initial commit, 4.5 stable

thirdparty/embree/common/sys/mutex.h

@@ -0,0 +1,104 @@
+// Copyright 2009-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "platform.h"
+#include "intrinsics.h"
+#include "atomic.h"
+
+#define CPU_CACHELINE_SIZE 64
+namespace embree
+{
+  /*! system mutex */
+  class MutexSys {
+    friend struct ConditionImplementation;
+  public:
+    MutexSys();
+    ~MutexSys();
+
+  private:
+    MutexSys (const MutexSys& other) DELETED; // do not implement
+    MutexSys& operator= (const MutexSys& other) DELETED; // do not implement
+
+  public:
+    void lock();
+    bool try_lock();
+    void unlock();
+
+  protected:
+    void* mutex;
+  };
+
+  /*! spinning mutex */
+  class SpinLock
+  {
+  public:
+ 
+    SpinLock ()
+      : flag(false) {}
+
+    __forceinline bool isLocked() {
+      return flag.load();
+    }
+
+    __forceinline void lock()
+    {
+      while (true) 
+      {
+        while (flag.load()) 
+        {
+          _mm_pause(); 
+          _mm_pause();
+        }
+        
+        bool expected = false;
+        if (flag.compare_exchange_strong(expected,true,std::memory_order_acquire))
+          break;
+      }
+    }
+    
+    __forceinline bool try_lock()
+    {
+      bool expected = false;
+      if (flag.load() != expected) {
+        return false;
+      }
+      return flag.compare_exchange_strong(expected,true,std::memory_order_acquire);
+    }
+
+    __forceinline void unlock() {
+      flag.store(false,std::memory_order_release);
+    }
+    
+    __forceinline void wait_until_unlocked() 
+    {
+      while(flag.load())
+      {
+        _mm_pause(); 
+        _mm_pause();
+      }
+    }
+
+  public:
+    atomic<bool> flag;
+  };
+
+  class PaddedSpinLock : public SpinLock
+  {
+  private:
+    MAYBE_UNUSED char padding[CPU_CACHELINE_SIZE - sizeof(SpinLock)];
+  };
+  /*! safe mutex lock and unlock helper */
+  template<typename Mutex> class Lock {
+  public:
+    Lock (Mutex& mutex) : mutex(mutex), locked(true) { mutex.lock(); }
+    Lock (Mutex& mutex, bool locked) : mutex(mutex), locked(locked) {}
+    ~Lock() { if (locked) mutex.unlock(); }
+    __forceinline void lock() { assert(!locked); locked = true; mutex.lock(); }
+    __forceinline bool isLocked() const { return locked; }
+  protected:
+    Mutex& mutex;
+    bool locked;
+  };
+}