From 00e71ef49e9138c3253a3f22ff0c717033bbb986 Mon Sep 17 00:00:00 2001
From: Danil Chapovalov <danilchap@webrtc.org>
Date: Tue, 11 Jun 2019 18:01:56 +0200
Subject: [PATCH] Fix TaskQueueLibevent::PostTask when used on the same
 TaskQueue

Stop using event_base_once because it doesn't guarantee to free QueuedTask when task not run and thus may break TaskQueue guarantee all posted tasks are eventually deleted

Bug: webrtc:10731, webrtc:10278
Change-Id: Id073a6092cf603cac5768da7a0770371053b20cc
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/141420
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28241}
---
 rtc_base/task_queue_libevent.cc | 44 +++++++++------------------------
 1 file changed, 12 insertions(+), 32 deletions(-)

diff --git a/rtc_base/task_queue_libevent.cc b/rtc_base/task_queue_libevent.cc
index 38704c89ae..9a01f464c1 100644
--- a/rtc_base/task_queue_libevent.cc
+++ b/rtc_base/task_queue_libevent.cc
@@ -121,7 +121,6 @@ class TaskQueueLibevent final : public TaskQueueBase {
 
   static void ThreadMain(void* context);
   static void OnWakeup(int socket, short flags, void* context);  // NOLINT
-  static void RunTask(int fd, short flags, void* context);       // NOLINT
   static void RunTimer(int fd, short flags, void* context);      // NOLINT
 
   bool is_active_ = true;
@@ -214,30 +213,18 @@ void TaskQueueLibevent::Delete() {
 }
 
 void TaskQueueLibevent::PostTask(std::unique_ptr<QueuedTask> task) {
-  RTC_DCHECK(task.get());
-  // libevent isn't thread safe.  This means that we can't use methods such
-  // as event_base_once to post tasks to the worker thread from a different
-  // thread.  However, we can use it when posting from the worker thread itself.
-  if (IsCurrent()) {
-    if (event_base_once(event_base_, -1, EV_TIMEOUT,
-                        &TaskQueueLibevent::RunTask, task.get(),
-                        nullptr) == 0) {
-      task.release();
-    }
-  } else {
-    QueuedTask* task_id = task.get();  // Only used for comparison.
-    {
-      rtc::CritScope lock(&pending_lock_);
-      pending_.push_back(std::move(task));
-    }
-    char message = kRunTask;
-    if (write(wakeup_pipe_in_, &message, sizeof(message)) != sizeof(message)) {
-      RTC_LOG(WARNING) << "Failed to queue task.";
-      rtc::CritScope lock(&pending_lock_);
-      pending_.remove_if([task_id](std::unique_ptr<QueuedTask>& t) {
-        return t.get() == task_id;
-      });
-    }
+  QueuedTask* task_id = task.get();  // Only used for comparison.
+  {
+    rtc::CritScope lock(&pending_lock_);
+    pending_.push_back(std::move(task));
+  }
+  char message = kRunTask;
+  if (write(wakeup_pipe_in_, &message, sizeof(message)) != sizeof(message)) {
+    RTC_LOG(WARNING) << "Failed to queue task.";
+    rtc::CritScope lock(&pending_lock_);
+    pending_.remove_if([task_id](std::unique_ptr<QueuedTask>& t) {
+      return t.get() == task_id;
+    });
   }
 }
 
@@ -302,13 +289,6 @@ void TaskQueueLibevent::OnWakeup(int socket,
   }
 }
 
-// static
-void TaskQueueLibevent::RunTask(int fd, short flags, void* context) {  // NOLINT
-  auto* task = static_cast<QueuedTask*>(context);
-  if (task->Run())
-    delete task;
-}
-
 // static
 void TaskQueueLibevent::RunTimer(int fd,
                                  short flags,  // NOLINT