1 /*****************************************************************************
2 * pthread.c : pthread back-end for LibVLC
3 *****************************************************************************
4 * Copyright (C) 1999-2009 the VideoLAN team
6 * Authors: Jean-Marc Dressler <polux@via.ecp.fr>
7 * Samuel Hocevar <sam@zoy.org>
8 * Gildas Bazin <gbazin@netcourrier.com>
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
25 *****************************************************************************/
31 #include <vlc_common.h>
36 #include <unistd.h> /* fsync() */
41 # include <sys/syscall.h> /* SYS_gettid */
44 #ifdef HAVE_EXECINFO_H
45 # include <execinfo.h>
49 # include <sys/time.h> /* gettimeofday in vlc_cond_timedwait */
53 * Print a backtrace to the standard error for debugging purpose.
55 void vlc_trace (const char *fn, const char *file, unsigned line)
57 fprintf (stderr, "at %s:%u in %s\n", file, line, fn);
58 fflush (stderr); /* needed before switch to low-level I/O */
61 int len = backtrace (stack, sizeof (stack) / sizeof (stack[0]));
62 backtrace_symbols_fd (stack, len, 2);
67 static inline unsigned long vlc_threadid (void)
69 #if defined (__linux__)
70 /* glibc does not provide a call for this */
71 return syscall (SYS_gettid);
74 union { pthread_t th; unsigned long int i; } v = { };
75 v.th = pthread_self ();
82 /*****************************************************************************
83 * vlc_thread_fatal: Report an error from the threading layer
84 *****************************************************************************
85 * This is mostly meant for debugging.
86 *****************************************************************************/
88 vlc_thread_fatal (const char *action, int error,
89 const char *function, const char *file, unsigned line)
91 fprintf (stderr, "LibVLC fatal error %s (%d) in thread %lu ",
92 action, error, vlc_threadid ());
93 vlc_trace (function, file, line);
95 /* Sometimes strerror_r() crashes too, so make sure we print an error
96 * message before we invoke it */
98 /* Avoid the strerror_r() prototype brain damage in glibc */
100 fprintf (stderr, " Error message: %m\n");
105 switch (strerror_r (error, buf, sizeof (buf)))
110 case ERANGE: /* should never happen */
111 msg = "unknwon (too big to display)";
114 msg = "unknown (invalid error number)";
117 fprintf (stderr, " Error message: %s\n", msg);
124 # define VLC_THREAD_ASSERT( action ) \
125 if (val) vlc_thread_fatal (action, val, __func__, __FILE__, __LINE__)
127 # define VLC_THREAD_ASSERT( action ) ((void)val)
130 #if defined (__GLIBC__) && (__GLIBC_MINOR__ < 6)
131 /* This is not prototyped under glibc, though it exists. */
132 int pthread_mutexattr_setkind_np( pthread_mutexattr_t *attr, int kind );
135 /*****************************************************************************
136 * vlc_mutex_init: initialize a mutex
137 *****************************************************************************/
138 int vlc_mutex_init( vlc_mutex_t *p_mutex )
140 pthread_mutexattr_t attr;
143 pthread_mutexattr_init( &attr );
146 /* Create error-checking mutex to detect problems more easily. */
147 # if defined (__GLIBC__) && (__GLIBC_MINOR__ < 6)
148 pthread_mutexattr_setkind_np( &attr, PTHREAD_MUTEX_ERRORCHECK_NP );
150 pthread_mutexattr_settype( &attr, PTHREAD_MUTEX_ERRORCHECK );
153 i_result = pthread_mutex_init( p_mutex, &attr );
154 pthread_mutexattr_destroy( &attr );
158 /*****************************************************************************
159 * vlc_mutex_init: initialize a recursive mutex (Do not use)
160 *****************************************************************************/
161 int vlc_mutex_init_recursive( vlc_mutex_t *p_mutex )
163 pthread_mutexattr_t attr;
166 pthread_mutexattr_init( &attr );
167 #if defined (__GLIBC__) && (__GLIBC_MINOR__ < 6)
168 pthread_mutexattr_setkind_np( &attr, PTHREAD_MUTEX_RECURSIVE_NP );
170 pthread_mutexattr_settype( &attr, PTHREAD_MUTEX_RECURSIVE );
172 i_result = pthread_mutex_init( p_mutex, &attr );
173 pthread_mutexattr_destroy( &attr );
179 * Destroys a mutex. The mutex must not be locked.
181 * @param p_mutex mutex to destroy
182 * @return always succeeds
184 void vlc_mutex_destroy (vlc_mutex_t *p_mutex)
186 int val = pthread_mutex_destroy( p_mutex );
187 VLC_THREAD_ASSERT ("destroying mutex");
191 # ifdef HAVE_VALGRIND_VALGRIND_H
192 # include <valgrind/valgrind.h>
194 # define RUNNING_ON_VALGRIND (0)
197 void vlc_assert_locked (vlc_mutex_t *p_mutex)
199 if (RUNNING_ON_VALGRIND > 0)
201 assert (pthread_mutex_lock (p_mutex) == EDEADLK);
206 * Acquires a mutex. If needed, waits for any other thread to release it.
207 * Beware of deadlocks when locking multiple mutexes at the same time,
208 * or when using mutexes from callbacks.
209 * This function is not a cancellation-point.
211 * @param p_mutex mutex initialized with vlc_mutex_init() or
212 * vlc_mutex_init_recursive()
214 void vlc_mutex_lock (vlc_mutex_t *p_mutex)
216 int val = pthread_mutex_lock( p_mutex );
217 VLC_THREAD_ASSERT ("locking mutex");
221 * Acquires a mutex if and only if it is not currently held by another thread.
222 * This function never sleeps and can be used in delay-critical code paths.
223 * This function is not a cancellation-point.
225 * <b>Beware</b>: If this function fails, then the mutex is held... by another
226 * thread. The calling thread must deal with the error appropriately. That
227 * typically implies postponing the operations that would have required the
228 * mutex. If the thread cannot defer those operations, then it must use
229 * vlc_mutex_lock(). If in doubt, use vlc_mutex_lock() instead.
231 * @param p_mutex mutex initialized with vlc_mutex_init() or
232 * vlc_mutex_init_recursive()
233 * @return 0 if the mutex could be acquired, an error code otherwise.
235 int vlc_mutex_trylock (vlc_mutex_t *p_mutex)
237 int val = pthread_mutex_trylock( p_mutex );
240 VLC_THREAD_ASSERT ("locking mutex");
245 * Releases a mutex (or crashes if the mutex is not locked by the caller).
246 * @param p_mutex mutex locked with vlc_mutex_lock().
248 void vlc_mutex_unlock (vlc_mutex_t *p_mutex)
250 int val = pthread_mutex_unlock( p_mutex );
251 VLC_THREAD_ASSERT ("unlocking mutex");
254 /*****************************************************************************
255 * vlc_cond_init: initialize a condition variable
256 *****************************************************************************/
257 int vlc_cond_init( vlc_cond_t *p_condvar )
259 pthread_condattr_t attr;
262 ret = pthread_condattr_init (&attr);
266 #if !defined (_POSIX_CLOCK_SELECTION)
267 /* Fairly outdated POSIX support (that was defined in 2001) */
268 # define _POSIX_CLOCK_SELECTION (-1)
270 #if (_POSIX_CLOCK_SELECTION >= 0)
271 /* NOTE: This must be the same clock as the one in mtime.c */
272 pthread_condattr_setclock (&attr, CLOCK_MONOTONIC);
275 ret = pthread_cond_init (p_condvar, &attr);
276 pthread_condattr_destroy (&attr);
281 * Destroys a condition variable. No threads shall be waiting or signaling the
283 * @param p_condvar condition variable to destroy
285 void vlc_cond_destroy (vlc_cond_t *p_condvar)
287 int val = pthread_cond_destroy( p_condvar );
288 VLC_THREAD_ASSERT ("destroying condition");
292 * Wakes up one thread waiting on a condition variable, if any.
293 * @param p_condvar condition variable
295 void vlc_cond_signal (vlc_cond_t *p_condvar)
297 int val = pthread_cond_signal( p_condvar );
298 VLC_THREAD_ASSERT ("signaling condition variable");
302 * Wakes up all threads (if any) waiting on a condition variable.
303 * @param p_cond condition variable
305 void vlc_cond_broadcast (vlc_cond_t *p_condvar)
307 pthread_cond_broadcast (p_condvar);
311 * Waits for a condition variable. The calling thread will be suspended until
312 * another thread calls vlc_cond_signal() or vlc_cond_broadcast() on the same
313 * condition variable, the thread is cancelled with vlc_cancel(), or the
314 * system causes a "spurious" unsolicited wake-up.
316 * A mutex is needed to wait on a condition variable. It must <b>not</b> be
317 * a recursive mutex. Although it is possible to use the same mutex for
318 * multiple condition, it is not valid to use different mutexes for the same
319 * condition variable at the same time from different threads.
321 * In case of thread cancellation, the mutex is always locked before
322 * cancellation proceeds.
324 * The canonical way to use a condition variable to wait for event foobar is:
326 vlc_mutex_lock (&lock);
327 mutex_cleanup_push (&lock); // release the mutex in case of cancellation
330 vlc_cond_wait (&wait, &lock);
332 --- foobar is now true, do something about it here --
334 vlc_cleanup_run (); // release the mutex
337 * @param p_condvar condition variable to wait on
338 * @param p_mutex mutex which is unlocked while waiting,
339 * then locked again when waking up.
340 * @param deadline <b>absolute</b> timeout
342 * @return 0 if the condition was signaled, an error code in case of timeout.
344 void vlc_cond_wait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex)
346 int val = pthread_cond_wait( p_condvar, p_mutex );
347 VLC_THREAD_ASSERT ("waiting on condition");
351 * Waits for a condition variable up to a certain date.
352 * This works like vlc_cond_wait(), except for the additional timeout.
354 * @param p_condvar condition variable to wait on
355 * @param p_mutex mutex which is unlocked while waiting,
356 * then locked again when waking up.
357 * @param deadline <b>absolute</b> timeout
359 * @return 0 if the condition was signaled, an error code in case of timeout.
361 int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
365 /* mdate() is mac_absolute_time on OSX, which we must convert to do
366 * the same base than gettimeofday() which pthread_cond_timedwait
368 mtime_t oldbase = mdate();
370 gettimeofday(&tv, NULL);
371 mtime_t newbase = (mtime_t)tv.tv_sec * 1000000 + (mtime_t) tv.tv_usec;
372 deadline = deadline - oldbase + newbase;
374 lldiv_t d = lldiv( deadline, CLOCK_FREQ );
375 struct timespec ts = { d.quot, d.rem * (1000000000 / CLOCK_FREQ) };
377 int val = pthread_cond_timedwait (p_condvar, p_mutex, &ts);
378 if (val != ETIMEDOUT)
379 VLC_THREAD_ASSERT ("timed-waiting on condition");
384 * Allocates a thread-specific variable.
385 * @param key where to store the thread-specific variable handle
386 * @param destr a destruction callback. It is called whenever a thread exits
387 * and the thread-specific variable has a non-NULL value.
388 * @return 0 on success, a system error code otherwise. This function can
389 * actually fail because there is a fixed limit on the number of
390 * thread-specific variable in a process on most systems.
392 int vlc_threadvar_create (vlc_threadvar_t *key, void (*destr) (void *))
394 return pthread_key_create (key, destr);
397 void vlc_threadvar_delete (vlc_threadvar_t *p_tls)
399 pthread_key_delete (*p_tls);
403 * Sets a thread-specific variable.
404 * @param key thread-local variable key (created with vlc_threadvar_create())
405 * @param value new value for the variable for the calling thread
406 * @return 0 on success, a system error code otherwise.
408 int vlc_threadvar_set (vlc_threadvar_t key, void *value)
410 return pthread_setspecific (key, value);
414 * Gets the value of a thread-local variable for the calling thread.
415 * This function cannot fail.
416 * @return the value associated with the given variable for the calling
417 * or NULL if there is no value.
419 void *vlc_threadvar_get (vlc_threadvar_t key)
421 return pthread_getspecific (key);
425 * Creates and starts new thread.
427 * @param p_handle [OUT] pointer to write the handle of the created thread to
428 * @param entry entry point for the thread
429 * @param data data parameter given to the entry point
430 * @param priority thread priority value
431 * @return 0 on success, a standard error code on error.
433 int vlc_clone (vlc_thread_t *p_handle, void * (*entry) (void *), void *data,
439 pthread_attr_init (&attr);
441 /* Block the signals that signals interface plugin handles.
442 * If the LibVLC caller wants to handle some signals by itself, it should
443 * block these before whenever invoking LibVLC. And it must obviously not
444 * start the VLC signals interface plugin.
446 * LibVLC will normally ignore any interruption caused by an asynchronous
447 * signal during a system call. But there may well be some buggy cases
448 * where it fails to handle EINTR (bug reports welcome). Some underlying
449 * libraries might also not handle EINTR properly.
455 sigdelset (&set, SIGHUP);
456 sigaddset (&set, SIGINT);
457 sigaddset (&set, SIGQUIT);
458 sigaddset (&set, SIGTERM);
460 sigaddset (&set, SIGPIPE); /* We don't want this one, really! */
461 pthread_sigmask (SIG_BLOCK, &set, &oldset);
464 #if defined (_POSIX_PRIORITY_SCHEDULING) && (_POSIX_PRIORITY_SCHEDULING >= 0) \
465 && defined (_POSIX_THREAD_PRIORITY_SCHEDULING) \
466 && (_POSIX_THREAD_PRIORITY_SCHEDULING >= 0)
468 struct sched_param sp = { .sched_priority = priority, };
471 if (sp.sched_priority <= 0)
472 sp.sched_priority += sched_get_priority_max (policy = SCHED_OTHER);
474 sp.sched_priority += sched_get_priority_min (policy = SCHED_RR);
476 pthread_attr_setschedpolicy (&attr, policy);
477 pthread_attr_setschedparam (&attr, &sp);
483 /* The thread stack size.
484 * The lower the value, the less address space per thread, the highest
485 * maximum simultaneous threads per process. Too low values will cause
486 * stack overflows and weird crashes. Set with caution. Also keep in mind
487 * that 64-bits platforms consume more stack than 32-bits one.
489 * Thanks to on-demand paging, thread stack size only affects address space
490 * consumption. In terms of memory, threads only use what they need
491 * (rounded up to the page boundary).
493 * For example, on Linux i386, the default is 2 mega-bytes, which supports
494 * about 320 threads per processes. */
495 #define VLC_STACKSIZE (128 * sizeof (void *) * 1024)
498 ret = pthread_attr_setstacksize (&attr, VLC_STACKSIZE);
499 assert (ret == 0); /* fails iif VLC_STACKSIZE is invalid */
502 ret = pthread_create (p_handle, &attr, entry, data);
503 pthread_sigmask (SIG_SETMASK, &oldset, NULL);
504 pthread_attr_destroy (&attr);
509 * Marks a thread as cancelled. Next time the target thread reaches a
510 * cancellation point (while not having disabled cancellation), it will
511 * run its cancellation cleanup handler, the thread variable destructors, and
512 * terminate. vlc_join() must be used afterward regardless of a thread being
515 void vlc_cancel (vlc_thread_t thread_id)
517 pthread_cancel (thread_id);
521 * Waits for a thread to complete (if needed), and destroys it.
522 * This is a cancellation point; in case of cancellation, the join does _not_
525 * @param handle thread handle
526 * @param p_result [OUT] pointer to write the thread return value or NULL
527 * @return 0 on success, a standard error code otherwise.
529 void vlc_join (vlc_thread_t handle, void **result)
531 int val = pthread_join (handle, result);
532 VLC_THREAD_ASSERT ("joining thread");
536 * Save the current cancellation state (enabled or disabled), then disable
537 * cancellation for the calling thread.
538 * This function must be called before entering a piece of code that is not
539 * cancellation-safe, unless it can be proven that the calling thread will not
541 * @return Previous cancellation state (opaque value for vlc_restorecancel()).
543 int vlc_savecancel (void)
546 int val = pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
548 VLC_THREAD_ASSERT ("saving cancellation");
553 * Restore the cancellation state for the calling thread.
554 * @param state previous state as returned by vlc_savecancel().
555 * @return Nothing, always succeeds.
557 void vlc_restorecancel (int state)
562 val = pthread_setcancelstate (state, &oldstate);
563 /* This should fail if an invalid value for given for state */
564 VLC_THREAD_ASSERT ("restoring cancellation");
566 if (oldstate != PTHREAD_CANCEL_DISABLE)
567 vlc_thread_fatal ("restoring cancellation while not disabled", EINVAL,
568 __func__, __FILE__, __LINE__);
570 pthread_setcancelstate (state, NULL);
575 * Issues an explicit deferred cancellation point.
576 * This has no effect if thread cancellation is disabled.
577 * This can be called when there is a rather slow non-sleeping operation.
578 * This is also used to force a cancellation point in a function that would
579 * otherwise "not always" be a one (block_FifoGet() is an example).
581 void vlc_testcancel (void)
583 pthread_testcancel ();
586 void vlc_control_cancel (int cmd, ...)