blob: fd406dc0ae90348be7c27a313512bf464502cea5 (
plain) (
blame)
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
|
//===---------------------- shared_mutex.cpp ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "__config"
#ifndef _LIBCPP_HAS_NO_THREADS
#include "shared_mutex"
#if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
#pragma comment(lib, "pthread")
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
// Shared Mutex Base
__shared_mutex_base::__shared_mutex_base()
: __state_(0)
{
}
// Exclusive ownership
void
__shared_mutex_base::lock()
{
unique_lock<mutex> lk(__mut_);
while (__state_ & __write_entered_)
__gate1_.wait(lk);
__state_ |= __write_entered_;
while (__state_ & __n_readers_)
__gate2_.wait(lk);
}
bool
__shared_mutex_base::try_lock()
{
unique_lock<mutex> lk(__mut_);
if (__state_ == 0)
{
__state_ = __write_entered_;
return true;
}
return false;
}
void
__shared_mutex_base::unlock()
{
lock_guard<mutex> _(__mut_);
__state_ = 0;
__gate1_.notify_all();
}
// Shared ownership
void
__shared_mutex_base::lock_shared()
{
unique_lock<mutex> lk(__mut_);
while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
__gate1_.wait(lk);
unsigned num_readers = (__state_ & __n_readers_) + 1;
__state_ &= ~__n_readers_;
__state_ |= num_readers;
}
bool
__shared_mutex_base::try_lock_shared()
{
unique_lock<mutex> lk(__mut_);
unsigned num_readers = __state_ & __n_readers_;
if (!(__state_ & __write_entered_) && num_readers != __n_readers_)
{
++num_readers;
__state_ &= ~__n_readers_;
__state_ |= num_readers;
return true;
}
return false;
}
void
__shared_mutex_base::unlock_shared()
{
lock_guard<mutex> _(__mut_);
unsigned num_readers = (__state_ & __n_readers_) - 1;
__state_ &= ~__n_readers_;
__state_ |= num_readers;
if (__state_ & __write_entered_)
{
if (num_readers == 0)
__gate2_.notify_one();
}
else
{
if (num_readers == __n_readers_ - 1)
__gate1_.notify_one();
}
}
// Shared Timed Mutex
// These routines are here for ABI stability
shared_timed_mutex::shared_timed_mutex() : __base() {}
void shared_timed_mutex::lock() { return __base.lock(); }
bool shared_timed_mutex::try_lock() { return __base.try_lock(); }
void shared_timed_mutex::unlock() { return __base.unlock(); }
void shared_timed_mutex::lock_shared() { return __base.lock_shared(); }
bool shared_timed_mutex::try_lock_shared() { return __base.try_lock_shared(); }
void shared_timed_mutex::unlock_shared() { return __base.unlock_shared(); }
_LIBCPP_END_NAMESPACE_STD
#endif // !_LIBCPP_HAS_NO_THREADS
|
