1 // Copyright (c) 2005, 2006, Google Inc.
2 // Copyright (c) 2010, Patrick Gansterer <paroga@paroga.com>
3 // All rights reserved.
5 // Redistribution and use in source and binary forms, with or without
6 // modification, are permitted provided that the following conditions are
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19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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32 // Author: Sanjay Ghemawat <opensource@google.com>
34 #ifndef TCMALLOC_INTERNAL_SPINLOCK_H__
35 #define TCMALLOC_INTERNAL_SPINLOCK_H__
37 #include <wtf/Atomics.h>
42 #if ENABLE(COMPARE_AND_SWAP)
44 static void TCMalloc_SlowLock(unsigned* lockword);
46 // The following is a struct so that it can be initialized at compile time
47 struct TCMalloc_SpinLock {
49 if (!WTF::weakCompareAndSwap(&lockword_, 0, 1))
50 TCMalloc_SlowLock(&lockword_);
51 WTF::memoryBarrierAfterLock();
55 WTF::memoryBarrierBeforeUnlock();
59 // Report if we think the lock can be held by this thread.
60 // When the lock is truly held by the invoking thread
61 // we will always return true.
62 // Indended to be used as CHECK(lock.IsHeld());
64 return lockword_ != 0;
67 void Init() { lockword_ = 0; }
73 #define SPINLOCK_INITIALIZER { 0 }
75 static void TCMalloc_SlowLock(unsigned* lockword) {
82 } while (!WTF::weakCompareAndSwap(lockword, 0, 1));
90 struct TCMalloc_SpinLock {
91 pthread_mutex_t private_lock_;
94 if (pthread_mutex_init(&private_lock_, NULL) != 0) CRASH();
96 inline void Finalize() {
97 if (pthread_mutex_destroy(&private_lock_) != 0) CRASH();
100 if (pthread_mutex_lock(&private_lock_) != 0) CRASH();
102 inline void Unlock() {
103 if (pthread_mutex_unlock(&private_lock_) != 0) CRASH();
106 if (pthread_mutex_trylock(&private_lock_))
114 #define SPINLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
118 // Corresponding locker object that arranges to acquire a spinlock for
119 // the duration of a C++ scope.
120 class TCMalloc_SpinLockHolder {
122 TCMalloc_SpinLock* lock_;
124 inline explicit TCMalloc_SpinLockHolder(TCMalloc_SpinLock* l)
125 : lock_(l) { l->Lock(); }
126 inline ~TCMalloc_SpinLockHolder() { lock_->Unlock(); }
129 // Short-hands for convenient use by tcmalloc.cc
130 typedef TCMalloc_SpinLock SpinLock;
131 typedef TCMalloc_SpinLockHolder SpinLockHolder;
133 #endif // TCMALLOC_INTERNAL_SPINLOCK_H__