1 /* Condition variables for multithreading.
2 Copyright (C) 2005-2008 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18 /* Written by Yoann Vandoorselaere <yoann@prelude-ids.org>, 2008.
19 Based on Bruno Haible <bruno@clisp.org> lock.h */
22 Condition variables can be used for waiting until a condition
23 becomes true. In this respect, they are similar to wait queues. But
24 contrary to wait queues, condition variables have different
25 semantics that allows events to be lost when there is no thread
30 Declaration: gl_cond_define(extern, name)
31 Initializer: gl_cond_define_initialized(, name)
32 Initialization: gl_cond_init (name);
33 Waiting: gl_cond_wait (name, lock);
34 Timed wait: bool timedout = gl_cond_timedwait (name, lock, abstime);
35 where lock is a gl_lock_t variable (cf. <glthread/lock.h>)
36 Signaling: gl_cond_signal (name);
37 Broadcasting: gl_cond_broadcast (name);
38 De-initialization: gl_cond_destroy (name);
39 Equivalent functions with control of error handling:
40 Initialization: err = glthread_cond_init (&name);
41 Waiting: err = glthread_cond_wait (&name);
42 Timed wait: err = glthread_cond_timedwait (&name, &lock, abstime);
43 Signaling: err = glthread_cond_signal (&name);
44 Broadcasting: err = glthread_cond_broadcast (&name);
45 De-initialization: err = glthread_cond_destroy (&name);
49 #ifndef _GLTHREAD_COND_H
50 #define _GLTHREAD_COND_H
55 #include "glthread/lock.h"
57 /* ========================================================================= */
61 /* Use the POSIX threads library. */
70 # if PTHREAD_IN_USE_DETECTION_HARD
72 /* The pthread_in_use() detection needs to be done at runtime. */
73 # define pthread_in_use() \
75 extern int glthread_in_use (void);
79 # if USE_POSIX_THREADS_WEAK
81 /* Use weak references to the POSIX threads library. */
83 /* Weak references avoid dragging in external libraries if the other parts
84 of the program don't use them. Here we use them, because we don't want
85 every program that uses libintl to depend on libpthread. This assumes
86 that libpthread would not be loaded after libintl; i.e. if libintl is
87 loaded first, by an executable that does not depend on libpthread, and
88 then a module is dynamically loaded that depends on libpthread, libintl
89 will not be multithread-safe. */
91 /* The way to test at runtime whether libpthread is present is to test
92 whether a function pointer's value, such as &pthread_mutex_init, is
93 non-NULL. However, some versions of GCC have a bug through which, in
94 PIC mode, &foo != NULL always evaluates to true if there is a direct
95 call to foo(...) in the same function. To avoid this, we test the
96 address of a function in libpthread that we don't use. */
98 # pragma weak pthread_cond_init
99 # pragma weak pthread_cond_wait
100 # pragma weak pthread_cond_timedwait
101 # pragma weak pthread_cond_signal
102 # pragma weak pthread_cond_broadcast
103 # pragma weak pthread_cond_destroy
104 # ifndef pthread_self
105 # pragma weak pthread_self
108 # if !PTHREAD_IN_USE_DETECTION_HARD
109 # pragma weak pthread_cancel
110 # define pthread_in_use() (pthread_cancel != NULL)
115 # if !PTHREAD_IN_USE_DETECTION_HARD
116 # define pthread_in_use() 1
121 /* -------------------------- gl_cond_t datatype -------------------------- */
123 typedef pthread_cond_t gl_cond_t;
124 # define gl_cond_define(STORAGECLASS, NAME) \
125 STORAGECLASS pthread_cond_t NAME;
126 # define gl_cond_define_initialized(STORAGECLASS, NAME) \
127 STORAGECLASS pthread_cond_t NAME = gl_cond_initializer;
128 # define gl_cond_initializer \
129 PTHREAD_COND_INITIALIZER
130 # define glthread_cond_init(COND) \
131 (pthread_in_use () ? pthread_cond_init (COND, NULL) : 0)
132 # define glthread_cond_wait(COND, LOCK) \
133 (pthread_in_use () ? pthread_cond_wait (COND, LOCK) : 0)
134 # define glthread_cond_timedwait(COND, LOCK, ABSTIME) \
135 (pthread_in_use () ? pthread_cond_timedwait (COND, LOCK, ABSTIME) : 0)
136 # define glthread_cond_signal(COND) \
137 (pthread_in_use () ? pthread_cond_signal (COND) : 0)
138 # define glthread_cond_broadcast(COND) \
139 (pthread_in_use () ? pthread_cond_broadcast (COND) : 0)
140 # define glthread_cond_destroy(COND) \
141 (pthread_in_use () ? pthread_cond_destroy (COND) : 0)
145 /* ========================================================================= */
149 /* Use the GNU Pth threads library. */
158 # if USE_PTH_THREADS_WEAK
160 /* Use weak references to the GNU Pth threads library. */
162 # pragma weak pth_cond_init
163 # pragma weak pth_cond_await
164 # pragma weak pth_cond_notify
165 # pragma weak pth_event
166 # pragma weak pth_timeout
168 # pragma weak pth_cancel
169 # define pth_in_use() (pth_cancel != NULL)
173 # define pth_in_use() 1
177 /* -------------------------- gl_cond_t datatype -------------------------- */
179 typedef pth_cond_t gl_cond_t;
180 # define gl_cond_define(STORAGECLASS, NAME) \
181 STORAGECLASS pth_cond_t NAME;
182 # define gl_cond_define_initialized(STORAGECLASS, NAME) \
183 STORAGECLASS pth_cond_t NAME = gl_cond_initializer;
184 # define gl_cond_initializer \
186 # define glthread_cond_init(COND) \
187 (pth_in_use () && !pth_cond_init (COND) ? errno : 0)
188 # define glthread_cond_wait(COND, LOCK) \
189 (pth_in_use () && !pth_cond_await (COND, LOCK, NULL) ? errno : 0)
190 # define glthread_cond_timedwait(COND, LOCK, ABSTIME) \
191 (pth_in_use () ? glthread_cond_timedwait_multithreaded (COND, LOCK, ABSTIME) : 0)
192 # define glthread_cond_signal(COND) \
193 (pth_in_use () && !pth_cond_notify (COND, FALSE) ? errno : 0)
194 # define glthread_cond_broadcast(COND) \
195 (pth_in_use () && !pth_cond_notify (COND, TRUE) ? errno : 0)
196 # define glthread_cond_destroy(COND) 0
197 extern int glthread_cond_timedwait_multithreaded (gl_cond_t *cond, gl_lock_t *lock, struct timespec *abstime);
201 /* ========================================================================= */
203 #if USE_SOLARIS_THREADS
205 /* Use the old Solaris threads library. */
215 # if USE_SOLARIS_THREADS_WEAK
217 /* Use weak references to the old Solaris threads library. */
219 # pragma weak cond_init
220 # pragma weak cond_wait
221 # pragma weak cond_timedwait
222 # pragma weak cond_signal
223 # pragma weak cond_broadcast
224 # pragma weak cond_destroy
225 # pragma weak thr_suspend
226 # define thread_in_use() (thr_suspend != NULL)
230 # define thread_in_use() 1
234 /* -------------------------- gl_cond_t datatype -------------------------- */
236 #define ETIMEDOUT ETIME
238 typedef pthread_cond_t gl_cond_t;
239 # define gl_cond_define(STORAGECLASS, NAME) \
240 STORAGECLASS cond_t NAME;
241 # define gl_cond_define_initialized(STORAGECLASS, NAME) \
242 STORAGECLASS cond_t NAME = gl_cond_initializer;
243 # define gl_cond_initializer \
245 # define glthread_cond_init(COND) \
246 (pthread_in_use () ? cond_init (COND, USYNC_THREAD, NULL) : 0)
247 # define glthread_cond_wait(COND, LOCK) \
248 (pthread_in_use () ? cond_wait (COND, LOCK) : 0)
249 # define glthread_cond_timedwait(COND, LOCK, ABSTIME) \
250 (pthread_in_use () ? cond_timedwait (COND, LOCK, ABSTIME) : 0)
251 # define glthread_cond_signal(COND) \
252 (pthread_in_use () ? cond_signal (COND) : 0)
253 # define glthread_cond_broadcast(COND) \
254 (pthread_in_use () ? cond_broadcast (COND) : 0)
255 # define glthread_cond_destroy(COND) \
256 (pthread_in_use () ? cond_destroy (COND) : 0)
260 /* ========================================================================= */
262 #if !(USE_POSIX_THREADS || USE_PTH_THREADS || USE_SOLARIS_THREADS || USE_WIN32_THREADS)
264 /* Provide dummy implementation if threads are not supported. */
266 typedef int gl_cond_t;
267 # define gl_cond_define(STORAGECLASS, NAME)
268 # define gl_cond_define_initialized(STORAGECLASS, NAME)
269 # define glthread_cond_init(COND) 0
270 # define glthread_cond_wait(COND, LOCK) 0
271 # define glthread_cond_timedwait(COND, LOCK, ABSTIME) 0
272 # define glthread_cond_signal(COND) 0
273 # define glthread_cond_broadcast(COND) 0
274 # define glthread_cond_destroy(COND) 0
278 /* ========================================================================= */
280 /* Macros with built-in error handling. */
282 #define gl_cond_init(COND) \
285 if (glthread_cond_init (&COND)) \
289 #define gl_cond_wait(COND, LOCK) \
292 if (glthread_cond_wait (&COND, &LOCK)) \
296 #define gl_cond_timedwait(COND, LOCK, ABSTIME) \
297 gl_cond_timedwait_func (&COND, &LOCK, ABSTIME)
299 gl_cond_timedwait_func (gl_cond_t *cond, gl_lock_t *lock, struct timespec *abstime)
301 int err = glthread_cond_timedwait (cond, lock, abstime);
302 if (err == ETIMEDOUT)
308 #define gl_cond_signal(COND) \
311 if (glthread_cond_signal (&COND)) \
315 #define gl_cond_broadcast(COND) \
318 if (glthread_cond_broadcast (&COND)) \
322 #define gl_cond_destroy(COND) \
325 if (glthread_cond_destroy (&COND)) \
330 #endif /* _GLTHREAD_COND_H */