1 | /**************************************************************************** |
2 | ** |
3 | ** Copyright (C) 2015 Konstantin Ritt <ritt.ks@gmail.com> |
4 | ** Copyright (C) 2016 The Qt Company Ltd. |
5 | ** Copyright (C) 2015 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias Koenig <tobias.koenig@kdab.com> |
6 | ** Contact: https://www.qt.io/licensing/ |
7 | ** |
8 | ** This file is part of the QtCore module of the Qt Toolkit. |
9 | ** |
10 | ** $QT_BEGIN_LICENSE:LGPL$ |
11 | ** Commercial License Usage |
12 | ** Licensees holding valid commercial Qt licenses may use this file in |
13 | ** accordance with the commercial license agreement provided with the |
14 | ** Software or, alternatively, in accordance with the terms contained in |
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17 | ** information use the contact form at https://www.qt.io/contact-us. |
18 | ** |
19 | ** GNU Lesser General Public License Usage |
20 | ** Alternatively, this file may be used under the terms of the GNU Lesser |
21 | ** General Public License version 3 as published by the Free Software |
22 | ** Foundation and appearing in the file LICENSE.LGPL3 included in the |
23 | ** packaging of this file. Please review the following information to |
24 | ** ensure the GNU Lesser General Public License version 3 requirements |
25 | ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. |
26 | ** |
27 | ** GNU General Public License Usage |
28 | ** Alternatively, this file may be used under the terms of the GNU |
29 | ** General Public License version 2.0 or (at your option) the GNU General |
30 | ** Public license version 3 or any later version approved by the KDE Free |
31 | ** Qt Foundation. The licenses are as published by the Free Software |
32 | ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 |
33 | ** included in the packaging of this file. Please review the following |
34 | ** information to ensure the GNU General Public License requirements will |
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36 | ** https://www.gnu.org/licenses/gpl-3.0.html. |
37 | ** |
38 | ** $QT_END_LICENSE$ |
39 | ** |
40 | ****************************************************************************/ |
41 | |
42 | #include "qsystemsemaphore.h" |
43 | #include "qsystemsemaphore_p.h" |
44 | |
45 | #include <qdebug.h> |
46 | #include <qfile.h> |
47 | #include <qcoreapplication.h> |
48 | |
49 | #ifdef QT_POSIX_IPC |
50 | |
51 | #ifndef QT_NO_SYSTEMSEMAPHORE |
52 | |
53 | #include <sys/types.h> |
54 | #include <fcntl.h> |
55 | #include <errno.h> |
56 | |
57 | #include "private/qcore_unix_p.h" |
58 | |
59 | // OpenBSD 4.2 doesn't define EIDRM, see BUGS section: |
60 | // http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2 |
61 | #if defined(Q_OS_OPENBSD) && !defined(EIDRM) |
62 | #define EIDRM EINVAL |
63 | #endif |
64 | |
65 | QT_BEGIN_NAMESPACE |
66 | |
67 | bool QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode) |
68 | { |
69 | if (semaphore != SEM_FAILED) |
70 | return true; // we already have a semaphore |
71 | |
72 | if (fileName.isEmpty()) { |
73 | errorString = QCoreApplication::translate("%1: key is empty" , "QSystemSemaphore" ).arg(QLatin1String("QSystemSemaphore::handle" )); |
74 | error = QSystemSemaphore::KeyError; |
75 | return false; |
76 | } |
77 | |
78 | const QByteArray semName = QFile::encodeName(fileName); |
79 | |
80 | // Always try with O_EXCL so we know whether we created the semaphore. |
81 | int oflag = O_CREAT | O_EXCL; |
82 | for (int tryNum = 0, maxTries = 1; tryNum < maxTries; ++tryNum) { |
83 | do { |
84 | semaphore = ::sem_open(semName.constData(), oflag, 0600, initialValue); |
85 | } while (semaphore == SEM_FAILED && errno == EINTR); |
86 | if (semaphore == SEM_FAILED && errno == EEXIST) { |
87 | if (mode == QSystemSemaphore::Create) { |
88 | if (::sem_unlink(semName.constData()) == -1 && errno != ENOENT) { |
89 | setErrorString(QLatin1String("QSystemSemaphore::handle (sem_unlink)" )); |
90 | return false; |
91 | } |
92 | // Race condition: the semaphore might be recreated before |
93 | // we call sem_open again, so we'll retry several times. |
94 | maxTries = 3; |
95 | } else { |
96 | // Race condition: if it no longer exists at the next sem_open |
97 | // call, we won't realize we created it, so we'll leak it later. |
98 | oflag &= ~O_EXCL; |
99 | maxTries = 2; |
100 | } |
101 | } else { |
102 | break; |
103 | } |
104 | } |
105 | |
106 | if (semaphore == SEM_FAILED) { |
107 | setErrorString(QLatin1String("QSystemSemaphore::handle" )); |
108 | return false; |
109 | } |
110 | |
111 | createdSemaphore = (oflag & O_EXCL) != 0; |
112 | |
113 | return true; |
114 | } |
115 | |
116 | void QSystemSemaphorePrivate::cleanHandle() |
117 | { |
118 | if (semaphore != SEM_FAILED) { |
119 | if (::sem_close(semaphore) == -1) { |
120 | setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_close)" )); |
121 | #if defined QSYSTEMSEMAPHORE_DEBUG |
122 | qDebug("QSystemSemaphore::cleanHandle sem_close failed." ); |
123 | #endif |
124 | } |
125 | semaphore = SEM_FAILED; |
126 | } |
127 | |
128 | if (createdSemaphore) { |
129 | if (::sem_unlink(QFile::encodeName(fileName).constData()) == -1 && errno != ENOENT) { |
130 | setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_unlink)" )); |
131 | #if defined QSYSTEMSEMAPHORE_DEBUG |
132 | qDebug("QSystemSemaphore::cleanHandle sem_unlink failed." ); |
133 | #endif |
134 | } |
135 | createdSemaphore = false; |
136 | } |
137 | } |
138 | |
139 | bool QSystemSemaphorePrivate::modifySemaphore(int count) |
140 | { |
141 | if (!handle()) |
142 | return false; |
143 | |
144 | if (count > 0) { |
145 | int cnt = count; |
146 | do { |
147 | if (::sem_post(semaphore) == -1) { |
148 | setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_post)" )); |
149 | #if defined QSYSTEMSEMAPHORE_DEBUG |
150 | qDebug("QSystemSemaphore::modify sem_post failed %d %d" , count, errno); |
151 | #endif |
152 | // rollback changes to preserve the SysV semaphore behavior |
153 | for ( ; cnt < count; ++cnt) { |
154 | int res; |
155 | EINTR_LOOP(res, ::sem_wait(semaphore)); |
156 | } |
157 | return false; |
158 | } |
159 | --cnt; |
160 | } while (cnt > 0); |
161 | } else { |
162 | int res; |
163 | EINTR_LOOP(res, ::sem_wait(semaphore)); |
164 | if (res == -1) { |
165 | // If the semaphore was removed be nice and create it and then modifySemaphore again |
166 | if (errno == EINVAL || errno == EIDRM) { |
167 | semaphore = SEM_FAILED; |
168 | return modifySemaphore(count); |
169 | } |
170 | setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_wait)" )); |
171 | #if defined QSYSTEMSEMAPHORE_DEBUG |
172 | qDebug("QSystemSemaphore::modify sem_wait failed %d %d" , count, errno); |
173 | #endif |
174 | return false; |
175 | } |
176 | } |
177 | |
178 | clearError(); |
179 | return true; |
180 | } |
181 | |
182 | QT_END_NAMESPACE |
183 | |
184 | #endif // QT_NO_SYSTEMSEMAPHORE |
185 | |
186 | #endif // QT_POSIX_IPC |
187 | |