bart | c61a616 | 2009-02-08 17:42:12 +0000 | [diff] [blame] | 1 | /* |
| 2 | An example that shows how to implement the monitor synchronization concept. |
| 3 | See also http://en.wikipedia.org/wiki/Monitor_(synchronization) for more |
| 4 | information about this concept. |
| 5 | |
| 6 | ---------------------------------------------------------------- |
| 7 | |
| 8 | Notice that the following BSD-style license applies to this one |
| 9 | file (monitor_example.cpp) only. The rest of Valgrind is licensed |
| 10 | under the terms of the GNU General Public License, version 2, |
| 11 | unless otherwise indicated. See the COPYING file in the source |
| 12 | distribution for details. |
| 13 | |
| 14 | ---------------------------------------------------------------- |
| 15 | |
| 16 | This file is part of DRD, a heavyweight Valgrind tool for detecting |
| 17 | errors in multithreaded programs. |
| 18 | |
| 19 | Copyright (C) 2008-2009 Bart Van Assche. All rights reserved. |
| 20 | |
| 21 | Redistribution and use in source and binary forms, with or without |
| 22 | modification, are permitted provided that the following conditions |
| 23 | are met: |
| 24 | |
| 25 | 1. Redistributions of source code must retain the above copyright |
| 26 | notice, this list of conditions and the following disclaimer. |
| 27 | |
| 28 | 2. The origin of this software must not be misrepresented; you must |
| 29 | not claim that you wrote the original software. If you use this |
| 30 | software in a product, an acknowledgment in the product |
| 31 | documentation would be appreciated but is not required. |
| 32 | |
| 33 | 3. Altered source versions must be plainly marked as such, and must |
| 34 | not be misrepresented as being the original software. |
| 35 | |
| 36 | 4. The name of the author may not be used to endorse or promote |
| 37 | products derived from this software without specific prior written |
| 38 | permission. |
| 39 | |
| 40 | THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS |
| 41 | OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| 42 | WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 43 | ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| 44 | DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 45 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE |
| 46 | GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 47 | INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 48 | WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| 49 | NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| 50 | SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 51 | |
| 52 | ---------------------------------------------------------------- |
| 53 | |
| 54 | Notice that the above BSD-style license applies to this one |
| 55 | file (monitor_example.cpp) only. The rest of Valgrind is licensed |
| 56 | under the terms of the GNU General Public License, version 2, |
| 57 | unless otherwise indicated. See the COPYING file in the source |
| 58 | distribution for details. |
| 59 | |
| 60 | ---------------------------------------------------------------- |
| 61 | */ |
bart | e64f11d | 2008-10-05 17:37:06 +0000 | [diff] [blame] | 62 | |
| 63 | |
| 64 | #define _GNU_SOURCE 1 |
| 65 | |
| 66 | |
bart | 3eadaa0 | 2008-10-06 06:34:20 +0000 | [diff] [blame] | 67 | #include "config.h" |
bart | e64f11d | 2008-10-05 17:37:06 +0000 | [diff] [blame] | 68 | #include <cassert> |
| 69 | #include <iostream> |
| 70 | #include <pthread.h> |
| 71 | |
| 72 | |
| 73 | class Monitor |
| 74 | { |
| 75 | public: |
| 76 | Monitor() |
| 77 | : m_mutex() |
| 78 | , m_cond() |
| 79 | , m_owner() |
| 80 | , m_recursion_count() |
| 81 | { |
| 82 | pthread_mutexattr_t mutexattr; |
| 83 | pthread_mutexattr_init(&mutexattr); |
| 84 | pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_RECURSIVE); |
| 85 | pthread_mutex_init(&m_mutex, &mutexattr); |
| 86 | pthread_mutexattr_destroy(&mutexattr); |
| 87 | pthread_condattr_t condattr; |
| 88 | pthread_condattr_init(&condattr); |
bart | 3eadaa0 | 2008-10-06 06:34:20 +0000 | [diff] [blame] | 89 | #if defined(HAVE_PTHREAD_CONDATTR_SETCLOCK) |
bart | e64f11d | 2008-10-05 17:37:06 +0000 | [diff] [blame] | 90 | pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC); |
bart | 3eadaa0 | 2008-10-06 06:34:20 +0000 | [diff] [blame] | 91 | #endif |
| 92 | pthread_cond_init(&m_cond, &condattr); |
bart | e64f11d | 2008-10-05 17:37:06 +0000 | [diff] [blame] | 93 | pthread_condattr_destroy(&condattr); |
| 94 | } |
| 95 | ~Monitor() |
| 96 | { |
| 97 | assert(m_recursion_count == 0); |
| 98 | pthread_cond_destroy(&m_cond); |
| 99 | pthread_mutex_destroy(&m_mutex); |
| 100 | } |
| 101 | void lock() |
| 102 | { |
| 103 | pthread_mutex_lock(&m_mutex); |
| 104 | assert(m_recursion_count >= 0); |
| 105 | if (++m_recursion_count == 1) |
| 106 | { |
| 107 | m_owner = pthread_self(); |
| 108 | } |
| 109 | } |
| 110 | void unlock() |
| 111 | { |
| 112 | m_recursion_count--; |
| 113 | assert(m_recursion_count >= 0); |
| 114 | pthread_mutex_unlock(&m_mutex); |
| 115 | } |
| 116 | void wait() |
| 117 | { |
| 118 | assert(m_recursion_count == 1); |
| 119 | assert(m_owner == pthread_self()); |
| 120 | m_recursion_count--; |
| 121 | pthread_cond_wait(&m_cond, &m_mutex); |
| 122 | m_recursion_count++; |
| 123 | m_owner = pthread_self(); |
| 124 | } |
| 125 | void signal() |
| 126 | { |
| 127 | assert(m_recursion_count > 0); |
| 128 | pthread_cond_signal(&m_cond); |
| 129 | } |
| 130 | void broadcast_signal() |
| 131 | { |
| 132 | assert(m_recursion_count > 0); |
| 133 | pthread_cond_broadcast(&m_cond); |
| 134 | } |
| 135 | bool is_locked_by_self() |
| 136 | { |
| 137 | bool result; |
| 138 | pthread_mutex_lock(&m_mutex); |
| 139 | result = m_recursion_count > 0 && m_owner == pthread_self(); |
| 140 | pthread_mutex_unlock(&m_mutex); |
| 141 | return result; |
| 142 | } |
| 143 | |
| 144 | private: |
| 145 | Monitor(const Monitor&); |
| 146 | Monitor& operator=(const Monitor&); |
| 147 | |
| 148 | pthread_mutex_t m_mutex; |
| 149 | pthread_cond_t m_cond; |
| 150 | pthread_t m_owner; |
| 151 | int m_recursion_count; |
| 152 | }; |
| 153 | |
| 154 | |
| 155 | class ScopedLock |
| 156 | { |
| 157 | public: |
| 158 | ScopedLock(Monitor& m) |
| 159 | : m_monitor(m) |
| 160 | , m_locked(false) |
| 161 | { lock(); } |
| 162 | ~ScopedLock() |
| 163 | { if (m_locked) unlock(); } |
| 164 | void lock() |
| 165 | { assert(! m_locked); m_monitor.lock(); m_locked = true; } |
| 166 | void unlock() |
| 167 | { assert(m_locked); m_locked = false; m_monitor.unlock(); } |
| 168 | |
| 169 | private: |
| 170 | ScopedLock(const ScopedLock&); |
| 171 | ScopedLock& operator=(const ScopedLock&); |
| 172 | |
| 173 | Monitor& m_monitor; |
| 174 | bool m_locked; |
| 175 | }; |
| 176 | |
| 177 | |
| 178 | class StateVariable |
| 179 | { |
| 180 | public: |
| 181 | StateVariable() |
| 182 | : m_state() |
| 183 | { } |
| 184 | int get() |
| 185 | { |
| 186 | ScopedLock sl(m_monitor); |
| 187 | return m_state; |
| 188 | } |
| 189 | void set(const int state) |
| 190 | { |
| 191 | ScopedLock sl(m_monitor); |
| 192 | m_state = state; |
| 193 | m_monitor.signal(); |
| 194 | } |
| 195 | void wait(const int state) |
| 196 | { |
| 197 | ScopedLock sl(m_monitor); |
| 198 | while (m_state != state) |
| 199 | m_monitor.wait(); |
| 200 | } |
| 201 | |
| 202 | private: |
| 203 | Monitor m_monitor; |
| 204 | int m_state; |
| 205 | }; |
| 206 | |
| 207 | |
| 208 | static StateVariable s_sv; |
| 209 | |
| 210 | |
| 211 | static void* thread_func(void*) |
| 212 | { |
| 213 | s_sv.wait(1); |
| 214 | s_sv.set(2); |
| 215 | s_sv.wait(3); |
| 216 | s_sv.set(4); |
| 217 | return 0; |
| 218 | } |
| 219 | |
| 220 | int main(int, char**) |
| 221 | { |
| 222 | pthread_t tid; |
| 223 | pthread_create(&tid, 0, thread_func, 0); |
| 224 | s_sv.set(1); |
| 225 | s_sv.wait(2); |
| 226 | s_sv.set(3); |
| 227 | s_sv.wait(4); |
| 228 | pthread_join(tid, 0); |
| 229 | std::cerr << "Finished successfully.\n"; |
| 230 | return 0; |
| 231 | } |