()
#elif defined(OS_NACL)
// Currently NaCl doesn't have a UI or an IO MessageLoop.
// TODO(abarth): Figure out if we need these.
#define MESSAGE_PUMP_UI NULL
#define MESSAGE_PUMP_IO NULL
#elif defined(OS_POSIX) // POSIX but not MACOSX.
#define MESSAGE_PUMP_UI new base::MessagePumpForUI()
#define MESSAGE_PUMP_IO new base::MessagePumpLibevent()
#else
#error Not implemented
#endif
if (type_ == TYPE_UI) {
pump_ = MESSAGE_PUMP_UI;
} else if (type_ == TYPE_IO) {
pump_ = MESSAGE_PUMP_IO;
} else {
DCHECK_EQ(TYPE_DEFAULT, type_);
pump_ = new base::MessagePumpDefault();
}
}
MessageLoop::~MessageLoop() {
DCHECK_EQ(this, current());
DCHECK(!state_);
// Clean up any unprocessed tasks, but take care: deleting a task could
// result in the addition of more tasks (e.g., via DeleteSoon). We set a
// limit on the number of times we will allow a deleted task to generate more
// tasks. Normally, we should only pass through this loop once or twice. If
// we end up hitting the loop limit, then it is probably due to one task that
// is being stubborn. Inspect the queues to see who is left.
bool did_work;
for (int i = 0; i < 100; ++i) {
DeletePendingTasks();
ReloadWorkQueue();
// If we end up with empty queues, then break out of the loop.
did_work = DeletePendingTasks();
if (!did_work)
break;
}
DCHECK(!did_work);
// Let interested parties have one last shot at accessing this.
FOR_EACH_OBSERVER(DestructionObserver, destruction_observers_,
WillDestroyCurrentMessageLoop());
// OK, now make it so that no one can find us.
lazy_tls_ptr.Pointer()->Set(NULL);
}
// static
MessageLoop* MessageLoop::current() {
// TODO(darin): sadly, we cannot enable this yet since people call us even
// when they have no intention of using us.
// DCHECK(loop) << "Ouch, did you forget to initialize me?";
return lazy_tls_ptr.Pointer()->Get();
}
// static
void MessageLoop::EnableHistogrammer(bool enable) {
enable_histogrammer_ = enable;
}
void MessageLoop::AddDestructionObserver(
DestructionObserver* destruction_observer) {
DCHECK_EQ(this, current());
destruction_observers_.AddObserver(destruction_observer);
}
void MessageLoop::RemoveDestructionObserver(
DestructionObserver* destruction_observer) {
DCHECK_EQ(this, current());
destruction_observers_.RemoveObserver(destruction_observer);
}
void MessageLoop::PostTask(
const tracked_objects::Location& from_here, Task* task) {
PostTask_Helper(from_here, task, 0, true);
}
void MessageLoop::PostDelayedTask(
const tracked_objects::Location& from_here, Task* task, int64 delay_ms) {
PostTask_Helper(from_here, task, delay_ms, true);
}
void MessageLoop::PostNonNestableTask(
const tracked_objects::Location& from_here, Task* task) {
PostTask_Helper(from_here, task, 0, false);
}
void MessageLoop::PostNonNestableDelayedTask(
const tracked_objects::Location& from_here, Task* task, int64 delay_ms) {
PostTask_Helper(from_here, task, delay_ms, false);
}
void MessageLoop::Run() {
AutoRunState save_state(this);
RunHandler();
}
void MessageLoop::RunAllPending() {
AutoRunState save_state(this);
state_->quit_received = true; // Means run until we would otherwise block.
RunHandler();
}
void MessageLoop::Quit() {
DCHECK_EQ(this, current());
if (state_) {
state_->quit_received = true;
} else {
NOTREACHED() << "Must be inside Run to call Quit";
}
}
void MessageLoop::QuitNow() {
DCHECK_EQ(this, current());
if (state_) {
pump_->Quit();
} else {
NOTREACHED() << "Must be inside Run to call Quit";
}
}
void MessageLoop::SetNestableTasksAllowed(bool allowed) {
if (nestable_tasks_allowed_ != allowed) {
nestable_tasks_allowed_ = allowed;
if (!nestable_tasks_allowed_)
return;
// Start the native pump if we are not already pumping.
pump_->ScheduleWork();
}
}
bool MessageLoop::NestableTasksAllowed() const {
return nestable_tasks_allowed_;
}
bool MessageLoop::IsNested() {
return state_->run_depth > 1;
}
void MessageLoop::AddTaskObserver(TaskObserver* task_observer) {
DCHECK_EQ(this, current());
task_observers_.AddObserver(task_observer);
}
void MessageLoop::RemoveTaskObserver(TaskObserver* task_observer) {
DCHECK_EQ(this, current());
task_observers_.RemoveObserver(task_observer);
}
void MessageLoop::AssertIdle() const {
// We only check |incoming_queue_|, since we don't want to lock |work_queue_|.
base::AutoLock lock(incoming_queue_lock_);
DCHECK(incoming_queue_.empty());
}
//------------------------------------------------------------------------------
// Runs the loop in two different SEH modes:
// enable_SEH_restoration_ = false : any unhandled exception goes to the last
// one that calls SetUnhandledExceptionFilter().
// enable_SEH_restoration_ = true : any unhandled exception goes to the filter
// that was existed before the loop was run.
void MessageLoop::RunHandler() {
#if defined(OS_WIN)
if (exception_restoration_) {
RunInternalInSEHFrame();
return;
}
#endif
RunInternal();
}
#if defined(OS_WIN)
__declspec(noinline) void MessageLoop::RunInternalInSEHFrame() {
LPTOP_LEVEL_EXCEPTION_FILTER current_filter = GetTopSEHFilter();
__try {
RunInternal();
} __except(SEHFilter(current_filter)) {
}
return;
}
#endif
void MessageLoop::RunInternal() {
DCHECK_EQ(this, current());
#ifndef ANDROID
StartHistogrammer();
#endif
#if !defined(OS_MACOSX)
if (state_->dispatcher && type() == TYPE_UI) {
static_cast<base::MessagePumpForUI*>(pump_.get())->
RunWithDispatcher(this, state_->dispatcher);
return;
}
#endif
pump_->Run(this);
}
bool MessageLoop::ProcessNextDelayedNonNestableTask() {
if (state_->run_depth != 1)
return false;
if (deferred_non_nestable_work_queue_.empty())
return false;
Task* task = deferred_non_nestable_work_queue_.front().task;
deferred_non_nestable_work_queue_.pop();
RunTask(task);
return true;
}
void MessageLoop::RunTask(Task* task) {
DCHECK(nestable_tasks_allowed_);
// Execute the task and assume the worst: It is probably not reentrant.
nestable_tasks_allowed_ = false;
HistogramEvent(kTaskRunEvent);
FOR_EACH_OBSERVER(TaskObserver, task_observers_,
WillProcessTask(task));
task->Run();
FOR_EACH_OBSERVER(TaskObserver, task_observers_, DidProcessTask(task));
delete task;
nestable_tasks_allowed_ = true;
}
bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
if (pending_task.nestable || state_->run_depth == 1) {
RunTask(pending_task.task);
// Show that we ran a task (Note: a new one might arrive as a
// consequence!).
return true;
}
// We couldn't run the task now because we're in a nested message loop
// and the task isn't nestable.
deferred_non_nestable_work_queue_.push(pending_task);
return false;
}
void MessageLoop::AddToDelayedWorkQueue(const PendingTask& pending_task) {
// Move to the delayed work queue. Initialize the sequence number
// before inserting into the delayed_work_queue_. The sequence number
// is used to faciliate FIFO sorting when two tasks have the same
// delayed_run_time value.
PendingTask new_pending_task(pending_task);
new_pending_task.sequence_num = next_sequence_num_++;
delayed_work_queue_.push(new_pending_task);
}
void MessageLoop::ReloadWorkQueue() {
// We can improve performance of our loading tasks from incoming_queue_ to
// work_queue_ by waiting until the last minute (work_queue_ is empty) to
// load. That reduces the number of locks-per-task significantly when our
// queues get large.
if (!work_queue_.empty())
return; // Wait till we *really* need to lock and load.
// Acquire all we can from the inter-thread queue with one lock acquisition.
{
base::AutoLock lock(incoming_queue_lock_);
if (incoming_queue_.empty())
return;
incoming_queue_.Swap(&work_queue_); // Constant time
DCHECK(incoming_queue_.empty());
}
}
bool MessageLoop::DeletePendingTasks() {
bool did_work = !work_queue_.empty();
while (!work_queue_.empty()) {
PendingTask pending_task = work_queue_.front();
work_queue_.pop();
if (!pending_task.delayed_run_time.is_null()) {
// We want to delete delayed tasks in the same order in which they would
// normally be deleted in case of any funny dependencies between delayed
// tasks.
AddToDelayedWorkQueue(pending_task);
} else {
// TODO(darin): Delete all tasks once it is safe to do so.
// Until it is totally safe, just do it when running Purify or
// Valgrind.
#if defined(PURIFY) || defined(USE_HEAPCHECKER)
delete pending_task.task;
#else
if (RunningOnValgrind())
delete pending_task.task;
#endif // defined(OS_POSIX)
}
}
did_work |= !deferred_non_nestable_work_queue_.empty();
while (!deferred_non_nestable_work_queue_.empty()) {
// TODO(darin): Delete all tasks once it is safe to do so.
// Until it is totaly safe, only delete them under Purify and Valgrind.
Task* task = NULL;
#if defined(PURIFY) || defined(USE_HEAPCHECKER)
task = deferred_non_nestable_work_queue_.front().task;
#else
if (RunningOnValgrind())
task = deferred_non_nestable_work_queue_.front().task;
#endif
deferred_non_nestable_work_queue_.pop();
if (task)
delete task;
}
did_work |= !delayed_work_queue_.empty();
while (!delayed_work_queue_.empty()) {
Task* task = delayed_work_queue_.top().task;
delayed_work_queue_.pop();
delete task;
}
return did_work;
}
// Possibly called on a background thread!
void MessageLoop::PostTask_Helper(
const tracked_objects::Location& from_here, Task* task, int64 delay_ms,
bool nestable) {
task->SetBirthPlace(from_here);
PendingTask pending_task(task, nestable);
if (delay_ms > 0) {
pending_task.delayed_run_time =
TimeTicks::Now() + TimeDelta::FromMilliseconds(delay_ms);
#if defined(OS_WIN)
if (high_resolution_timer_expiration_.is_null()) {
// Windows timers are granular to 15.6ms. If we only set high-res
// timers for those under 15.6ms, then a 18ms timer ticks at ~32ms,
// which as a percentage is pretty inaccurate. So enable high
// res timers for any timer which is within 2x of the granularity.
// This is a tradeoff between accuracy and power management.
bool needs_high_res_timers =
delay_ms < (2 * base::Time::kMinLowResolutionThresholdMs);
if (needs_high_res_timers) {
base::Time::ActivateHighResolutionTimer(true);
high_resolution_timer_expiration_ = TimeTicks::Now() +
TimeDelta::FromMilliseconds(kHighResolutionTimerModeLeaseTimeMs);
}
}
#endif
} else {
DCHECK_EQ(delay_ms, 0) << "delay should not be negative";
}
#if defined(OS_WIN)
if (!high_resolution_timer_expiration_.is_null()) {
if (TimeTicks::Now() > high_resolution_timer_expiration_) {
base::Time::ActivateHighResolutionTimer(false);
high_resolution_timer_expiration_ = TimeTicks();
}
}
#endif
// Warning: Don't try to short-circuit, and handle this thread's tasks more
// directly, as it could starve handling of foreign threads. Put every task
// into this queue.
scoped_refptr<base::MessagePump> pump;
{
base::AutoLock locked(incoming_queue_lock_);
bool was_empty = incoming_queue_.empty();
incoming_queue_.push(pending_task);
if (!was_empty)
return; // Someone else should have started the sub-pump.
pump = pump_;
}
// Since the incoming_queue_ may contain a task that destroys this message
// loop, we cannot exit incoming_queue_lock_ until we are done with |this|.
// We use a stack-based reference to the message pump so that we can call
// ScheduleWork outside of incoming_queue_lock_.
pump->ScheduleWork();
}
//------------------------------------------------------------------------------
// Method and data for histogramming events and actions taken by each instance
// on each thread.
void MessageLoop::StartHistogrammer() {
if (enable_histogrammer_ && !message_histogram_
&& base::StatisticsRecorder::IsActive()) {
DCHECK(!thread_name_.empty());
message_histogram_ = base::LinearHistogram::FactoryGet(
"MsgLoop:" + thread_name_,
kLeastNonZeroMessageId, kMaxMessageId,
kNumberOfDistinctMessagesDisplayed,
message_histogram_->kHexRangePrintingFlag);
message_histogram_->SetRangeDescriptions(event_descriptions_);
}
}
void MessageLoop::HistogramEvent(int event) {
if (message_histogram_)
message_histogram_->Add(event);
}
bool MessageLoop::DoWork() {
if (!nestable_tasks_allowed_) {
// Task can't be executed right now.
return false;
}
for (;;) {
ReloadWorkQueue();
if (work_queue_.empty())
break;
// Execute oldest task.
do {
PendingTask pending_task = work_queue_.front();
work_queue_.pop();
if (!pending_task.delayed_run_time.is_null()) {
AddToDelayedWorkQueue(pending_task);
// If we changed the topmost task, then it is time to re-schedule.
if (delayed_work_queue_.top().task == pending_task.task)
pump_->ScheduleDelayedWork(pending_task.delayed_run_time);
} else {
if (DeferOrRunPendingTask(pending_task))
return true;
}
} while (!work_queue_.empty());
}
// Nothing happened.
return false;
}
bool MessageLoop::DoDelayedWork(base::TimeTicks* next_delayed_work_time) {
if (!nestable_tasks_allowed_ || delayed_work_queue_.empty()) {
recent_time_ = *next_delayed_work_time = TimeTicks();
return false;
}
// When we "fall behind," there will be a lot of tasks in the delayed work
// queue that are ready to run. To increase efficiency when we fall behind,
// we will only call Time::Now() intermittently, and then process all tasks
// that are ready to run before calling it again. As a result, the more we
// fall behind (and have a lot of ready-to-run delayed tasks), the more
// efficient we'll be at handling the tasks.
TimeTicks next_run_time = delayed_work_queue_.top().delayed_run_time;
if (next_run_time > recent_time_) {
recent_time_ = TimeTicks::Now(); // Get a better view of Now();
if (next_run_time > recent_time_) {
*next_delayed_work_time = next_run_time;
return false;
}
}
PendingTask pending_task = delayed_work_queue_.top();
delayed_work_queue_.pop();
if (!delayed_work_queue_.empty())
*next_delayed_work_time = delayed_work_queue_.top().delayed_run_time;
return DeferOrRunPendingTask(pending_task);
}
bool MessageLoop::DoIdleWork() {
if (ProcessNextDelayedNonNestableTask())
return true;
if (state_->quit_received)
pump_->Quit();
return false;
}
//------------------------------------------------------------------------------
// MessageLoop::AutoRunState
MessageLoop::AutoRunState::AutoRunState(MessageLoop* loop) : loop_(loop) {
// Make the loop reference us.
previous_state_ = loop_->state_;
if (previous_state_) {
run_depth = previous_state_->run_depth + 1;
} else {
run_depth = 1;
}
loop_->state_ = this;
// Initialize the other fields:
quit_received = false;
#if !defined(OS_MACOSX)
dispatcher = NULL;
#endif
}
MessageLoop::AutoRunState::~AutoRunState() {
loop_->state_ = previous_state_;
}
//------------------------------------------------------------------------------
// MessageLoop::PendingTask
bool MessageLoop::PendingTask::operator<(const PendingTask& other) const {
// Since the top of a priority queue is defined as the "greatest" element, we
// need to invert the comparison here. We want the smaller time to be at the
// top of the heap.
if (delayed_run_time < other.delayed_run_time)
return false;
if (delayed_run_time > other.delayed_run_time)
return true;
// If the times happen to match, then we use the sequence number to decide.
// Compare the difference to support integer roll-over.
return (sequence_num - other.sequence_num) > 0;
}
//------------------------------------------------------------------------------
// MessageLoopForUI
#if defined(OS_WIN)
void MessageLoopForUI::DidProcessMessage(const MSG& message) {
pump_win()->DidProcessMessage(message);
}
#endif // defined(OS_WIN)
#if defined(USE_X11)
Display* MessageLoopForUI::GetDisplay() {
return gdk_x11_get_default_xdisplay();
}
#endif // defined(USE_X11)
#if !defined(OS_MACOSX) && !defined(OS_NACL) && !defined(ANDROID)
void MessageLoopForUI::AddObserver(Observer* observer) {
pump_ui()->AddObserver(observer);
}
void MessageLoopForUI::RemoveObserver(Observer* observer) {
pump_ui()->RemoveObserver(observer);
}
void MessageLoopForUI::Run(Dispatcher* dispatcher) {
AutoRunState save_state(this);
state_->dispatcher = dispatcher;
RunHandler();
}
#endif // !defined(OS_MACOSX) && !defined(OS_NACL)
//------------------------------------------------------------------------------
// MessageLoopForIO
#if defined(OS_WIN)
void MessageLoopForIO::RegisterIOHandler(HANDLE file, IOHandler* handler) {
pump_io()->RegisterIOHandler(file, handler);
}
bool MessageLoopForIO::WaitForIOCompletion(DWORD timeout, IOHandler* filter) {
return pump_io()->WaitForIOCompletion(timeout, filter);
}
#elif defined(OS_POSIX) && !defined(OS_NACL)
bool MessageLoopForIO::WatchFileDescriptor(int fd,
bool persistent,
Mode mode,
FileDescriptorWatcher *controller,
Watcher *delegate) {
return pump_libevent()->WatchFileDescriptor(
fd,
persistent,
static_cast<base::MessagePumpLibevent::Mode>(mode),
controller,
delegate);
}
#endif
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