From 44e0efe0e67797702c0a71e3798d2d2c047f1368 Mon Sep 17 00:00:00 2001
From: kthelgason <kthelgason@webrtc.org>
Date: Wed, 2 Nov 2016 10:28:20 -0700
Subject: [PATCH] Use queue label as id in SequencedTaskChecker when not
 running on TaskQueue

This is intended to make SequencedTaskChecker work for native dispatch queues
on iOS and macOS. These labels can be compared by their pointers to determine
if a task is running on the same queue.

BUG=webrtc:6643

Review-Url: https://codereview.webrtc.org/2464383002
Cr-Commit-Position: refs/heads/master@{#14900}
---
 webrtc/base/sequenced_task_checker_impl.cc | 12 +++++++++++-
 webrtc/base/sequenced_task_checker_impl.h  |  3 ++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/webrtc/base/sequenced_task_checker_impl.cc b/webrtc/base/sequenced_task_checker_impl.cc
index 615f44c2b5..f03e0b6796 100644
--- a/webrtc/base/sequenced_task_checker_impl.cc
+++ b/webrtc/base/sequenced_task_checker_impl.cc
@@ -10,6 +10,10 @@
 
 #include "webrtc/base/sequenced_task_checker_impl.h"
 
+#if defined(WEBRTC_MAC)
+#include <dispatch/dispatch.h>
+#endif
+
 #include "webrtc/base/platform_thread.h"
 #include "webrtc/base/sequenced_task_checker.h"
 #include "webrtc/base/task_queue.h"
@@ -22,7 +26,13 @@ SequencedTaskCheckerImpl::SequencedTaskCheckerImpl()
 SequencedTaskCheckerImpl::~SequencedTaskCheckerImpl() {}
 
 bool SequencedTaskCheckerImpl::CalledSequentially() const {
-  TaskQueue* current_queue = TaskQueue::Current();
+  QueueId current_queue = TaskQueue::Current();
+#if defined(WEBRTC_MAC)
+  // If we're not running on a TaskQueue, use the system dispatch queue
+  // label as an identifier.
+  if (current_queue == nullptr)
+    current_queue = dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL);
+#endif
   CritScope scoped_lock(&lock_);
   if (!attached_) {  // true if previously detached.
     valid_queue_ = current_queue;
diff --git a/webrtc/base/sequenced_task_checker_impl.h b/webrtc/base/sequenced_task_checker_impl.h
index 96cb32de6d..684b1dc502 100644
--- a/webrtc/base/sequenced_task_checker_impl.h
+++ b/webrtc/base/sequenced_task_checker_impl.h
@@ -34,10 +34,11 @@ class SequencedTaskCheckerImpl {
   void Detach();
 
  private:
+  typedef const void* QueueId;
   CriticalSection lock_;
   ThreadChecker thread_checker_;
   mutable bool attached_;
-  mutable TaskQueue* valid_queue_;
+  mutable QueueId valid_queue_;
 };
 
 }  // namespace rtc