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1 // Copyright (c) 2005, 2006, Google Inc. | |
2 // Copyright (c) 2010, Patrick Gansterer <paroga@paroga.com> | |
3 // All rights reserved. | |
4 // | |
5 // Redistribution and use in source and binary forms, with or without | |
6 // modification, are permitted provided that the following conditions are | |
7 // met: | |
8 // | |
9 // * Redistributions of source code must retain the above copyright | |
10 // notice, this list of conditions and the following disclaimer. | |
11 // * Redistributions in binary form must reproduce the above | |
12 // copyright notice, this list of conditions and the following disclaimer | |
13 // in the documentation and/or other materials provided with the | |
14 // distribution. | |
15 // * Neither the name of Google Inc. nor the names of its | |
16 // contributors may be used to endorse or promote products derived from | |
17 // this software without specific prior written permission. | |
18 // | |
19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
30 | |
31 // --- | |
32 // Author: Sanjay Ghemawat <opensource@google.com> | |
33 | |
34 #ifndef TCMALLOC_INTERNAL_SPINLOCK_H__ | |
35 #define TCMALLOC_INTERNAL_SPINLOCK_H__ | |
36 | |
37 #include <wtf/Atomics.h> | |
38 #if OS(UNIX) | |
39 #include <sched.h> | |
40 #endif | |
41 | |
42 #if ENABLE(COMPARE_AND_SWAP) | |
43 | |
44 static void TCMalloc_SlowLock(unsigned* lockword); | |
45 | |
46 // The following is a struct so that it can be initialized at compile time | |
47 struct TCMalloc_SpinLock { | |
48 void Lock() { | |
49 if (!WTF::weakCompareAndSwap(&lockword_, 0, 1)) | |
50 TCMalloc_SlowLock(&lockword_); | |
51 WTF::memoryBarrierAfterLock(); | |
52 } | |
53 | |
54 void Unlock() { | |
55 WTF::memoryBarrierBeforeUnlock(); | |
56 lockword_ = 0; | |
57 } | |
58 | |
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()); | |
63 bool IsHeld() const { | |
64 return lockword_ != 0; | |
65 } | |
66 | |
67 void Init() { lockword_ = 0; } | |
68 void Finalize() { } | |
69 | |
70 unsigned lockword_; | |
71 }; | |
72 | |
73 #define SPINLOCK_INITIALIZER { 0 } | |
74 | |
75 static void TCMalloc_SlowLock(unsigned* lockword) { | |
76 do { | |
77 #if OS(WINDOWS) | |
78 Sleep(0); | |
79 #else | |
80 sched_yield(); | |
81 #endif | |
82 } while (!WTF::weakCompareAndSwap(lockword, 0, 1)); | |
83 } | |
84 | |
85 #else | |
86 | |
87 #include <pthread.h> | |
88 | |
89 // Portable version | |
90 struct TCMalloc_SpinLock { | |
91 pthread_mutex_t private_lock_; | |
92 | |
93 inline void Init() { | |
94 if (pthread_mutex_init(&private_lock_, NULL) != 0) CRASH(); | |
95 } | |
96 inline void Finalize() { | |
97 if (pthread_mutex_destroy(&private_lock_) != 0) CRASH(); | |
98 } | |
99 inline void Lock() { | |
100 if (pthread_mutex_lock(&private_lock_) != 0) CRASH(); | |
101 } | |
102 inline void Unlock() { | |
103 if (pthread_mutex_unlock(&private_lock_) != 0) CRASH(); | |
104 } | |
105 bool IsHeld() { | |
106 if (pthread_mutex_trylock(&private_lock_)) | |
107 return true; | |
108 | |
109 Unlock(); | |
110 return false; | |
111 } | |
112 }; | |
113 | |
114 #define SPINLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER } | |
115 | |
116 #endif | |
117 | |
118 // Corresponding locker object that arranges to acquire a spinlock for | |
119 // the duration of a C++ scope. | |
120 class TCMalloc_SpinLockHolder { | |
121 private: | |
122 TCMalloc_SpinLock* lock_; | |
123 public: | |
124 inline explicit TCMalloc_SpinLockHolder(TCMalloc_SpinLock* l) | |
125 : lock_(l) { l->Lock(); } | |
126 inline ~TCMalloc_SpinLockHolder() { lock_->Unlock(); } | |
127 }; | |
128 | |
129 // Short-hands for convenient use by tcmalloc.cc | |
130 typedef TCMalloc_SpinLock SpinLock; | |
131 typedef TCMalloc_SpinLockHolder SpinLockHolder; | |
132 | |
133 #endif // TCMALLOC_INTERNAL_SPINLOCK_H__ | |
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