Fix race while exiting

[stockfish] / src / thread.cpp

diff --git a/src/thread.cpp b/src/thread.cpp
index d674c3ab3f9872635eddd77c7b2d89c65e31cfd9..9bd7498979761942ba0b0e01f315e2c444385c26 100644 (file)
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -32,24 +32,22 @@ ThreadPool Threads; // Global object
 namespace { extern "C" {
 
  // start_routine() is the C function which is called when a new thread
- // is launched. It is a wrapper to member function pointed by start_fn.
+ // is launched. It is a wrapper to the virtual function idle_loop().
 
- long start_routine(Thread* th) { (th->*(th->start_fn))(); return 0; }
+ long start_routine(Thread* th) { th->idle_loop(); return 0; }
 
 } }
 
 
 // Thread c'tor starts a newly-created thread of execution that will call
-// the idle loop function pointed by start_fn going immediately to sleep.
+// the the virtual function idle_loop(), going immediately to sleep.
 
-Thread::Thread(Fn fn) : splitPoints() {
+Thread::Thread() : splitPoints() {
 
   is_searching = do_exit = false;
   maxPly = splitPointsCnt = 0;
   curSplitPoint = NULL;
-  start_fn = fn;
   idx = Threads.size();
-  do_sleep = true;
 
   if (!thread_create(handle, start_routine, this))
   {
@@ -59,48 +57,50 @@ Thread::Thread(Fn fn) : splitPoints() {
 }
 
 
-// Thread d'tor waits for thread termination before to return.
+// Thread d'tor waits for thread termination before to return
 
 Thread::~Thread() {
 
-  assert(do_sleep);
-
   do_exit = true; // Search must be already finished
   notify_one();
   thread_join(handle); // Wait for thread termination
 }
 
 
-// Thread::timer_loop() is where the timer thread waits maxPly milliseconds and
-// then calls check_time(). If maxPly is 0 thread sleeps until is woken up.
+// TimerThread::idle_loop() is where the timer thread waits msec milliseconds
+// and then calls check_time(). If msec is 0 thread sleeps until is woken up.
 extern void check_time();
 
-void Thread::timer_loop() {
+void TimerThread::idle_loop() {
 
   while (!do_exit)
   {
       mutex.lock();
-      while (!maxPly && !do_exit)
-          sleepCondition.wait_for(mutex, maxPly ? maxPly : INT_MAX);
+
+      if (!do_exit)
+          sleepCondition.wait_for(mutex, msec ? msec : INT_MAX);
+
       mutex.unlock();
-      check_time();
+
+      if (msec)
+          check_time();
   }
 }
 
 
-// Thread::main_loop() is where the main thread is parked waiting to be started
+// MainThread::idle_loop() is where the main thread is parked waiting to be started
 // when there is a new search. Main thread will launch all the slave threads.
 
-void Thread::main_loop() {
+void MainThread::idle_loop() {
 
   while (true)
   {
       mutex.lock();
 
-      do_sleep = true; // Always return to sleep after a search
+      is_finished = true; // Always return to sleep after a search
       is_searching = false;
 
-      while (do_sleep && !do_exit)
+      while (is_finished && !do_exit)
       {
           Threads.sleepCondition.notify_one(); // Wake up UI thread if needed
           sleepCondition.wait(mutex);
@@ -120,8 +120,7 @@ void Thread::main_loop() {
 }
 
 
-// Thread::notify_one() wakes up the thread, normally at the beginning of the
-// search or, if "sleeping threads" is used at split time.
+// Thread::notify_one() wakes up the thread, normally at split time
 
 void Thread::notify_one() {
 
@@ -183,8 +182,9 @@ bool Thread::is_available_to(Thread* master) const {
 
 void ThreadPool::init() {
 
-  timer = new Thread(&Thread::timer_loop);
-  threads.push_back(new Thread(&Thread::main_loop));
+  sleepWhileIdle = true;
+  timer = new TimerThread();
+  threads.push_back(new MainThread());
   read_uci_options();
 }
 
@@ -209,13 +209,12 @@ void ThreadPool::read_uci_options() {
 
   maxThreadsPerSplitPoint = Options["Max Threads per Split Point"];
   minimumSplitDepth       = Options["Min Split Depth"] * ONE_PLY;
-  useSleepingThreads      = Options["Use Sleeping Threads"];
   size_t requested        = Options["Threads"];
 
   assert(requested > 0);
 
   while (threads.size() < requested)
-      threads.push_back(new Thread(&Thread::idle_loop));
+      threads.push_back(new Thread());
 
   while (threads.size() > requested)
   {
@@ -301,9 +300,7 @@ Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
           sp.slavesMask |= 1ULL << i;
           threads[i]->curSplitPoint = &sp;
           threads[i]->is_searching = true; // Slave leaves idle_loop()
-
-          if (useSleepingThreads)
-              threads[i]->notify_one();
+          threads[i]->notify_one(); // Could be sleeping
 
           if (++slavesCnt + 1 >= maxThreadsPerSplitPoint) // Master is always included
               break;
@@ -320,7 +317,7 @@ Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
   // their work at this split point.
   if (slavesCnt || Fake)
   {
-      master->idle_loop();
+      master->Thread::idle_loop(); // Force a call to base class idle_loop()
 
       // In helpful master concept a master can help only a sub-tree of its split
       // point, and because here is all finished is not possible master is booked.
@@ -355,9 +352,9 @@ template Value ThreadPool::split<true>(Position&, Stack*, Value, Value, Value, M
 
 void ThreadPool::wait_for_search_finished() {
 
-  Thread* t = main_thread();
+  MainThread* t = main_thread();
   t->mutex.lock();
-  while (!t->do_sleep) sleepCondition.wait(t->mutex);
+  while (!t->is_finished) sleepCondition.wait(t->mutex);
   t->mutex.unlock();
 }
 
@@ -383,6 +380,6 @@ void ThreadPool::start_searching(const Position& pos, const LimitsType& limits,
       if (searchMoves.empty() || count(searchMoves.begin(), searchMoves.end(), ml.move()))
           RootMoves.push_back(RootMove(ml.move()));
 
-  main_thread()->do_sleep = false;
-  main_thread()->notify_one();
+  main_thread()->is_finished = false;
+  main_thread()->notify_one(); // Starts main thread
 }