1 /* -*- mode: C; c-file-style: "gnu" -*- */
2 /* dbus-sysdeps-pthread.c Implements threads using pthreads (internal to libdbus)
3 *
4 * Copyright (C) 2002, 2003, 2006 Red Hat, Inc.
5 *
6 * Licensed under the Academic Free License version 2.1
7 *
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.
12 *
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.
17 *
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 *
22 */
23
24 #include "dbus-internals.h"
25 #include "dbus-sysdeps.h"
26 #include "dbus-threads.h"
27
28 #include <sys/time.h>
29 #include <pthread.h>
30 #include <string.h>
31
32 typedef struct {
33 pthread_mutex_t lock; /**< lock protecting count field */
34 volatile int count; /**< count of how many times lock holder has recursively locked */
35 volatile pthread_t holder; /**< holder of the lock if count >0,
36 valid but arbitrary thread if count
37 has ever been >0, uninitialized memory
38 if count has never been >0 */
39 } DBusMutexPThread;
40
41 typedef struct {
42 pthread_cond_t cond; /**< the condition */
43 } DBusCondVarPThread;
44
45 #define DBUS_MUTEX(m) ((DBusMutex*) m)
46 #define DBUS_MUTEX_PTHREAD(m) ((DBusMutexPThread*) m)
47
48 #define DBUS_COND_VAR(c) ((DBusCondVar*) c)
49 #define DBUS_COND_VAR_PTHREAD(c) ((DBusCondVarPThread*) c)
50
51
52 #ifdef DBUS_DISABLE_ASSERT
53 /* (tmp != 0) is a no-op usage to silence compiler */
54 #define PTHREAD_CHECK(func_name, result_or_call) \
55 do { int tmp = (result_or_call); if (tmp != 0) {;} } while (0)
56 #else
57 #define PTHREAD_CHECK(func_name, result_or_call) do { \
58 int tmp = (result_or_call); \
59 if (tmp != 0) { \
60 _dbus_warn_check_failed ("pthread function %s failed with %d %s in %s\n", \
61 func_name, tmp, strerror(tmp), _DBUS_FUNCTION_NAME); \
62 } \
63 } while (0)
64 #endif /* !DBUS_DISABLE_ASSERT */
65
66 static DBusMutex*
_dbus_pthread_mutex_new(void)67 _dbus_pthread_mutex_new (void)
68 {
69 DBusMutexPThread *pmutex;
70 int result;
71
72 pmutex = dbus_new (DBusMutexPThread, 1);
73 if (pmutex == NULL)
74 return NULL;
75
76 result = pthread_mutex_init (&pmutex->lock, NULL);
77
78 if (result == ENOMEM || result == EAGAIN)
79 {
80 dbus_free (pmutex);
81 return NULL;
82 }
83 else
84 {
85 PTHREAD_CHECK ("pthread_mutex_init", result);
86 }
87
88 /* Only written */
89 pmutex->count = 0;
90
91 /* There's no portable way to have a "null" pthread afaik so we
92 * can't set pmutex->holder to anything sensible. We only access it
93 * once the lock is held (which means we've set it).
94 */
95
96 return DBUS_MUTEX (pmutex);
97 }
98
99 static void
_dbus_pthread_mutex_free(DBusMutex * mutex)100 _dbus_pthread_mutex_free (DBusMutex *mutex)
101 {
102 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
103
104 _dbus_assert (pmutex->count == 0);
105
106 PTHREAD_CHECK ("pthread_mutex_destroy", pthread_mutex_destroy (&pmutex->lock));
107
108 dbus_free (pmutex);
109 }
110
111 static void
_dbus_pthread_mutex_lock(DBusMutex * mutex)112 _dbus_pthread_mutex_lock (DBusMutex *mutex)
113 {
114 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
115 pthread_t self = pthread_self ();
116
117 /* If the count is > 0 then someone had the lock, maybe us. If it is
118 * 0, then it might immediately change right after we read it,
119 * but it will be changed by another thread; i.e. if we read 0,
120 * we assume that this thread doesn't have the lock.
121 *
122 * Not 100% sure this is safe, but ... seems like it should be.
123 */
124 if (pmutex->count == 0)
125 {
126 /* We know we don't have the lock; someone may have the lock. */
127
128 PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
129
130 /* We now have the lock. Count must be 0 since it must be 0 when
131 * the lock is released by another thread, and we just now got
132 * the lock.
133 */
134 _dbus_assert (pmutex->count == 0);
135
136 pmutex->holder = self;
137 pmutex->count = 1;
138 }
139 else
140 {
141 /* We know someone had the lock, possibly us. Thus
142 * pmutex->holder is not pointing to junk, though it may not be
143 * the lock holder anymore if the lock holder is not us. If the
144 * lock holder is us, then we definitely have the lock.
145 */
146
147 if (pthread_equal (pmutex->holder, self))
148 {
149 /* We already have the lock. */
150 _dbus_assert (pmutex->count > 0);
151 }
152 else
153 {
154 /* Wait for the lock */
155 PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
156 pmutex->holder = self;
157 _dbus_assert (pmutex->count == 0);
158 }
159
160 pmutex->count += 1;
161 }
162 }
163
164 static void
_dbus_pthread_mutex_unlock(DBusMutex * mutex)165 _dbus_pthread_mutex_unlock (DBusMutex *mutex)
166 {
167 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
168
169 _dbus_assert (pmutex->count > 0);
170
171 pmutex->count -= 1;
172
173 if (pmutex->count == 0)
174 PTHREAD_CHECK ("pthread_mutex_unlock", pthread_mutex_unlock (&pmutex->lock));
175
176 /* We leave pmutex->holder set to ourselves, its content is undefined if count is 0 */
177 }
178
179 static DBusCondVar *
_dbus_pthread_condvar_new(void)180 _dbus_pthread_condvar_new (void)
181 {
182 DBusCondVarPThread *pcond;
183 int result;
184
185 pcond = dbus_new (DBusCondVarPThread, 1);
186 if (pcond == NULL)
187 return NULL;
188
189 result = pthread_cond_init (&pcond->cond, NULL);
190
191 if (result == EAGAIN || result == ENOMEM)
192 {
193 dbus_free (pcond);
194 return NULL;
195 }
196 else
197 {
198 PTHREAD_CHECK ("pthread_cond_init", result);
199 }
200
201 return DBUS_COND_VAR (pcond);
202 }
203
204 static void
_dbus_pthread_condvar_free(DBusCondVar * cond)205 _dbus_pthread_condvar_free (DBusCondVar *cond)
206 {
207 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
208
209 PTHREAD_CHECK ("pthread_cond_destroy", pthread_cond_destroy (&pcond->cond));
210
211 dbus_free (pcond);
212 }
213
214 static void
_dbus_pthread_condvar_wait(DBusCondVar * cond,DBusMutex * mutex)215 _dbus_pthread_condvar_wait (DBusCondVar *cond,
216 DBusMutex *mutex)
217 {
218 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
219 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
220 int old_count;
221
222 _dbus_assert (pmutex->count > 0);
223 _dbus_assert (pthread_equal (pmutex->holder, pthread_self ()));
224
225 old_count = pmutex->count;
226 pmutex->count = 0; /* allow other threads to lock */
227 PTHREAD_CHECK ("pthread_cond_wait", pthread_cond_wait (&pcond->cond, &pmutex->lock));
228 _dbus_assert (pmutex->count == 0);
229 pmutex->count = old_count;
230 pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */
231 }
232
233 static dbus_bool_t
_dbus_pthread_condvar_wait_timeout(DBusCondVar * cond,DBusMutex * mutex,int timeout_milliseconds)234 _dbus_pthread_condvar_wait_timeout (DBusCondVar *cond,
235 DBusMutex *mutex,
236 int timeout_milliseconds)
237 {
238 DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
239 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
240 struct timeval time_now;
241 struct timespec end_time;
242 int result;
243 int old_count;
244
245 _dbus_assert (pmutex->count > 0);
246 _dbus_assert (pthread_equal (pmutex->holder, pthread_self ()));
247
248 gettimeofday (&time_now, NULL);
249
250 end_time.tv_sec = time_now.tv_sec + timeout_milliseconds / 1000;
251 end_time.tv_nsec = (time_now.tv_usec + (timeout_milliseconds % 1000) * 1000) * 1000;
252 if (end_time.tv_nsec > 1000*1000*1000)
253 {
254 end_time.tv_sec += 1;
255 end_time.tv_nsec -= 1000*1000*1000;
256 }
257
258 old_count = pmutex->count;
259 pmutex->count = 0;
260 result = pthread_cond_timedwait (&pcond->cond, &pmutex->lock, &end_time);
261
262 if (result != ETIMEDOUT)
263 {
264 PTHREAD_CHECK ("pthread_cond_timedwait", result);
265 }
266
267 _dbus_assert (pmutex->count == 0);
268 pmutex->count = old_count;
269 pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */
270
271 /* return true if we did not time out */
272 return result != ETIMEDOUT;
273 }
274
275 static void
_dbus_pthread_condvar_wake_one(DBusCondVar * cond)276 _dbus_pthread_condvar_wake_one (DBusCondVar *cond)
277 {
278 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
279
280 PTHREAD_CHECK ("pthread_cond_signal", pthread_cond_signal (&pcond->cond));
281 }
282
283 static void
_dbus_pthread_condvar_wake_all(DBusCondVar * cond)284 _dbus_pthread_condvar_wake_all (DBusCondVar *cond)
285 {
286 DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
287
288 PTHREAD_CHECK ("pthread_cond_broadcast", pthread_cond_broadcast (&pcond->cond));
289 }
290
291 static const DBusThreadFunctions pthread_functions =
292 {
293 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK |
294 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK |
295 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK |
296 DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK |
297 DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK |
298 DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK |
299 DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK |
300 DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK |
301 DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK|
302 DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK,
303 NULL, NULL, NULL, NULL,
304 _dbus_pthread_condvar_new,
305 _dbus_pthread_condvar_free,
306 _dbus_pthread_condvar_wait,
307 _dbus_pthread_condvar_wait_timeout,
308 _dbus_pthread_condvar_wake_one,
309 _dbus_pthread_condvar_wake_all,
310 _dbus_pthread_mutex_new,
311 _dbus_pthread_mutex_free,
312 _dbus_pthread_mutex_lock,
313 _dbus_pthread_mutex_unlock
314 };
315
316 dbus_bool_t
_dbus_threads_init_platform_specific(void)317 _dbus_threads_init_platform_specific (void)
318 {
319 return dbus_threads_init (&pthread_functions);
320 }
321