blob: 9b4d1a2308cebf8348881f7c27f2a33252fa3c72 [file] [log] [blame]
/*
* Copyright 2016 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "webrtc/rtc_base/task_queue.h"
#include <mmsystem.h>
#include <string.h>
#include <algorithm>
#include <queue>
#include "webrtc/rtc_base/arraysize.h"
#include "webrtc/rtc_base/checks.h"
#include "webrtc/rtc_base/logging.h"
#include "webrtc/rtc_base/safe_conversions.h"
#include "webrtc/rtc_base/timeutils.h"
namespace rtc {
namespace {
#define WM_RUN_TASK WM_USER + 1
#define WM_QUEUE_DELAYED_TASK WM_USER + 2
using Priority = TaskQueue::Priority;
DWORD g_queue_ptr_tls = 0;
BOOL CALLBACK InitializeTls(PINIT_ONCE init_once, void* param, void** context) {
g_queue_ptr_tls = TlsAlloc();
return TRUE;
}
DWORD GetQueuePtrTls() {
static INIT_ONCE init_once = INIT_ONCE_STATIC_INIT;
::InitOnceExecuteOnce(&init_once, InitializeTls, nullptr, nullptr);
return g_queue_ptr_tls;
}
struct ThreadStartupData {
Event* started;
void* thread_context;
};
void CALLBACK InitializeQueueThread(ULONG_PTR param) {
MSG msg;
::PeekMessage(&msg, nullptr, WM_USER, WM_USER, PM_NOREMOVE);
ThreadStartupData* data = reinterpret_cast<ThreadStartupData*>(param);
::TlsSetValue(GetQueuePtrTls(), data->thread_context);
data->started->Set();
}
ThreadPriority TaskQueuePriorityToThreadPriority(Priority priority) {
switch (priority) {
case Priority::HIGH:
return kRealtimePriority;
case Priority::LOW:
return kLowPriority;
case Priority::NORMAL:
return kNormalPriority;
default:
RTC_NOTREACHED();
break;
}
return kNormalPriority;
}
int64_t GetTick() {
static const UINT kPeriod = 1;
bool high_res = (timeBeginPeriod(kPeriod) == TIMERR_NOERROR);
int64_t ret = TimeMillis();
if (high_res)
timeEndPeriod(kPeriod);
return ret;
}
class DelayedTaskInfo {
public:
// Default ctor needed to support priority_queue::pop().
DelayedTaskInfo() {}
DelayedTaskInfo(uint32_t milliseconds, std::unique_ptr<QueuedTask> task)
: due_time_(GetTick() + milliseconds), task_(std::move(task)) {}
DelayedTaskInfo(DelayedTaskInfo&&) = default;
// Implement for priority_queue.
bool operator>(const DelayedTaskInfo& other) const {
return due_time_ > other.due_time_;
}
// Required by priority_queue::pop().
DelayedTaskInfo& operator=(DelayedTaskInfo&& other) = default;
// See below for why this method is const.
void Run() const {
RTC_DCHECK(due_time_);
task_->Run() ? task_.reset() : static_cast<void>(task_.release());
}
int64_t due_time() const { return due_time_; }
private:
int64_t due_time_ = 0; // Absolute timestamp in milliseconds.
// |task| needs to be mutable because std::priority_queue::top() returns
// a const reference and a key in an ordered queue must not be changed.
// There are two basic workarounds, one using const_cast, which would also
// make the key (|due_time|), non-const and the other is to make the non-key
// (|task|), mutable.
// Because of this, the |task| variable is made private and can only be
// mutated by calling the |Run()| method.
mutable std::unique_ptr<QueuedTask> task_;
};
class MultimediaTimer {
public:
// Note: We create an event that requires manual reset.
MultimediaTimer() : event_(::CreateEvent(nullptr, true, false, nullptr)) {}
~MultimediaTimer() {
Cancel();
::CloseHandle(event_);
}
bool StartOneShotTimer(UINT delay_ms) {
RTC_DCHECK_EQ(0, timer_id_);
RTC_DCHECK(event_ != nullptr);
timer_id_ =
::timeSetEvent(delay_ms, 0, reinterpret_cast<LPTIMECALLBACK>(event_), 0,
TIME_ONESHOT | TIME_CALLBACK_EVENT_SET);
return timer_id_ != 0;
}
void Cancel() {
::ResetEvent(event_);
if (timer_id_) {
::timeKillEvent(timer_id_);
timer_id_ = 0;
}
}
HANDLE* event_for_wait() { return &event_; }
private:
HANDLE event_ = nullptr;
MMRESULT timer_id_ = 0;
RTC_DISALLOW_COPY_AND_ASSIGN(MultimediaTimer);
};
} // namespace
class TaskQueue::ThreadState {
public:
explicit ThreadState(HANDLE in_queue) : in_queue_(in_queue) {}
~ThreadState() {}
void RunThreadMain();
private:
bool ProcessQueuedMessages();
void RunDueTasks();
void ScheduleNextTimer();
void CancelTimers();
// Since priority_queue<> by defult orders items in terms of
// largest->smallest, using std::less<>, and we want smallest->largest,
// we would like to use std::greater<> here. Alas it's only available in
// C++14 and later, so we roll our own compare template that that relies on
// operator<().
template <typename T>
struct greater {
bool operator()(const T& l, const T& r) { return l > r; }
};
MultimediaTimer timer_;
std::priority_queue<DelayedTaskInfo,
std::vector<DelayedTaskInfo>,
greater<DelayedTaskInfo>>
timer_tasks_;
UINT_PTR timer_id_ = 0;
HANDLE in_queue_;
};
TaskQueue::TaskQueue(const char* queue_name, Priority priority /*= NORMAL*/)
: thread_(&TaskQueue::ThreadMain,
this,
queue_name,
TaskQueuePriorityToThreadPriority(priority)),
in_queue_(::CreateEvent(nullptr, true, false, nullptr)) {
RTC_DCHECK(queue_name);
RTC_DCHECK(in_queue_);
thread_.Start();
Event event(false, false);
ThreadStartupData startup = {&event, this};
RTC_CHECK(thread_.QueueAPC(&InitializeQueueThread,
reinterpret_cast<ULONG_PTR>(&startup)));
event.Wait(Event::kForever);
}
TaskQueue::~TaskQueue() {
RTC_DCHECK(!IsCurrent());
while (!::PostThreadMessage(thread_.GetThreadRef(), WM_QUIT, 0, 0)) {
RTC_CHECK_EQ(ERROR_NOT_ENOUGH_QUOTA, ::GetLastError());
Sleep(1);
}
thread_.Stop();
::CloseHandle(in_queue_);
}
// static
TaskQueue* TaskQueue::Current() {
return static_cast<TaskQueue*>(::TlsGetValue(GetQueuePtrTls()));
}
bool TaskQueue::IsCurrent() const {
return IsThreadRefEqual(thread_.GetThreadRef(), CurrentThreadRef());
}
void TaskQueue::PostTask(std::unique_ptr<QueuedTask> task) {
rtc::CritScope lock(&pending_lock_);
pending_.push(std::move(task));
::SetEvent(in_queue_);
}
void TaskQueue::PostDelayedTask(std::unique_ptr<QueuedTask> task,
uint32_t milliseconds) {
if (!milliseconds) {
PostTask(std::move(task));
return;
}
// TODO(tommi): Avoid this allocation. It is currently here since
// the timestamp stored in the task info object, is a 64bit timestamp
// and WPARAM is 32bits in 32bit builds. Otherwise, we could pass the
// task pointer and timestamp as LPARAM and WPARAM.
auto* task_info = new DelayedTaskInfo(milliseconds, std::move(task));
if (!::PostThreadMessage(thread_.GetThreadRef(), WM_QUEUE_DELAYED_TASK, 0,
reinterpret_cast<LPARAM>(task_info))) {
delete task_info;
}
}
void TaskQueue::PostTaskAndReply(std::unique_ptr<QueuedTask> task,
std::unique_ptr<QueuedTask> reply,
TaskQueue* reply_queue) {
QueuedTask* task_ptr = task.release();
QueuedTask* reply_task_ptr = reply.release();
DWORD reply_thread_id = reply_queue->thread_.GetThreadRef();
PostTask([task_ptr, reply_task_ptr, reply_thread_id]() {
if (task_ptr->Run())
delete task_ptr;
// If the thread's message queue is full, we can't queue the task and will
// have to drop it (i.e. delete).
if (!::PostThreadMessage(reply_thread_id, WM_RUN_TASK, 0,
reinterpret_cast<LPARAM>(reply_task_ptr))) {
delete reply_task_ptr;
}
});
}
void TaskQueue::PostTaskAndReply(std::unique_ptr<QueuedTask> task,
std::unique_ptr<QueuedTask> reply) {
return PostTaskAndReply(std::move(task), std::move(reply), Current());
}
void TaskQueue::RunPendingTasks() {
while (true) {
std::unique_ptr<QueuedTask> task;
{
rtc::CritScope lock(&pending_lock_);
if (pending_.empty())
break;
task = std::move(pending_.front());
pending_.pop();
}
if (!task->Run())
task.release();
}
}
// static
void TaskQueue::ThreadMain(void* context) {
ThreadState state(static_cast<TaskQueue*>(context)->in_queue_);
state.RunThreadMain();
}
void TaskQueue::ThreadState::RunThreadMain() {
HANDLE handles[2] = { *timer_.event_for_wait(), in_queue_ };
while (true) {
// Make sure we do an alertable wait as that's required to allow APCs to run
// (e.g. required for InitializeQueueThread and stopping the thread in
// PlatformThread).
DWORD result = ::MsgWaitForMultipleObjectsEx(
arraysize(handles), handles, INFINITE, QS_ALLEVENTS, MWMO_ALERTABLE);
RTC_CHECK_NE(WAIT_FAILED, result);
if (result == (WAIT_OBJECT_0 + 2)) {
// There are messages in the message queue that need to be handled.
if (!ProcessQueuedMessages())
break;
}
if (result == WAIT_OBJECT_0 || (!timer_tasks_.empty() &&
::WaitForSingleObject(*timer_.event_for_wait(), 0) == WAIT_OBJECT_0)) {
// The multimedia timer was signaled.
timer_.Cancel();
RunDueTasks();
ScheduleNextTimer();
}
if (result == (WAIT_OBJECT_0 + 1)) {
::ResetEvent(in_queue_);
TaskQueue::Current()->RunPendingTasks();
}
}
}
bool TaskQueue::ThreadState::ProcessQueuedMessages() {
MSG msg = {};
// To protect against overly busy message queues, we limit the time
// we process tasks to a few milliseconds. If we don't do that, there's
// a chance that timer tasks won't ever run.
static const int kMaxTaskProcessingTimeMs = 500;
auto start = GetTick();
while (::PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE) &&
msg.message != WM_QUIT) {
if (!msg.hwnd) {
switch (msg.message) {
// TODO(tommi): Stop using this way of queueing tasks.
case WM_RUN_TASK: {
QueuedTask* task = reinterpret_cast<QueuedTask*>(msg.lParam);
if (task->Run())
delete task;
break;
}
case WM_QUEUE_DELAYED_TASK: {
std::unique_ptr<DelayedTaskInfo> info(
reinterpret_cast<DelayedTaskInfo*>(msg.lParam));
bool need_to_schedule_timers =
timer_tasks_.empty() ||
timer_tasks_.top().due_time() > info->due_time();
timer_tasks_.emplace(std::move(*info.get()));
if (need_to_schedule_timers) {
CancelTimers();
ScheduleNextTimer();
}
break;
}
case WM_TIMER: {
RTC_DCHECK_EQ(timer_id_, msg.wParam);
::KillTimer(nullptr, msg.wParam);
timer_id_ = 0;
RunDueTasks();
ScheduleNextTimer();
break;
}
default:
RTC_NOTREACHED();
break;
}
} else {
::TranslateMessage(&msg);
::DispatchMessage(&msg);
}
if (GetTick() > start + kMaxTaskProcessingTimeMs)
break;
}
return msg.message != WM_QUIT;
}
void TaskQueue::ThreadState::RunDueTasks() {
RTC_DCHECK(!timer_tasks_.empty());
auto now = GetTick();
do {
const auto& top = timer_tasks_.top();
if (top.due_time() > now)
break;
top.Run();
timer_tasks_.pop();
} while (!timer_tasks_.empty());
}
void TaskQueue::ThreadState::ScheduleNextTimer() {
RTC_DCHECK_EQ(timer_id_, 0);
if (timer_tasks_.empty())
return;
const auto& next_task = timer_tasks_.top();
int64_t delay_ms = std::max(0ll, next_task.due_time() - GetTick());
uint32_t milliseconds = rtc::dchecked_cast<uint32_t>(delay_ms);
if (!timer_.StartOneShotTimer(milliseconds))
timer_id_ = ::SetTimer(nullptr, 0, milliseconds, nullptr);
}
void TaskQueue::ThreadState::CancelTimers() {
timer_.Cancel();
if (timer_id_) {
::KillTimer(nullptr, timer_id_);
timer_id_ = 0;
}
}
} // namespace rtc