Introduce struct Mutex and ConditionVariable

To mimics C++11 std::mutex and std::condition_variable,
also rename locks and condition variables to be more
uniform across the classes.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/search.cpp

@@ -819,7 +819,7 @@ split_point_start: // At split points actual search starts from here
       if (SpNode)
       {
           moveCount = ++sp->moveCount;
-          lock_release(sp->lock);
+          sp->mutex.unlock();
       }
       else
           moveCount++;
@@ -885,7 +885,7 @@ split_point_start: // At split points actual search starts from here
               && (!threatMove || !connected_threat(pos, move, threatMove)))
           {
               if (SpNode)
-                  lock_grab(sp->lock);
+                  sp->mutex.lock();
 
               continue;
           }
@@ -900,7 +900,7 @@ split_point_start: // At split points actual search starts from here
           if (futilityValue < beta)
           {
               if (SpNode)
-                  lock_grab(sp->lock);
+                  sp->mutex.lock();
 
               continue;
           }
@@ -910,7 +910,7 @@ split_point_start: // At split points actual search starts from here
               && pos.see_sign(move) < 0)
           {
               if (SpNode)
-                  lock_grab(sp->lock);
+                  sp->mutex.lock();
 
               continue;
           }
@@ -974,7 +974,7 @@ split_point_start: // At split points actual search starts from here
       // Step 18. Check for new best move
       if (SpNode)
       {
-          lock_grab(sp->lock);
+          sp->mutex.lock();
           bestValue = sp->bestValue;
           alpha = sp->alpha;
       }
@@ -1670,12 +1670,12 @@ void Thread::idle_loop() {
           }
 
           // Grab the lock to avoid races with Thread::wake_up()
-          lock_grab(sleepLock);
+          mutex.lock();
 
           // If we are master and all slaves have finished don't go to sleep
           if (sp_master && !sp_master->slavesMask)
           {
-              lock_release(sleepLock);
+              mutex.unlock();
               break;
           }
 
@@ -1684,9 +1684,9 @@ void Thread::idle_loop() {
           // in the meanwhile, allocated us and sent the wake_up() call before we
           // had the chance to grab the lock.
           if (do_sleep || !is_searching)
-              cond_wait(sleepCond, sleepLock);
+              sleepCondition.wait(mutex);
 
-          lock_release(sleepLock);
+          mutex.unlock();
       }
 
       // If this thread has been assigned work, launch a search
@@ -1694,12 +1694,12 @@ void Thread::idle_loop() {
       {
           assert(!do_sleep && !do_exit);
 
-          lock_grab(Threads.splitLock);
+          Threads.mutex.lock();
 
           assert(is_searching);
           SplitPoint* sp = curSplitPoint;
 
-          lock_release(Threads.splitLock);
+          Threads.mutex.unlock();
 
           Stack ss[MAX_PLY_PLUS_2];
           Position pos(*sp->pos, this);
@@ -1707,7 +1707,7 @@ void Thread::idle_loop() {
           memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
           (ss+1)->sp = sp;
 
-          lock_grab(sp->lock);
+          sp->mutex.lock();
 
           if (sp->nodeType == Root)
               search<SplitPointRoot>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
@@ -1738,7 +1738,7 @@ void Thread::idle_loop() {
           // related data in a safe way becuase it could have been released under
           // our feet by the sp master. Also accessing other Thread objects is
           // unsafe because if we are exiting there is a chance are already freed.
-          lock_release(sp->lock);
+          sp->mutex.unlock();
       }
   }
 }

src/thread.cpp

@@ -52,12 +52,6 @@ Thread::Thread(Fn fn) {
 
   do_sleep = (fn != &Thread::main_loop); // Avoid a race with start_searching()
 
-  lock_init(sleepLock);
-  cond_init(sleepCond);
-
-  for (int j = 0; j < MAX_SPLITPOINTS_PER_THREAD; j++)
-      lock_init(splitPoints[j].lock);
-
   if (!thread_create(handle, start_routine, this))
   {
       std::cerr << "Failed to create thread number " << idx << std::endl;
@@ -74,14 +68,7 @@ Thread::~Thread() {
 
   do_exit = true; // Search must be already finished
   wake_up();
-
   thread_join(handle); // Wait for thread termination
-
-  lock_destroy(sleepLock);
-  cond_destroy(sleepCond);
-
-  for (int j = 0; j < MAX_SPLITPOINTS_PER_THREAD; j++)
-      lock_destroy(splitPoints[j].lock);
 }
 
 
@@ -93,9 +80,9 @@ void Thread::timer_loop() {
 
   while (!do_exit)
   {
-      lock_grab(sleepLock);
+      mutex.lock();
-      timed_wait(sleepCond, sleepLock, maxPly ? maxPly : INT_MAX);
+      sleepCondition.wait_for(mutex, maxPly ? maxPly : INT_MAX);
-      lock_release(sleepLock);
+      mutex.unlock();
       check_time();
   }
 }
@@ -108,18 +95,18 @@ void Thread::main_loop() {
 
   while (true)
   {
-      lock_grab(sleepLock);
+      mutex.lock();
 
       do_sleep = true; // Always return to sleep after a search
       is_searching = false;
 
       while (do_sleep && !do_exit)
       {
-          cond_signal(Threads.sleepCond); // Wake up UI thread if needed
+          Threads.sleepCondition.notify_one(); // Wake up UI thread if needed
-          cond_wait(sleepCond, sleepLock);
+          sleepCondition.wait(mutex);
       }
 
-      lock_release(sleepLock);
+      mutex.unlock();
 
       if (do_exit)
           return;
@@ -136,9 +123,9 @@ void Thread::main_loop() {
 
 void Thread::wake_up() {
 
-  lock_grab(sleepLock);
+  mutex.lock();
-  cond_signal(sleepCond);
+  sleepCondition.notify_one();
-  lock_release(sleepLock);
+  mutex.unlock();
 }
 
 
@@ -153,9 +140,9 @@ void Thread::wait_for_stop_or_ponderhit() {
 
   Signals.stopOnPonderhit = true;
 
-  lock_grab(sleepLock);
+  mutex.lock();
-  while (!Signals.stop) cond_wait(sleepCond, sleepLock);
+  while (!Signals.stop) sleepCondition.wait(mutex);;
-  lock_release(sleepLock);
+  mutex.unlock();
 }
 
 
@@ -201,8 +188,6 @@ bool Thread::is_available_to(Thread* master) const {
 
 void ThreadPool::init() {
 
-  cond_init(sleepCond);
-  lock_init(splitLock);
   timer = new Thread(&Thread::timer_loop);
   threads.push_back(new Thread(&Thread::main_loop));
   read_uci_options();
@@ -217,8 +202,6 @@ ThreadPool::~ThreadPool() {
       delete threads[i];
 
   delete timer;
-  lock_destroy(splitLock);
-  cond_destroy(sleepCond);
 }
 
 
@@ -341,8 +324,8 @@ Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
   // Try to allocate available threads and ask them to start searching setting
   // is_searching flag. This must be done under lock protection to avoid concurrent
   // allocation of the same slave by another master.
-  lock_grab(sp.lock);
+  sp.mutex.lock();
-  lock_grab(splitLock);
+  mutex.lock();
 
   for (size_t i = 0; i < size() && !Fake; ++i)
       if (threads[i]->is_available_to(master))
@@ -360,8 +343,8 @@ Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
 
   master->splitPointsCnt++;
 
-  lock_release(splitLock);
+  mutex.unlock();
-  lock_release(sp.lock);
+  sp.mutex.unlock();
 
   // Everything is set up. The master thread enters the idle loop, from which
   // it will instantly launch a search, because its is_searching flag is set.
@@ -379,8 +362,8 @@ Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
   // We have returned from the idle loop, which means that all threads are
   // finished. Note that setting is_searching and decreasing splitPointsCnt is
   // done under lock protection to avoid a race with Thread::is_available_to().
-  lock_grab(sp.lock); // To protect sp.nodes
+  sp.mutex.lock(); // To protect sp.nodes
-  lock_grab(splitLock);
+  mutex.lock();
 
   master->is_searching = true;
   master->splitPointsCnt--;
@@ -388,8 +371,8 @@ Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
   pos.set_nodes_searched(pos.nodes_searched() + sp.nodes);
   *bestMove = sp.bestMove;
 
-  lock_release(splitLock);
+  mutex.unlock();
-  lock_release(sp.lock);
+  sp.mutex.unlock();
 
   return sp.bestValue;
 }
@@ -404,10 +387,10 @@ template Value ThreadPool::split<true>(Position&, Stack*, Value, Value, Value, M
 
 void ThreadPool::set_timer(int msec) {
 
-  lock_grab(timer->sleepLock);
+  timer->mutex.lock();
   timer->maxPly = msec;
-  cond_signal(timer->sleepCond); // Wake up and restart the timer
+  timer->sleepCondition.notify_one(); // Wake up and restart the timer
-  lock_release(timer->sleepLock);
+  timer->mutex.unlock();
 }
 
 
@@ -417,10 +400,10 @@ void ThreadPool::set_timer(int msec) {
 void ThreadPool::wait_for_search_finished() {
 
   Thread* t = main_thread();
-  lock_grab(t->sleepLock);
+  t->mutex.lock();
-  cond_signal(t->sleepCond); // In case is waiting for stop or ponderhit
+  t->sleepCondition.notify_one(); // In case is waiting for stop or ponderhit
-  while (!t->do_sleep) cond_wait(sleepCond, t->sleepLock);
+  while (!t->do_sleep) sleepCondition.wait(t->mutex);
-  lock_release(t->sleepLock);
+  t->mutex.unlock();
 }
 
 

src/thread.h

@@ -31,6 +31,31 @@
 const int MAX_THREADS = 32;
 const int MAX_SPLITPOINTS_PER_THREAD = 8;
 
+struct Mutex {
+  Mutex() { lock_init(l); }
+ ~Mutex() { lock_destroy(l); }
+
+  void lock() { lock_grab(l); }
+  void unlock() { lock_release(l); }
+
+private:
+  friend struct ConditionVariable;
+
+  Lock l;
+};
+
+struct ConditionVariable {
+  ConditionVariable() { cond_init(c); }
+ ~ConditionVariable() { cond_destroy(c); }
+
+  void wait(Mutex& m) { cond_wait(c, m.l); }
+  void wait_for(Mutex& m, int ms) { timed_wait(c, m.l, ms); }
+  void notify_one() { cond_signal(c); }
+
+private:
+  WaitCondition c;
+};
+
 class Thread;
 
 struct SplitPoint {
@@ -49,7 +74,7 @@ struct SplitPoint {
   SplitPoint* parent;
 
   // Shared data
-  Lock lock;
+  Mutex mutex;
   volatile uint64_t slavesMask;
   volatile int64_t nodes;
   volatile Value alpha;
@@ -86,8 +111,8 @@ public:
   PawnTable pawnTable;
   size_t idx;
   int maxPly;
-  Lock sleepLock;
+  Mutex mutex;
-  WaitCondition sleepCond;
+  ConditionVariable sleepCondition;
   NativeHandle handle;
   Fn start_fn;
   SplitPoint* volatile curSplitPoint;
@@ -106,7 +131,7 @@ class ThreadPool {
 
 public:
   void init(); // No c'tor, Threads object is global and engine shall be fully initialized
-  ~ThreadPool();
+ ~ThreadPool();
 
   Thread& operator[](size_t id) { return *threads[id]; }
   bool use_sleeping_threads() const { return useSleepingThreads; }
@@ -131,8 +156,8 @@ private:
 
   std::vector<Thread*> threads;
   Thread* timer;
-  Lock splitLock;
+  Mutex mutex;
-  WaitCondition sleepCond;
+  ConditionVariable sleepCondition;
   Depth minimumSplitDepth;
   int maxThreadsPerSplitPoint;
   bool useSleepingThreads;