1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
// 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__
|
