Update PlatformThread to support a couple of new properties.

- name(): Returns the name of the thread (useful for debugging).
- GetThreadRef(): Returns the ID of the worker thread (also useful for debugging).
- QueueApc(): This is a Windows-only, protected function that allows derived classes on Windows to queue APCs to the worker thread.

NOTRY=true
(using notry since the patch has already passed the trybots and the cq is currently stalled)

Review URL: https://codereview.webrtc.org/1908373002

Cr-Commit-Position: refs/heads/master@{#12472}

webrtc/base/platform_thread.cc

@@ -99,7 +99,8 @@ PlatformThread::PlatformThread(ThreadRunFunction func,
       name_(thread_name ? thread_name : "webrtc"),
 #if defined(WEBRTC_WIN)
       stop_(false),
-      thread_(NULL) {
+      thread_(NULL),
+      thread_id_(0) {
 #else
       stop_event_(false, false),
       thread_(0) {
@@ -112,6 +113,7 @@ PlatformThread::~PlatformThread() {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
 #if defined(WEBRTC_WIN)
   RTC_DCHECK(!thread_);
+  RTC_DCHECK(!thread_id_);
 #endif  // defined(WEBRTC_WIN)
 }
 
@@ -136,10 +138,10 @@ void PlatformThread::Start() {
   // See bug 2902 for background on STACK_SIZE_PARAM_IS_A_RESERVATION.
   // Set the reserved stack stack size to 1M, which is the default on Windows
   // and Linux.
-  DWORD thread_id;
   thread_ = ::CreateThread(NULL, 1024 * 1024, &StartThread, this,
-                           STACK_SIZE_PARAM_IS_A_RESERVATION, &thread_id);
+                           STACK_SIZE_PARAM_IS_A_RESERVATION, &thread_id_);
   RTC_CHECK(thread_) << "CreateThread failed";
+  RTC_DCHECK(thread_id_);
 #else
   ThreadAttributes attr;
   // Set the stack stack size to 1M.
@@ -157,6 +159,14 @@ bool PlatformThread::IsRunning() const {
 #endif  // defined(WEBRTC_WIN)
 }
 
+PlatformThreadRef PlatformThread::GetThreadRef() const {
+#if defined(WEBRTC_WIN)
+  return thread_id_;
+#else
+  return thread_;
+#endif  // defined(WEBRTC_WIN)
+}
+
 void PlatformThread::Stop() {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   if (!IsRunning())
@@ -164,10 +174,13 @@ void PlatformThread::Stop() {
 
 #if defined(WEBRTC_WIN)
   // Set stop_ to |true| on the worker thread.
-  QueueUserAPC(&RaiseFlag, thread_, reinterpret_cast<ULONG_PTR>(&stop_));
+  bool queued = QueueAPC(&RaiseFlag, reinterpret_cast<ULONG_PTR>(&stop_));
+  // Queuing the APC can fail if the thread is being terminated.
+  RTC_CHECK(queued || GetLastError() == ERROR_GEN_FAILURE);
   WaitForSingleObject(thread_, INFINITE);
   CloseHandle(thread_);
   thread_ = nullptr;
+  thread_id_ = 0;
 #else
   stop_event_.Set();
   RTC_CHECK_EQ(0, pthread_join(thread_, nullptr));
@@ -247,4 +260,13 @@ bool PlatformThread::SetPriority(ThreadPriority priority) {
 #endif  // defined(WEBRTC_WIN)
 }
 
+#if defined(WEBRTC_WIN)
+bool PlatformThread::QueueAPC(PAPCFUNC function, ULONG_PTR data) {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  RTC_DCHECK(IsRunning());
+
+  return QueueUserAPC(function, thread_, data) != FALSE;
+}
+#endif
+
 }  // namespace rtc

webrtc/base/platform_thread.h

@@ -59,18 +59,30 @@ class PlatformThread {
   PlatformThread(ThreadRunFunction func, void* obj, const char* thread_name);
   virtual ~PlatformThread();
 
+  const std::string& name() const { return name_; }
+
   // Spawns a thread and tries to set thread priority according to the priority
   // from when CreateThread was called.
   void Start();
 
   bool IsRunning() const;
 
+  // Returns an identifier for the worker thread that can be used to do
+  // thread checks.
+  PlatformThreadRef GetThreadRef() const;
+
   // Stops (joins) the spawned thread.
   void Stop();
 
   // Set the priority of the thread. Must be called when thread is running.
   bool SetPriority(ThreadPriority priority);
 
+ protected:
+#if defined(WEBRTC_WIN)
+  // Exposed to derived classes to allow for special cases specific to Windows.
+  bool QueueAPC(PAPCFUNC apc_function, ULONG_PTR data);
+#endif
+
  private:
   void Run();
 
@@ -85,6 +97,7 @@ class PlatformThread {
 
   bool stop_;
   HANDLE thread_;
+  DWORD thread_id_;
 #else
   static void* StartThread(void* param);
 

webrtc/base/platform_thread_unittest.cc

@@ -14,31 +14,47 @@
 #include "webrtc/base/scoped_ptr.h"
 #include "webrtc/system_wrappers/include/sleep.h"
 
-namespace webrtc {
-
+namespace rtc {
+namespace {
 // Function that does nothing, and reports success.
 bool NullRunFunction(void* obj) {
-  SleepMs(0);  // Hand over timeslice, prevents busy looping.
+  webrtc::SleepMs(0);  // Hand over timeslice, prevents busy looping.
   return true;
 }
 
-TEST(PlatformThreadTest, StartStop) {
-  rtc::PlatformThread thread(&NullRunFunction, nullptr, "PlatformThreadTest");
-  thread.Start();
-  thread.Stop();
-}
-
 // Function that sets a boolean.
 bool SetFlagRunFunction(void* obj) {
   bool* obj_as_bool = static_cast<bool*>(obj);
   *obj_as_bool = true;
-  SleepMs(0);  // Hand over timeslice, prevents busy looping.
+  webrtc::SleepMs(0);  // Hand over timeslice, prevents busy looping.
   return true;
 }
+}  // namespace
+
+TEST(PlatformThreadTest, StartStop) {
+  PlatformThread thread(&NullRunFunction, nullptr, "PlatformThreadTest");
+  EXPECT_TRUE(thread.name() == "PlatformThreadTest");
+  EXPECT_TRUE(thread.GetThreadRef() == 0);
+  thread.Start();
+  EXPECT_TRUE(thread.GetThreadRef() != 0);
+  thread.Stop();
+  EXPECT_TRUE(thread.GetThreadRef() == 0);
+}
+
+TEST(PlatformThreadTest, StartStop2) {
+  PlatformThread thread1(&NullRunFunction, nullptr, "PlatformThreadTest1");
+  PlatformThread thread2(&NullRunFunction, nullptr, "PlatformThreadTest2");
+  EXPECT_TRUE(thread1.GetThreadRef() == thread2.GetThreadRef());
+  thread1.Start();
+  thread2.Start();
+  EXPECT_TRUE(thread1.GetThreadRef() != thread2.GetThreadRef());
+  thread2.Stop();
+  thread1.Stop();
+}
 
 TEST(PlatformThreadTest, RunFunctionIsCalled) {
   bool flag = false;
-  rtc::PlatformThread thread(&SetFlagRunFunction, &flag, "RunFunctionIsCalled");
+  PlatformThread thread(&SetFlagRunFunction, &flag, "RunFunctionIsCalled");
   thread.Start();
 
   // At this point, the flag may be either true or false.
@@ -47,5 +63,4 @@ TEST(PlatformThreadTest, RunFunctionIsCalled) {
   // We expect the thread to have run at least once.
   EXPECT_TRUE(flag);
 }
-
-}  // namespace webrtc
+}  // rtc