1 /* Creating and controlling threads.
2 Copyright (C) 2005-2011 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 Bruno Haible <bruno@clisp.org>, 2005.
19 Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
22 /* This file contains primitives for creating and controlling threads.
24 Thread data type: gl_thread_t.
27 thread = gl_thread_create (func, arg);
28 Or with control of error handling:
29 err = glthread_create (&thread, func, arg);
30 extern int glthread_create (gl_thread_t *result,
31 void *(*func) (void *), void *arg);
33 Querying and changing the signal mask of a thread (not supported on all
35 gl_thread_sigmask (how, newmask, oldmask);
36 Or with control of error handling:
37 err = glthread_sigmask (how, newmask, oldmask);
38 extern int glthread_sigmask (int how, const sigset_t *newmask, sigset_t *oldmask);
40 Waiting for termination of another thread:
41 gl_thread_join (thread, &return_value);
42 Or with control of error handling:
43 err = glthread_join (thread, &return_value);
44 extern int glthread_join (gl_thread_t thread, void **return_value_ptr);
46 Getting a reference to the current thread:
47 current = gl_thread_self ();
48 extern gl_thread_t gl_thread_self (void);
50 Terminating the current thread:
51 gl_thread_exit (return_value);
52 extern void gl_thread_exit (void *return_value) __attribute__ ((noreturn));
54 Requesting custom code to be executed at fork() time(not supported on all
56 gl_thread_atfork (prepare_func, parent_func, child_func);
57 Or with control of error handling:
58 err = glthread_atfork (prepare_func, parent_func, child_func);
59 extern int glthread_atfork (void (*prepare_func) (void),
60 void (*parent_func) (void),
61 void (*child_func) (void));
62 Note that even on platforms where this is supported, use of fork() and
63 threads together is problematic, see
64 <http://lists.gnu.org/archive/html/bug-gnulib/2008-08/msg00062.html>
68 #ifndef _GLTHREAD_THREAD_H
69 #define _GLTHREAD_THREAD_H
74 /* ========================================================================= */
78 /* Use the POSIX threads library. */
86 # if PTHREAD_IN_USE_DETECTION_HARD
88 /* The pthread_in_use() detection needs to be done at runtime. */
89 # define pthread_in_use() \
91 extern int glthread_in_use (void);
95 # if USE_POSIX_THREADS_WEAK
97 /* Use weak references to the POSIX threads library. */
99 /* Weak references avoid dragging in external libraries if the other parts
100 of the program don't use them. Here we use them, because we don't want
101 every program that uses libintl to depend on libpthread. This assumes
102 that libpthread would not be loaded after libintl; i.e. if libintl is
103 loaded first, by an executable that does not depend on libpthread, and
104 then a module is dynamically loaded that depends on libpthread, libintl
105 will not be multithread-safe. */
107 /* The way to test at runtime whether libpthread is present is to test
108 whether a function pointer's value, such as &pthread_mutex_init, is
109 non-NULL. However, some versions of GCC have a bug through which, in
110 PIC mode, &foo != NULL always evaluates to true if there is a direct
111 call to foo(...) in the same function. To avoid this, we test the
112 address of a function in libpthread that we don't use. */
114 # pragma weak pthread_create
115 # pragma weak pthread_sigmask
116 # pragma weak pthread_join
117 # ifndef pthread_self
118 # pragma weak pthread_self
120 # pragma weak pthread_exit
121 # if HAVE_PTHREAD_ATFORK
122 # pragma weak pthread_atfork
125 # if !PTHREAD_IN_USE_DETECTION_HARD
126 # pragma weak pthread_cancel
127 # define pthread_in_use() (pthread_cancel != NULL)
132 # if !PTHREAD_IN_USE_DETECTION_HARD
133 # define pthread_in_use() 1
138 /* -------------------------- gl_thread_t datatype -------------------------- */
140 /* This choice of gl_thread_t assumes that
141 pthread_equal (a, b) is equivalent to ((a) == (b)).
142 This is the case on all platforms in use in 2008. */
143 typedef pthread_t gl_thread_t;
144 # define glthread_create(THREADP, FUNC, ARG) \
145 (pthread_in_use () ? pthread_create (THREADP, NULL, FUNC, ARG) : ENOSYS)
146 # define glthread_sigmask(HOW, SET, OSET) \
147 (pthread_in_use () ? pthread_sigmask (HOW, SET, OSET) : 0)
148 # define glthread_join(THREAD, RETVALP) \
149 (pthread_in_use () ? pthread_join (THREAD, RETVALP) : 0)
150 # define gl_thread_self() \
151 (pthread_in_use () ? (void *) pthread_self () : NULL)
152 # define gl_thread_exit(RETVAL) \
153 (pthread_in_use () ? pthread_exit (RETVAL) : 0)
155 # if HAVE_PTHREAD_ATFORK
156 # define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) \
157 (pthread_in_use () ? pthread_atfork (PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) : 0)
159 # define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
168 /* ========================================================================= */
172 /* Use the GNU Pth threads library. */
180 # if USE_PTH_THREADS_WEAK
182 /* Use weak references to the GNU Pth threads library. */
184 # pragma weak pth_spawn
185 # pragma weak pth_sigmask
186 # pragma weak pth_join
187 # pragma weak pth_self
188 # pragma weak pth_exit
190 # pragma weak pth_cancel
191 # define pth_in_use() (pth_cancel != NULL)
195 # define pth_in_use() 1
198 /* -------------------------- gl_thread_t datatype -------------------------- */
200 typedef pth_t gl_thread_t;
201 # define glthread_create(THREADP, FUNC, ARG) \
202 (pth_in_use () ? ((*(THREADP) = pth_spawn (NULL, FUNC, ARG)) ? 0 : errno) : 0)
203 # define glthread_sigmask(HOW, SET, OSET) \
204 (pth_in_use () && !pth_sigmask (HOW, SET, OSET) ? errno : 0)
205 # define glthread_join(THREAD, RETVALP) \
206 (pth_in_use () && !pth_join (THREAD, RETVALP) ? errno : 0)
207 # define gl_thread_self() \
208 (pth_in_use () ? (void *) pth_self () : NULL)
209 # define gl_thread_exit(RETVAL) \
210 (pth_in_use () ? pth_exit (RETVAL) : 0)
211 # define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
219 /* ========================================================================= */
221 #if USE_SOLARIS_THREADS
223 /* Use the old Solaris threads library. */
232 # if USE_SOLARIS_THREADS_WEAK
234 /* Use weak references to the old Solaris threads library. */
236 # pragma weak thr_create
237 # pragma weak thr_join
238 # pragma weak thr_self
239 # pragma weak thr_exit
241 # pragma weak thr_suspend
242 # define thread_in_use() (thr_suspend != NULL)
246 # define thread_in_use() 1
250 /* -------------------------- gl_thread_t datatype -------------------------- */
252 typedef thread_t gl_thread_t;
253 # define glthread_create(THREADP, FUNC, ARG) \
254 (thread_in_use () ? thr_create (NULL, 0, FUNC, ARG, 0, THREADP) : 0)
255 # define glthread_sigmask(HOW, SET, OSET) \
256 (thread_in_use () ? sigprocmask (HOW, SET, OSET) : 0)
257 # define glthread_join(THREAD, RETVALP) \
258 (thread_in_use () ? thr_join (THREAD, NULL, RETVALP) : 0)
259 # define gl_thread_self() \
260 (thread_in_use () ? (void *) thr_self () : NULL)
261 # define gl_thread_exit(RETVAL) \
262 (thread_in_use () ? thr_exit (RETVAL) : 0)
263 # define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
271 /* ========================================================================= */
273 #if USE_WIN32_THREADS
275 # include <windows.h>
281 /* -------------------------- gl_thread_t datatype -------------------------- */
283 /* The gl_thread_t is a pointer to a structure in memory.
284 Why not the thread handle? If it were the thread handle, it would be hard
285 to implement gl_thread_self() (since GetCurrentThread () returns a pseudo-
286 handle, DuplicateHandle (GetCurrentThread ()) returns a handle that must be
287 closed afterwards, and there is no function for quickly retrieving a thread
289 Why not the thread id? I tried it. It did not work: Sometimes ids appeared
290 that did not belong to running threads, and glthread_join failed with ESRCH.
292 typedef struct gl_thread_struct *gl_thread_t;
293 # define glthread_create(THREADP, FUNC, ARG) \
294 glthread_create_func (THREADP, FUNC, ARG)
295 # define glthread_sigmask(HOW, SET, OSET) \
297 # define glthread_join(THREAD, RETVALP) \
298 glthread_join_func (THREAD, RETVALP)
299 # define gl_thread_self() \
300 gl_thread_self_func ()
301 # define gl_thread_exit(RETVAL) \
302 gl_thread_exit_func (RETVAL)
303 # define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
304 extern int glthread_create_func (gl_thread_t *threadp, void * (*func) (void *), void *arg);
305 extern int glthread_join_func (gl_thread_t thread, void **retvalp);
306 extern gl_thread_t gl_thread_self_func (void);
307 extern int gl_thread_exit_func (void *retval);
315 /* ========================================================================= */
317 #if !(USE_POSIX_THREADS || USE_PTH_THREADS || USE_SOLARIS_THREADS || USE_WIN32_THREADS)
319 /* Provide dummy implementation if threads are not supported. */
321 typedef int gl_thread_t;
322 # define glthread_create(THREADP, FUNC, ARG) ENOSYS
323 # define glthread_sigmask(HOW, SET, OSET) 0
324 # define glthread_join(THREAD, RETVALP) 0
325 # define gl_thread_self() 0
326 # define gl_thread_exit(RETVAL) 0
327 # define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
331 /* ========================================================================= */
333 /* Macros with built-in error handling. */
339 static inline gl_thread_t
340 gl_thread_create (void *(*func) (void *arg), void *arg)
345 ret = glthread_create (&thread, func, arg);
350 #define gl_thread_sigmask(HOW, SET, OSET) \
353 if (glthread_sigmask (HOW, SET, OSET)) \
357 #define gl_thread_join(THREAD, RETVAL) \
360 if (glthread_join (THREAD, RETVAL)) \
364 #define gl_thread_atfork(PREPARE, PARENT, CHILD) \
367 if (glthread_atfork (PREPARE, PARENT, CHILD)) \
376 #endif /* _GLTHREAD_THREAD_H */