commit 7866cfe575e85978dba50b1c4a1877a325601fe1
author nisse <nisse@webrtc.org> Wed Apr 26 01:45:31 2017 -0700
committer Commit bot <commit-bot@chromium.org> Wed Apr 26 08:45:31 2017 +0000
tree d2d1de6f4e6d266eba2d91563f24dbb401ca0777
parent 20a60853a67193b7fe2ae284ae606958dbf22206

Move autowrap from ThreadManager constructor to Thread::Current.

This is in preparation for a WrapCurrentThread method,
or AutoThread constructor, taking a socket
server as argument, to eliminate the need for the
MessageQueue::set_socketserver method and its lock.

No intended change in behaviour; the ThreadManager constructor
records the calling thread id, and autowrap is still restricted to
that thread. Behavior when NO_MAIN_THREAD_WRAPPING is defined is
also unchanged.

Also makes the ThreadManager a singleton, with private constructor
and destructor. And marks its destructor as RTC_NOTREACHED, since
by the documentation for RTC_DEFINE_STATIC_LOCAL, the intention is to
leak the object and never destruct it.

BUG=webrtc:7501

Review-Url: https://codereview.webrtc.org/2833993003
Cr-Commit-Position: refs/heads/master@{#17879}

webrtc/base/thread.cc

diff --git a/webrtc/base/thread.cc b/webrtc/base/thread.cc
index b5be475..9a71c1a 100644
--- a/webrtc/base/thread.cc
+++ b/webrtc/base/thread.cc
@@ -31,23 +31,32 @@
   return &thread_manager;
 }
 
+ThreadManager::~ThreadManager() {
+  // By above RTC_DEFINE_STATIC_LOCAL.
+  RTC_NOTREACHED() << "ThreadManager should never be destructed.";
+}
+
 // static
 Thread* Thread::Current() {
-  return ThreadManager::Instance()->CurrentThread();
+  ThreadManager* manager = ThreadManager::Instance();
+  Thread* thread = manager->CurrentThread();
+
+#ifndef NO_MAIN_THREAD_WRAPPING
+  // Only autowrap the thread which instantiated the ThreadManager.
+  if (!thread && manager->IsMainThread()) {
+    thread = new Thread();
+    thread->WrapCurrentWithThreadManager(manager, true);
+  }
+#endif
+
+  return thread;
 }
 
 #if defined(WEBRTC_POSIX)
 #if !defined(WEBRTC_MAC)
 ThreadManager::ThreadManager() {
+  main_thread_ref_ = CurrentThreadRef();
   pthread_key_create(&key_, nullptr);
-#ifndef NO_MAIN_THREAD_WRAPPING
-  WrapCurrentThread();
-#endif
-}
-
-ThreadManager::~ThreadManager() {
-  UnwrapCurrentThread();
-  pthread_key_delete(key_);
 }
 #endif
 
@@ -62,15 +71,8 @@
 
 #if defined(WEBRTC_WIN)
 ThreadManager::ThreadManager() {
+  main_thread_ref_ = CurrentThreadRef();
   key_ = TlsAlloc();
-#ifndef NO_MAIN_THREAD_WRAPPING
-  WrapCurrentThread();
-#endif
-}
-
-ThreadManager::~ThreadManager() {
-  UnwrapCurrentThread();
-  TlsFree(key_);
 }
 
 Thread *ThreadManager::CurrentThread() {
@@ -99,6 +101,10 @@
   }
 }
 
+bool ThreadManager::IsMainThread() {
+  return IsThreadRefEqual(CurrentThreadRef(), main_thread_ref_);
+}
+
 Thread::ScopedDisallowBlockingCalls::ScopedDisallowBlockingCalls()
   : thread_(Thread::Current()),
     previous_state_(thread_->SetAllowBlockingCalls(false)) {
@@ -142,6 +148,10 @@
   DoDestroy();
 }
 
+bool Thread::IsCurrent() const {
+  return ThreadManager::Instance()->CurrentThread() == this;
+}
+
 std::unique_ptr<Thread> Thread::CreateWithSocketServer() {
   return std::unique_ptr<Thread>(new Thread(SocketServer::CreateDefault()));
 }