Use acquire() and release() for spinlocks

[stockfish] / src / thread.h

diff --git a/src/thread.h b/src/thread.h
index ea645b4547fd878742135fdbaa4f7fd79647c14a..7932ad45f6b0e967229b6557f69858a3abd94fcf 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -32,6 +32,7 @@
 #include "pawns.h"
 #include "position.h"
 #include "search.h"
+#include "thread_win32.h"
 
 struct Thread;
 
@@ -39,9 +40,6 @@ const size_t MAX_THREADS = 128;
 const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
 const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
 
-
-/// Spinlock class wraps low level atomic operations to provide a spin lock
-
 class Spinlock {
 
   std::atomic_int lock;
@@ -49,8 +47,9 @@ class Spinlock {
 public:
   Spinlock() { lock = 1; } // Init here to workaround a bug with MSVC 2013
   void acquire() {
-    while (lock.fetch_sub(1, std::memory_order_acquire) != 1)
-        while (lock.load(std::memory_order_relaxed) <= 0) {}
+      while (lock.fetch_sub(1, std::memory_order_acquire) != 1)
+          for (int cnt = 0; lock.load(std::memory_order_relaxed) <= 0; ++cnt)
+              if (cnt >= 10000) std::this_thread::yield(); // Be nice to hyperthreading
   }
   void release() { lock.store(1, std::memory_order_release); }
 };
@@ -98,8 +97,9 @@ struct ThreadBase {
   void wait_for(volatile const bool& b);
 
   std::thread nativeThread;
-  std::mutex mutex;
-  std::condition_variable sleepCondition;
+  Mutex mutex;
+  Spinlock spinlock;
+  ConditionVariable sleepCondition;
   volatile bool exit = false;
 };
 
@@ -114,7 +114,7 @@ struct Thread : public ThreadBase {
   Thread();
   virtual void idle_loop();
   bool cutoff_occurred() const;
-  bool available_to(const Thread* master) const;
+  bool can_join(const SplitPoint* sp) const;
 
   void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
              Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
@@ -161,13 +161,12 @@ struct ThreadPool : public std::vector<Thread*> {
 
   MainThread* main() { return static_cast<MainThread*>(at(0)); }
   void read_uci_options();
-  Thread* available_slave(const Thread* master) const;
+  Thread* available_slave(const SplitPoint* sp) const;
   void wait_for_think_finished();
   void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
 
   Depth minimumSplitDepth;
-  Spinlock spinlock;
-  std::condition_variable sleepCondition;
+  ConditionVariable sleepCondition;
   TimerThread* timer;
 };