Add |joinable| to Thread::Options

base/threading/thread.cc

Index: base/threading/thread.cc
diff --git a/base/threading/thread.cc b/base/threading/thread.cc
index 98610a63c09875878ffceca6417d7af16980ca89..f73113a6353929ab42ebd1d5d3e50acc33f001d4 100644
--- a/base/threading/thread.cc
+++ b/base/threading/thread.cc
@@ -8,6 +8,7 @@
 #include "base/bind_helpers.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
+#include "base/logging.h"
 #include "base/run_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
@@ -28,7 +29,7 @@ namespace {
 // because its Stop method was called.  This allows us to catch cases where
 // MessageLoop::QuitWhenIdle() is called directly, which is unexpected when
 // using a Thread to setup and run a MessageLoop.
-base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool =
+base::LazyInstance<base::ThreadLocalBoolean>::Leaky lazy_tls_bool =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
@@ -57,6 +58,10 @@ Thread::Thread(const std::string& name)
 
 Thread::~Thread() {
   Stop();
+
+  // ThreadMain() must have returned before this Thread instance is destroyed
+  // or use-after-frees could ensue.
+  DCHECK(!thread_main_exited_.get() || thread_main_exited_->IsSet());

[danakj, 2016/07/28 19:07:40]

no .get()

[gab, 2016/07/28 21:40:15]

I intentionally added the .get()'s here and below because

DCHECK(!thread_main_exited_ || thread_main_exited_->IsSet());

felt ackward (i.e. "not foo or foo is set" sounds like testing opposites...).

 }
 
 bool Thread::Start() {
@@ -74,6 +79,8 @@ bool Thread::StartWithOptions(const Options& options) {
   DCHECK(owning_sequence_checker_.CalledOnValidSequencedThread());
   DCHECK(!message_loop_);
   DCHECK(!IsRunning());
+  DCHECK(!stopping_) << "Starting a non-joinable thread a second time? That's "
+                     << "not allowed!";
 #if defined(OS_WIN)
   DCHECK((com_status_ != STA) ||
       (options.message_loop_type == MessageLoop::TYPE_UI));
@@ -83,6 +90,14 @@ bool Thread::StartWithOptions(const Options& options) {
   id_event_.Reset();
   id_ = kInvalidThreadId;
 
+  if (!thread_main_exited_.get()) {

[danakj, 2016/07/28 19:07:40]

no .get()

[gab, 2016/07/28 21:40:15]

Similarly here:

if (!thread_main_exited_)

feels like it's testing a boolean whereas the absence of the pointer means the
opposite. So I feel like the .get() makes this more obvious and draws attention
to the comment on the member variable explaining it.

+    thread_main_exited_.reset(new AtomicFlag);
+  } else {
+    // It's safe to reset |thread_main_exited_| on sequence when the underlying
+    // thread isn't running.
+    thread_main_exited_->UnsafeReset();
+  }
+
   SetThreadWasQuitProperly(false);
 
   MessageLoop::Type type = options.message_loop_type;
@@ -100,8 +115,13 @@ bool Thread::StartWithOptions(const Options& options) {
   // fixed).
   {
     AutoLock lock(thread_lock_);
-    if (!PlatformThread::CreateWithPriority(options.stack_size, this, &thread_,
-                                            options.priority)) {
+    bool success =
+        options.joinable
+            ? PlatformThread::CreateWithPriority(options.stack_size, this,
+                                                 &thread_, options.priority)
+            : PlatformThread::CreateNonJoinableWithPriority(
+                  options.stack_size, this, options.priority);
+    if (!success) {
       DLOG(ERROR) << "failed to create thread";
       message_loop_ = nullptr;
       return false;
@@ -141,11 +161,12 @@ void Thread::Stop() {
   // DCHECK(owning_sequence_checker_.CalledOnValidSequencedThread());
   AutoLock lock(thread_lock_);
 
+  StopSoon();
+
+  // Can't join if the |thread_| is either already gone or is non-joinable.
   if (thread_.is_null())
     return;
 
-  StopSoon();
-
   // Wait for the thread to exit.
   //
   // TODO(darin): Unfortunately, we need to keep |message_loop_| around until
@@ -170,6 +191,16 @@ void Thread::StopSoon() {
     return;
 
   stopping_ = true;
+
+  if (using_external_message_loop_) {
+    // Setting |stopping_| to true above should have been sufficient for this
+    // thread to be considered "stopped" per it having never set its |running_|
+    // bit by lack of its own ThreadMain.
+    DCHECK(!IsRunning());
+    message_loop_ = nullptr;
+    return;
+  }
+
   task_runner()->PostTask(
       FROM_HERE, base::Bind(&Thread::ThreadQuitHelper, Unretained(this)));
 }
@@ -219,6 +250,18 @@ bool Thread::GetThreadWasQuitProperly() {
   return quit_properly;
 }
 
+void Thread::SetMessageLoop(MessageLoop* message_loop) {
+  DCHECK(owning_sequence_checker_.CalledOnValidSequencedThread());
+
+  // Setting |message_loop_| should suffice for this thread to be considered
+  // as "running", until Stop() is invoked.
+  DCHECK(!IsRunning());
+  message_loop_ = message_loop;
+  DCHECK(IsRunning());
+
+  using_external_message_loop_ = true;
+}
+
 void Thread::ThreadMain() {
   // First, make GetThreadId() available to avoid deadlocks. It could be called
   // any place in the following thread initialization code.
@@ -282,6 +325,8 @@ void Thread::ThreadMain() {
   // (The message loop is destructed at the end of this block)
   message_loop_ = nullptr;
   run_loop_ = nullptr;
+
+  thread_main_exited_->Set();
 }
 
 void Thread::ThreadQuitHelper() {