// SwiftShader Software Renderer | |
// | |
// Copyright(c) 2005-2011 TransGaming Inc. | |
// | |
// All rights reserved. No part of this software may be copied, distributed, transmitted, | |
// transcribed, stored in a retrieval system, translated into any human or computer | |
// language by any means, or disclosed to third parties without the explicit written | |
// agreement of TransGaming Inc. Without such an agreement, no rights or licenses, express | |
// or implied, including but not limited to any patent rights, are granted to you. | |
// | |
#ifndef sw_MutexLock_hpp | |
#define sw_MutexLock_hpp | |
#include "Thread.hpp" | |
namespace sw | |
{ | |
class BackoffLock | |
{ | |
public: | |
BackoffLock() | |
{ | |
mutex = 0; | |
} | |
bool attemptLock() | |
{ | |
if(!isLocked()) | |
{ | |
if(atomicExchange(&mutex, 1) == 0) | |
{ | |
return true; | |
} | |
} | |
return false; | |
} | |
void lock() | |
{ | |
int backoff = 1; | |
while(!attemptLock()) | |
{ | |
if(backoff <= 64) | |
{ | |
for(int i = 0; i < backoff; i++) | |
{ | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
nop(); | |
} | |
backoff *= 2; | |
} | |
else | |
{ | |
Thread::yield(); | |
backoff = 1; | |
} | |
}; | |
} | |
void unlock() | |
{ | |
mutex = 0; | |
} | |
bool isLocked() | |
{ | |
return mutex != 0; | |
} | |
private: | |
// Ensure that the mutex variable is on its own 64-byte cache line to avoid false sharing | |
volatile int a[16]; | |
volatile int mutex; | |
volatile int b[15]; | |
}; | |
} | |
#endif // sw_MutexLock_hpp |