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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
/*
* $Revision: 2583 $
*
* last checkin:
* $Author: gutwenger $
* $Date: 2012-07-12 01:02:21 +0200 (Do, 12. Jul 2012) $
***************************************************************/
/** \file
* \brief Implementation of criticial sections.
*
* \author Carsten Gutwenger
*
* \par License:
* This file is part of the Open Graph Drawing Framework (OGDF).
*
* \par
* Copyright (C)<br>
* See README.txt in the root directory of the OGDF installation for details.
*
* \par
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* Version 2 or 3 as published by the Free Software Foundation;
* see the file LICENSE.txt included in the packaging of this file
* for details.
*
* \par
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* \par
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
* \see http://www.gnu.org/copyleft/gpl.html
***************************************************************/
#ifdef _MSC_VER
#pragma once
#endif
#ifndef OGDF_CRITICAL_SECTION_H
#define OGDF_CRITICAL_SECTION_H
#if !defined(OGDF_SYSTEM_WINDOWS)
#include <pthread.h>
#include <errno.h>
#endif
#include "System.h"
namespace ogdf {
#if defined(OGDF_SYSTEM_WINDOWS)
//! Representation of a critical section.
/**
* Critical sections are used to synchronize access to resources shared by
* several threads. It can be used to protect an object or a piece of code
* allowing always one thread at a time access.
*/
class OGDF_EXPORT CriticalSection
{
public:
//! Creates a critical section object.
CriticalSection() {
InitializeCriticalSection(&m_cs);
}
//! Creates a critical section object with spin count.
/**
* The spin count determines how many times the calling thread spins
* when the critical section is unavailable, before it performs a wait.
* \remark The spin count is only used on multiprocessor systems;
* otherwise it makes no sense.
*/
explicit CriticalSection(int spinCount) {
InitializeCriticalSectionAndSpinCount(&m_cs, spinCount);
}
~CriticalSection() {
DeleteCriticalSection(&m_cs);
}
//! Enters the critical section.
void enter() {
EnterCriticalSection(&m_cs);
}
//! Tries to enter the critical section; returns true on success.
bool tryEnter() {
return (TryEnterCriticalSection(&m_cs) != 0);
}
//! Leaves the critical section.
void leave() {
LeaveCriticalSection(&m_cs);
}
private:
CRITICAL_SECTION m_cs; //!< The Windows critical section object.
};
#else
class OGDF_EXPORT CriticalSection
{
public:
CriticalSection() : m_spinCount(0) {
pthread_mutex_init(&m_mutex, NULL);
}
explicit CriticalSection(int spinCount) {
m_spinCount = (System::numberOfProcessors() >= 2) ? spinCount : 0;
int ret = pthread_mutex_init(&m_mutex, NULL);
if(ret != 0)
cout << "initialization of mutex failed: " << ret << endl;
}
~CriticalSection() {
pthread_mutex_destroy(&m_mutex);
}
void enter() {
if(m_spinCount > 0) {
for(int i = m_spinCount; i > 0; --i)
if(pthread_mutex_trylock(&m_mutex) != EBUSY)
return;
}
pthread_mutex_lock(&m_mutex);
}
bool tryEnter() {
return (pthread_mutex_trylock(&m_mutex) != EBUSY);
}
void leave() {
pthread_mutex_unlock(&m_mutex);
}
private:
pthread_mutex_t m_mutex;
int m_spinCount;
};
#endif
} // end namespace ogdf
#endif
|
