// Copyright (c) 2005, 2006, Google Inc. // Copyright (c) 2010, Patrick Gansterer <paroga@paroga.com> // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // * Redistributions in binary form must reproduce the above // copyright notice, this list of conditions and the following disclaimer // in the documentation and/or other materials provided with the // distribution. // * Neither the name of Google Inc. nor the names of its // contributors may be used to endorse or promote products derived from // this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. // --- // Author: Sanjay Ghemawat <opensource@google.com> #ifndef TCMALLOC_INTERNAL_SPINLOCK_H__ #define TCMALLOC_INTERNAL_SPINLOCK_H__ #include <wtf/Atomics.h> #if OS(UNIX) #include <sched.h> #endif #if ENABLE(COMPARE_AND_SWAP) static void TCMalloc_SlowLock(unsigned* lockword); // The following is a struct so that it can be initialized at compile time struct TCMalloc_SpinLock { void Lock() { if (!WTF::weakCompareAndSwap(&lockword_, 0, 1)) TCMalloc_SlowLock(&lockword_); WTF::memoryBarrierAfterLock(); } void Unlock() { WTF::memoryBarrierBeforeUnlock(); lockword_ = 0; } // Report if we think the lock can be held by this thread. // When the lock is truly held by the invoking thread // we will always return true. // Indended to be used as CHECK(lock.IsHeld()); bool IsHeld() const { return lockword_ != 0; } void Init() { lockword_ = 0; } void Finalize() { } unsigned lockword_; }; #define SPINLOCK_INITIALIZER { 0 } static void TCMalloc_SlowLock(unsigned* lockword) { do { #if OS(WINDOWS) Sleep(0); #else sched_yield(); #endif } while (!WTF::weakCompareAndSwap(lockword, 0, 1)); } #else #include <pthread.h> // Portable version struct TCMalloc_SpinLock { pthread_mutex_t private_lock_; inline void Init() { if (pthread_mutex_init(&private_lock_, NULL) != 0) CRASH(); } inline void Finalize() { if (pthread_mutex_destroy(&private_lock_) != 0) CRASH(); } inline void Lock() { if (pthread_mutex_lock(&private_lock_) != 0) CRASH(); } inline void Unlock() { if (pthread_mutex_unlock(&private_lock_) != 0) CRASH(); } bool IsHeld() { if (pthread_mutex_trylock(&private_lock_)) return true; Unlock(); return false; } }; #define SPINLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER } #endif // Corresponding locker object that arranges to acquire a spinlock for // the duration of a C++ scope. class TCMalloc_SpinLockHolder { private: TCMalloc_SpinLock* lock_; public: inline explicit TCMalloc_SpinLockHolder(TCMalloc_SpinLock* l) : lock_(l) { l->Lock(); } inline ~TCMalloc_SpinLockHolder() { lock_->Unlock(); } }; // Short-hands for convenient use by tcmalloc.cc typedef TCMalloc_SpinLock SpinLock; typedef TCMalloc_SpinLockHolder SpinLockHolder; #endif // TCMALLOC_INTERNAL_SPINLOCK_H__