1 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
2 /* dbus-sysdeps-pthread.c Implements threads using pthreads (internal to libdbus)
4 * Copyright (C) 2002, 2003, 2006 Red Hat, Inc.
6 * Licensed under the Academic Free License version 2.1
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #include "dbus-internals.h"
25 #include "dbus-sysdeps.h"
26 #include "dbus-threads.h"
37 pthread_mutex_t lock; /**< lock protecting count field */
38 volatile int count; /**< count of how many times lock holder has recursively locked */
39 volatile pthread_t holder; /**< holder of the lock if count >0,
40 valid but arbitrary thread if count
41 has ever been >0, uninitialized memory
42 if count has never been >0 */
46 pthread_cond_t cond; /**< the condition */
49 #define DBUS_MUTEX(m) ((DBusMutex*) m)
50 #define DBUS_MUTEX_PTHREAD(m) ((DBusMutexPThread*) m)
52 #define DBUS_COND_VAR(c) ((DBusCondVar*) c)
53 #define DBUS_COND_VAR_PTHREAD(c) ((DBusCondVarPThread*) c)
56 #ifdef DBUS_DISABLE_ASSERT
57 /* (tmp != 0) is a no-op usage to silence compiler */
58 #define PTHREAD_CHECK(func_name, result_or_call) \
59 do { int tmp = (result_or_call); if (tmp != 0) {;} } while (0)
61 #define PTHREAD_CHECK(func_name, result_or_call) do { \
62 int tmp = (result_or_call); \
64 _dbus_warn_check_failed ("pthread function %s failed with %d %s in %s\n", \
65 func_name, tmp, strerror(tmp), _DBUS_FUNCTION_NAME); \
68 #endif /* !DBUS_DISABLE_ASSERT */
71 _dbus_pthread_mutex_new (void)
73 DBusMutexPThread *pmutex;
76 pmutex = dbus_new (DBusMutexPThread, 1);
80 result = pthread_mutex_init (&pmutex->lock, NULL);
82 if (result == ENOMEM || result == EAGAIN)
89 PTHREAD_CHECK ("pthread_mutex_init", result);
95 /* There's no portable way to have a "null" pthread afaik so we
96 * can't set pmutex->holder to anything sensible. We only access it
97 * once the lock is held (which means we've set it).
100 return DBUS_MUTEX (pmutex);
104 _dbus_pthread_mutex_free (DBusMutex *mutex)
106 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
108 _dbus_assert (pmutex->count == 0);
110 PTHREAD_CHECK ("pthread_mutex_destroy", pthread_mutex_destroy (&pmutex->lock));
116 _dbus_pthread_mutex_lock (DBusMutex *mutex)
118 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
119 pthread_t self = pthread_self ();
121 /* If the count is > 0 then someone had the lock, maybe us. If it is
122 * 0, then it might immediately change right after we read it,
123 * but it will be changed by another thread; i.e. if we read 0,
124 * we assume that this thread doesn't have the lock.
126 * Not 100% sure this is safe, but ... seems like it should be.
128 if (pmutex->count == 0)
130 /* We know we don't have the lock; someone may have the lock. */
132 PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
134 /* We now have the lock. Count must be 0 since it must be 0 when
135 * the lock is released by another thread, and we just now got
138 _dbus_assert (pmutex->count == 0);
140 pmutex->holder = self;
145 /* We know someone had the lock, possibly us. Thus
146 * pmutex->holder is not pointing to junk, though it may not be
147 * the lock holder anymore if the lock holder is not us. If the
148 * lock holder is us, then we definitely have the lock.
151 if (pthread_equal (pmutex->holder, self))
153 /* We already have the lock. */
154 _dbus_assert (pmutex->count > 0);
158 /* Wait for the lock */
159 PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
160 pmutex->holder = self;
161 _dbus_assert (pmutex->count == 0);
169 _dbus_pthread_mutex_unlock (DBusMutex *mutex)
171 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
173 _dbus_assert (pmutex->count > 0);
177 if (pmutex->count == 0)
178 PTHREAD_CHECK ("pthread_mutex_unlock", pthread_mutex_unlock (&pmutex->lock));
180 /* We leave pmutex->holder set to ourselves, its content is undefined if count is 0 */
184 _dbus_pthread_condvar_new (void)
186 DBusCondVarPThread *pcond;
189 pcond = dbus_new (DBusCondVarPThread, 1);
193 result = pthread_cond_init (&pcond->cond, NULL);
195 if (result == EAGAIN || result == ENOMEM)
202 PTHREAD_CHECK ("pthread_cond_init", result);
205 return DBUS_COND_VAR (pcond);
209 _dbus_pthread_condvar_free (DBusCondVar *cond)
211 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
213 PTHREAD_CHECK ("pthread_cond_destroy", pthread_cond_destroy (&pcond->cond));
219 _dbus_pthread_condvar_wait (DBusCondVar *cond,
222 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
223 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
226 _dbus_assert (pmutex->count > 0);
227 _dbus_assert (pthread_equal (pmutex->holder, pthread_self ()));
229 old_count = pmutex->count;
230 pmutex->count = 0; /* allow other threads to lock */
231 PTHREAD_CHECK ("pthread_cond_wait", pthread_cond_wait (&pcond->cond, &pmutex->lock));
232 _dbus_assert (pmutex->count == 0);
233 pmutex->count = old_count;
234 pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */
238 _dbus_pthread_condvar_wait_timeout (DBusCondVar *cond,
240 int timeout_milliseconds)
242 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
243 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
244 struct timeval time_now;
245 struct timespec end_time;
249 _dbus_assert (pmutex->count > 0);
250 _dbus_assert (pthread_equal (pmutex->holder, pthread_self ()));
252 gettimeofday (&time_now, NULL);
254 end_time.tv_sec = time_now.tv_sec + timeout_milliseconds / 1000;
255 end_time.tv_nsec = (time_now.tv_usec + (timeout_milliseconds % 1000) * 1000) * 1000;
256 if (end_time.tv_nsec > 1000*1000*1000)
258 end_time.tv_sec += 1;
259 end_time.tv_nsec -= 1000*1000*1000;
262 old_count = pmutex->count;
264 result = pthread_cond_timedwait (&pcond->cond, &pmutex->lock, &end_time);
266 if (result != ETIMEDOUT)
268 PTHREAD_CHECK ("pthread_cond_timedwait", result);
271 _dbus_assert (pmutex->count == 0);
272 pmutex->count = old_count;
273 pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */
275 /* return true if we did not time out */
276 return result != ETIMEDOUT;
280 _dbus_pthread_condvar_wake_one (DBusCondVar *cond)
282 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
284 PTHREAD_CHECK ("pthread_cond_signal", pthread_cond_signal (&pcond->cond));
288 _dbus_pthread_condvar_wake_all (DBusCondVar *cond)
290 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
292 PTHREAD_CHECK ("pthread_cond_broadcast", pthread_cond_broadcast (&pcond->cond));
295 static const DBusThreadFunctions pthread_functions =
297 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK |
298 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK |
299 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK |
300 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK |
301 DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK |
302 DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK |
303 DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK |
304 DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK |
305 DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK|
306 DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK,
307 NULL, NULL, NULL, NULL,
308 _dbus_pthread_condvar_new,
309 _dbus_pthread_condvar_free,
310 _dbus_pthread_condvar_wait,
311 _dbus_pthread_condvar_wait_timeout,
312 _dbus_pthread_condvar_wake_one,
313 _dbus_pthread_condvar_wake_all,
314 _dbus_pthread_mutex_new,
315 _dbus_pthread_mutex_free,
316 _dbus_pthread_mutex_lock,
317 _dbus_pthread_mutex_unlock
321 _dbus_threads_init_platform_specific (void)
323 return dbus_threads_init (&pthread_functions);