Do not block in SimpleThread::Start().

base/threading/simple_thread.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/threading/simple_thread.h"
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_restrictions.h"
 
 namespace base {
 
 SimpleThread::SimpleThread(const std::string& name_prefix)
     : SimpleThread(name_prefix, Options()) {}
 
 SimpleThread::SimpleThread(const std::string& name_prefix,
                            const Options& options)
     : name_prefix_(name_prefix),
       options_(options),
-      event_(WaitableEvent::ResetPolicy::MANUAL,
-             WaitableEvent::InitialState::NOT_SIGNALED) {}
+      id_event_(WaitableEvent::ResetPolicy::MANUAL,
+                WaitableEvent::InitialState::NOT_SIGNALED) {}
 
 SimpleThread::~SimpleThread() {
-  DCHECK(HasBeenStarted()) << "SimpleThread was never started.";
-  DCHECK(!options_.joinable || HasBeenJoined())
+#if DCHECK_IS_ON()
+  DCHECK(has_been_started_) << "SimpleThread was never started.";
+  DCHECK(!options_.joinable || has_been_joined_)
       << "Joinable SimpleThread destroyed without being Join()ed.";
+#endif
 }
 
 void SimpleThread::Start() {
-  DCHECK(!HasBeenStarted()) << "Tried to Start a thread multiple times.";
+#if DCHECK_IS_ON()
+  DCHECK(!has_been_started_) << "Tried to Start a thread multiple times.";
+
+  // Set |has_been_started_| before creating the thread so that Run() sees it.
+  // Otherwise, Run() could hit a DCHECK when deleting |this|.

[gab, 2017/02/06 21:19:28]

// Set |has_been_started_| before creating the thread as no member access is
allowed after.

(more than this is redundant with comment at bottom)

[fdoray, 2017/02/07 12:57:16]

Done.

+  has_been_started_ = true;
+#endif
   bool success =
       options_.joinable
           ? PlatformThread::CreateWithPriority(options_.stack_size, this,
                                                &thread_, options_.priority)
           : PlatformThread::CreateNonJoinableWithPriority(
                 options_.stack_size, this, options_.priority);
   DCHECK(success);
-  ThreadRestrictions::ScopedAllowWait allow_wait;
-  event_.Wait();  // Wait for the thread to complete initialization.
+
+  // No member access after creating the thread, |this| can be deleted at any
+  // point after invoking Run() on non-joinable threads.
 }
 
 void SimpleThread::Join() {
+#if DCHECK_IS_ON()
   DCHECK(options_.joinable) << "A non-joinable thread can't be joined.";
-  DCHECK(HasBeenStarted()) << "Tried to Join a never-started thread.";
-  DCHECK(!HasBeenJoined()) << "Tried to Join a thread multiple times.";
+  DCHECK(has_been_started_) << "Tried to Join a never-started thread.";
+  DCHECK(!has_been_joined_) << "Tried to Join a thread multiple times.";
+#endif
   PlatformThread::Join(thread_);
   thread_ = PlatformThreadHandle();
-  joined_ = true;
+#if DCHECK_IS_ON()
+  has_been_joined_ = true;
+#endif
 }
 
-bool SimpleThread::HasBeenStarted() {
-  ThreadRestrictions::ScopedAllowWait allow_wait;
-  return event_.IsSignaled();
+PlatformThreadId SimpleThread::GetTid() const {
+  id_event_.Wait();
+  return tid_;
 }
 
 void SimpleThread::ThreadMain() {
   tid_ = PlatformThread::CurrentId();
+  id_event_.Signal();
+
   // Construct our full name of the form "name_prefix_/TID".
   std::string name(name_prefix_);
   name.push_back('/');
   name.append(IntToString(tid_));
   PlatformThread::SetName(name);
 
-  // We've initialized our new thread, signal that we're done to Start().
-  event_.Signal();
-
   Run();
 }
 
 DelegateSimpleThread::DelegateSimpleThread(Delegate* delegate,
                                            const std::string& name_prefix)
     : DelegateSimpleThread(delegate, name_prefix, Options()) {}
 
 DelegateSimpleThread::DelegateSimpleThread(Delegate* delegate,
                                            const std::string& name_prefix,
                                            const Options& options)
@@ skipping 82 matching lines @@
 
     // A NULL delegate pointer signals us to quit.
     if (!work)
       break;
 
     work->Run();
   }
 }
 
 }  // namespace base