commit c89fdd716c4c8af608017c76f75bf27e4c3d602e
author Markus Handell <handellm@webrtc.org> Wed May 05 10:42:04 2021 +0200
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed May 05 09:59:07 2021 +0000
tree 0631f7fcb63b0a408773d4737711c75709cd1ce9
parent 1c5c2178fed4068a94c4d3a71a7da428cac22151

Refactor the PlatformThread API.

PlatformThread's API is using old style function pointers, causes
casting, is unintuitive and forces artificial call sequences, and
is additionally possible to misuse in release mode.

Fix this by an API face lift:
1. The class is turned into a handle, which can be empty.
2. The only way of getting a non-empty PlatformThread is by calling
SpawnJoinable or SpawnDetached, clearly conveying the semantics to the
code reader.
3. Handles can be Finalized, which works differently for joinable and
detached threads:
  a) Handles for detached threads are simply closed where applicable.
  b) Joinable threads are joined before handles are closed.
4. The destructor finalizes handles. No explicit call is needed.

Fixed: webrtc:12727
Change-Id: Id00a0464edf4fc9e552b6a1fbb5d2e1280e88811
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215075
Commit-Queue: Markus Handell <handellm@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33923}

rtc_base/task_queue_libevent.cc

diff --git a/rtc_base/task_queue_libevent.cc b/rtc_base/task_queue_libevent.cc
index 71a9e8a..9096986 100644
--- a/rtc_base/task_queue_libevent.cc
+++ b/rtc_base/task_queue_libevent.cc
@@ -93,16 +93,12 @@
 rtc::ThreadPriority TaskQueuePriorityToThreadPriority(Priority priority) {
   switch (priority) {
     case Priority::HIGH:
-      return rtc::kRealtimePriority;
+      return rtc::ThreadPriority::kRealtime;
     case Priority::LOW:
-      return rtc::kLowPriority;
+      return rtc::ThreadPriority::kLow;
     case Priority::NORMAL:
-      return rtc::kNormalPriority;
-    default:
-      RTC_NOTREACHED();
-      break;
+      return rtc::ThreadPriority::kNormal;
   }
-  return rtc::kNormalPriority;
 }
 
 class TaskQueueLibevent final : public TaskQueueBase {
@@ -120,7 +116,6 @@
 
   ~TaskQueueLibevent() override = default;
 
-  static void ThreadMain(void* context);
   static void OnWakeup(int socket, short flags, void* context);  // NOLINT
   static void RunTimer(int fd, short flags, void* context);      // NOLINT
 
@@ -172,11 +167,7 @@
 
 TaskQueueLibevent::TaskQueueLibevent(absl::string_view queue_name,
                                      rtc::ThreadPriority priority)
-    : event_base_(event_base_new()),
-      thread_(&TaskQueueLibevent::ThreadMain,
-              this,
-              queue_name,
-              rtc::ThreadAttributes().SetPriority(priority)) {
+    : event_base_(event_base_new()) {
   int fds[2];
   RTC_CHECK(pipe(fds) == 0);
   SetNonBlocking(fds[0]);
@@ -187,7 +178,18 @@
   EventAssign(&wakeup_event_, event_base_, wakeup_pipe_out_,
               EV_READ | EV_PERSIST, OnWakeup, this);
   event_add(&wakeup_event_, 0);
-  thread_.Start();
+  thread_ = rtc::PlatformThread::SpawnJoinable(
+      [this] {
+        {
+          CurrentTaskQueueSetter set_current(this);
+          while (is_active_)
+            event_base_loop(event_base_, 0);
+        }
+
+        for (TimerEvent* timer : pending_timers_)
+          delete timer;
+      },
+      queue_name, rtc::ThreadAttributes().SetPriority(priority));
 }
 
 void TaskQueueLibevent::Delete() {
@@ -202,7 +204,7 @@
     nanosleep(&ts, nullptr);
   }
 
-  thread_.Stop();
+  thread_.Finalize();
 
   event_del(&wakeup_event_);
 
@@ -256,20 +258,6 @@
 }
 
 // static
-void TaskQueueLibevent::ThreadMain(void* context) {
-  TaskQueueLibevent* me = static_cast<TaskQueueLibevent*>(context);
-
-  {
-    CurrentTaskQueueSetter set_current(me);
-    while (me->is_active_)
-      event_base_loop(me->event_base_, 0);
-  }
-
-  for (TimerEvent* timer : me->pending_timers_)
-    delete timer;
-}
-
-// static
 void TaskQueueLibevent::OnWakeup(int socket,
                                  short flags,  // NOLINT
                                  void* context) {