blob: 64b8f747eac799fdb7dcb93f995f101cacf7e2ca (
plain)
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
|
// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_LOCK_H_
#define BASE_LOCK_H_
#include "base/lock_impl.h"
// A convenient wrapper for an OS specific critical section. The only real
// intelligence in this class is in debug mode for the support for the
// AssertAcquired() method.
class Lock {
public:
#if defined(NDEBUG) // Optimized wrapper implementation
Lock() : lock_() {}
~Lock() {}
void Acquire() { lock_.Lock(); }
void Release() { lock_.Unlock(); }
// If the lock is not held, take it and return true. If the lock is already
// held by another thread, immediately return false.
bool Try() { return lock_.Try(); }
// Null implementation if not debug.
void AssertAcquired() const {}
#else
Lock();
~Lock() {}
// NOTE: Although windows critical sections support recursive locks, we do not
// allow this, and we will commonly fire a DCHECK() if a thread attempts to
// acquire the lock a second time (while already holding it).
void Acquire() {
lock_.Lock();
CheckUnheldAndMark();
}
void Release() {
CheckHeldAndUnmark();
lock_.Unlock();
}
bool Try() {
bool rv = lock_.Try();
if (rv) {
CheckUnheldAndMark();
}
return rv;
}
void AssertAcquired() const;
#endif // NDEBUG
#if defined(OS_POSIX)
// The posix implementation of ConditionVariable needs to be able
// to see our lock and tweak our debugging counters, as it releases
// and acquires locks inside of pthread_cond_{timed,}wait.
// Windows doesn't need to do this as it calls the Lock::* methods.
friend class ConditionVariable;
#endif
private:
#if !defined(NDEBUG)
// Members and routines taking care of locks assertions.
// Note that this checks for recursive locks and allows them
// if the variable is set. This is allowed by the underlying implementation
// on windows but not on Posix, so we're doing unneeded checks on Posix.
// It's worth it to share the code.
void CheckHeldAndUnmark();
void CheckUnheldAndMark();
// All private data is implicitly protected by lock_.
// Be VERY careful to only access members under that lock.
// Determines validity of owning_thread_id_. Needed as we don't have
// a null owning_thread_id_ value.
bool owned_by_thread_;
PlatformThreadId owning_thread_id_;
#endif // NDEBUG
LockImpl lock_; // Platform specific underlying lock implementation.
DISALLOW_COPY_AND_ASSIGN(Lock);
};
// A helper class that acquires the given Lock while the AutoLock is in scope.
class AutoLock {
public:
explicit AutoLock(Lock& lock) : lock_(lock) {
lock_.Acquire();
}
~AutoLock() {
lock_.AssertAcquired();
lock_.Release();
}
private:
Lock& lock_;
DISALLOW_COPY_AND_ASSIGN(AutoLock);
};
// AutoUnlock is a helper that will Release() the |lock| argument in the
// constructor, and re-Acquire() it in the destructor.
class AutoUnlock {
public:
explicit AutoUnlock(Lock& lock) : lock_(lock) {
// We require our caller to have the lock.
lock_.AssertAcquired();
lock_.Release();
}
~AutoUnlock() {
lock_.Acquire();
}
private:
Lock& lock_;
DISALLOW_COPY_AND_ASSIGN(AutoUnlock);
};
#endif // BASE_LOCK_H_
|
