Repo created

TMessagesProj/jni/voip/webrtc/rtc_base/task_queue_stdlib.cc

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+/*
+ *  Copyright 2018 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 "rtc_base/task_queue_stdlib.h"
+
+#include <string.h>
+
+#include <algorithm>
+#include <map>
+#include <memory>
+#include <queue>
+#include <utility>
+
+#include "absl/functional/any_invocable.h"
+#include "absl/strings/string_view.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/time_delta.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/event.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/numerics/divide_round.h"
+#include "rtc_base/platform_thread.h"
+#include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/thread_annotations.h"
+#include "rtc_base/time_utils.h"
+
+namespace webrtc {
+namespace {
+
+rtc::ThreadPriority TaskQueuePriorityToThreadPriority(
+    TaskQueueFactory::Priority priority) {
+  switch (priority) {
+    case TaskQueueFactory::Priority::HIGH:
+      return rtc::ThreadPriority::kRealtime;
+    case TaskQueueFactory::Priority::LOW:
+      return rtc::ThreadPriority::kLow;
+    case TaskQueueFactory::Priority::NORMAL:
+      return rtc::ThreadPriority::kNormal;
+  }
+}
+
+class TaskQueueStdlib final : public TaskQueueBase {
+ public:
+  TaskQueueStdlib(absl::string_view queue_name, rtc::ThreadPriority priority);
+  ~TaskQueueStdlib() override = default;
+
+  void Delete() override;
+
+ protected:
+  void PostTaskImpl(absl::AnyInvocable<void() &&> task,
+                    const PostTaskTraits& traits,
+                    const Location& location) override;
+  void PostDelayedTaskImpl(absl::AnyInvocable<void() &&> task,
+                           TimeDelta delay,
+                           const PostDelayedTaskTraits& traits,
+                           const Location& location) override;
+
+ private:
+  using OrderId = uint64_t;
+
+  struct DelayedEntryTimeout {
+    // TODO(bugs.webrtc.org/13756): Migrate to Timestamp.
+    int64_t next_fire_at_us{};
+    OrderId order{};
+
+    bool operator<(const DelayedEntryTimeout& o) const {
+      return std::tie(next_fire_at_us, order) <
+             std::tie(o.next_fire_at_us, o.order);
+    }
+  };
+
+  struct NextTask {
+    bool final_task = false;
+    absl::AnyInvocable<void() &&> run_task;
+    TimeDelta sleep_time = rtc::Event::kForever;
+  };
+
+  static rtc::PlatformThread InitializeThread(TaskQueueStdlib* me,
+                                              absl::string_view queue_name,
+                                              rtc::ThreadPriority priority);
+
+  NextTask GetNextTask();
+
+  void ProcessTasks();
+
+  void NotifyWake();
+
+  // Signaled whenever a new task is pending.
+  rtc::Event flag_notify_;
+
+  Mutex pending_lock_;
+
+  // Indicates if the worker thread needs to shutdown now.
+  bool thread_should_quit_ RTC_GUARDED_BY(pending_lock_) = false;
+
+  // Holds the next order to use for the next task to be
+  // put into one of the pending queues.
+  OrderId thread_posting_order_ RTC_GUARDED_BY(pending_lock_) = 0;
+
+  // The list of all pending tasks that need to be processed in the
+  // FIFO queue ordering on the worker thread.
+  std::queue<std::pair<OrderId, absl::AnyInvocable<void() &&>>> pending_queue_
+      RTC_GUARDED_BY(pending_lock_);
+
+  // The list of all pending tasks that need to be processed at a future
+  // time based upon a delay. On the off change the delayed task should
+  // happen at exactly the same time interval as another task then the
+  // task is processed based on FIFO ordering. std::priority_queue was
+  // considered but rejected due to its inability to extract the
+  // move-only value out of the queue without the presence of a hack.
+  std::map<DelayedEntryTimeout, absl::AnyInvocable<void() &&>> delayed_queue_
+      RTC_GUARDED_BY(pending_lock_);
+
+  // Contains the active worker thread assigned to processing
+  // tasks (including delayed tasks).
+  // Placing this last ensures the thread doesn't touch uninitialized attributes
+  // throughout it's lifetime.
+  rtc::PlatformThread thread_;
+};
+
+TaskQueueStdlib::TaskQueueStdlib(absl::string_view queue_name,
+                                 rtc::ThreadPriority priority)
+    : flag_notify_(/*manual_reset=*/false, /*initially_signaled=*/false),
+      thread_(InitializeThread(this, queue_name, priority)) {}
+
+// static
+rtc::PlatformThread TaskQueueStdlib::InitializeThread(
+    TaskQueueStdlib* me,
+    absl::string_view queue_name,
+    rtc::ThreadPriority priority) {
+  rtc::Event started;
+  auto thread = rtc::PlatformThread::SpawnJoinable(
+      [&started, me] {
+        CurrentTaskQueueSetter set_current(me);
+        started.Set();
+        me->ProcessTasks();
+      },
+      queue_name, rtc::ThreadAttributes().SetPriority(priority));
+  started.Wait(rtc::Event::kForever);
+  return thread;
+}
+
+void TaskQueueStdlib::Delete() {
+  RTC_DCHECK(!IsCurrent());
+
+  {
+    MutexLock lock(&pending_lock_);
+    thread_should_quit_ = true;
+  }
+
+  NotifyWake();
+
+  delete this;
+}
+
+void TaskQueueStdlib::PostTaskImpl(absl::AnyInvocable<void() &&> task,
+                                   const PostTaskTraits& traits,
+                                   const Location& location) {
+  {
+    MutexLock lock(&pending_lock_);
+    pending_queue_.push(
+        std::make_pair(++thread_posting_order_, std::move(task)));
+  }
+
+  NotifyWake();
+}
+
+void TaskQueueStdlib::PostDelayedTaskImpl(absl::AnyInvocable<void() &&> task,
+                                          TimeDelta delay,
+                                          const PostDelayedTaskTraits& traits,
+                                          const Location& location) {
+  DelayedEntryTimeout delayed_entry;
+  delayed_entry.next_fire_at_us = rtc::TimeMicros() + delay.us();
+
+  {
+    MutexLock lock(&pending_lock_);
+    delayed_entry.order = ++thread_posting_order_;
+    delayed_queue_[delayed_entry] = std::move(task);
+  }
+
+  NotifyWake();
+}
+
+TaskQueueStdlib::NextTask TaskQueueStdlib::GetNextTask() {
+  NextTask result;
+
+  const int64_t tick_us = rtc::TimeMicros();
+
+  MutexLock lock(&pending_lock_);
+
+  if (thread_should_quit_) {
+    result.final_task = true;
+    return result;
+  }
+
+  if (delayed_queue_.size() > 0) {
+    auto delayed_entry = delayed_queue_.begin();
+    const auto& delay_info = delayed_entry->first;
+    auto& delay_run = delayed_entry->second;
+    if (tick_us >= delay_info.next_fire_at_us) {
+      if (pending_queue_.size() > 0) {
+        auto& entry = pending_queue_.front();
+        auto& entry_order = entry.first;
+        auto& entry_run = entry.second;
+        if (entry_order < delay_info.order) {
+          result.run_task = std::move(entry_run);
+          pending_queue_.pop();
+          return result;
+        }
+      }
+
+      result.run_task = std::move(delay_run);
+      delayed_queue_.erase(delayed_entry);
+      return result;
+    }
+
+    result.sleep_time = TimeDelta::Millis(
+        DivideRoundUp(delay_info.next_fire_at_us - tick_us, 1'000));
+  }
+
+  if (pending_queue_.size() > 0) {
+    auto& entry = pending_queue_.front();
+    result.run_task = std::move(entry.second);
+    pending_queue_.pop();
+  }
+
+  return result;
+}
+
+void TaskQueueStdlib::ProcessTasks() {
+  while (true) {
+    auto task = GetNextTask();
+
+    if (task.final_task)
+      break;
+
+    if (task.run_task) {
+      // process entry immediately then try again
+      std::move(task.run_task)();
+
+      // Attempt to run more tasks before going to sleep.
+      continue;
+    }
+
+    flag_notify_.Wait(task.sleep_time);
+  }
+
+  // Ensure remaining deleted tasks are destroyed with Current() set up to this
+  // task queue.
+  std::queue<std::pair<OrderId, absl::AnyInvocable<void() &&>>> pending_queue;
+  {
+    MutexLock lock(&pending_lock_);
+    pending_queue_.swap(pending_queue);
+  }
+  pending_queue = {};
+#if RTC_DCHECK_IS_ON
+  MutexLock lock(&pending_lock_);
+  RTC_DCHECK(pending_queue_.empty());
+#endif
+}
+
+void TaskQueueStdlib::NotifyWake() {
+  // The queue holds pending tasks to complete. Either tasks are to be
+  // executed immediately or tasks are to be run at some future delayed time.
+  // For immediate tasks the task queue's thread is busy running the task and
+  // the thread will not be waiting on the flag_notify_ event. If no immediate
+  // tasks are available but a delayed task is pending then the thread will be
+  // waiting on flag_notify_ with a delayed time-out of the nearest timed task
+  // to run. If no immediate or pending tasks are available, the thread will
+  // wait on flag_notify_ until signaled that a task has been added (or the
+  // thread to be told to shutdown).
+
+  // In all cases, when a new immediate task, delayed task, or request to
+  // shutdown the thread is added the flag_notify_ is signaled after. If the
+  // thread was waiting then the thread will wake up immediately and re-assess
+  // what task needs to be run next (i.e. run a task now, wait for the nearest
+  // timed delayed task, or shutdown the thread). If the thread was not waiting
+  // then the thread will remained signaled to wake up the next time any
+  // attempt to wait on the flag_notify_ event occurs.
+
+  // Any immediate or delayed pending task (or request to shutdown the thread)
+  // must always be added to the queue prior to signaling flag_notify_ to wake
+  // up the possibly sleeping thread. This prevents a race condition where the
+  // thread is notified to wake up but the task queue's thread finds nothing to
+  // do so it waits once again to be signaled where such a signal may never
+  // happen.
+  flag_notify_.Set();
+}
+
+class TaskQueueStdlibFactory final : public TaskQueueFactory {
+ public:
+  std::unique_ptr<TaskQueueBase, TaskQueueDeleter> CreateTaskQueue(
+      absl::string_view name,
+      Priority priority) const override {
+    return std::unique_ptr<TaskQueueBase, TaskQueueDeleter>(
+        new TaskQueueStdlib(name, TaskQueuePriorityToThreadPriority(priority)));
+  }
+};
+
+}  // namespace
+
+std::unique_ptr<TaskQueueFactory> CreateTaskQueueStdlibFactory() {
+  return std::make_unique<TaskQueueStdlibFactory>();
+}
+
+}  // namespace webrtc