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 void vlc_mutex_init( vlc_mutex_t *p_mutex )
140 pthread_mutexattr_t attr;
142 if( pthread_mutexattr_init( &attr ) )
145 /* Create error-checking mutex to detect problems more easily. */
146 # if defined (__GLIBC__) && (__GLIBC_MINOR__ < 6)
147 pthread_mutexattr_setkind_np( &attr, PTHREAD_MUTEX_ERRORCHECK_NP );
149 pthread_mutexattr_settype( &attr, PTHREAD_MUTEX_ERRORCHECK );
152 if( pthread_mutex_init( p_mutex, &attr ) )
154 pthread_mutexattr_destroy( &attr );
157 /*****************************************************************************
158 * vlc_mutex_init: initialize a recursive mutex (Do not use)
159 *****************************************************************************/
160 void vlc_mutex_init_recursive( vlc_mutex_t *p_mutex )
162 pthread_mutexattr_t attr;
164 pthread_mutexattr_init( &attr );
165 #if defined (__GLIBC__) && (__GLIBC_MINOR__ < 6)
166 pthread_mutexattr_setkind_np( &attr, PTHREAD_MUTEX_RECURSIVE_NP );
168 pthread_mutexattr_settype( &attr, PTHREAD_MUTEX_RECURSIVE );
170 if( pthread_mutex_init( p_mutex, &attr ) )
172 pthread_mutexattr_destroy( &attr );
177 * Destroys a mutex. The mutex must not be locked.
179 * @param p_mutex mutex to destroy
180 * @return always succeeds
182 void vlc_mutex_destroy (vlc_mutex_t *p_mutex)
184 int val = pthread_mutex_destroy( p_mutex );
185 VLC_THREAD_ASSERT ("destroying mutex");
189 # ifdef HAVE_VALGRIND_VALGRIND_H
190 # include <valgrind/valgrind.h>
192 # define RUNNING_ON_VALGRIND (0)
195 void vlc_assert_locked (vlc_mutex_t *p_mutex)
197 if (RUNNING_ON_VALGRIND > 0)
199 assert (pthread_mutex_lock (p_mutex) == EDEADLK);
204 * Acquires a mutex. If needed, waits for any other thread to release it.
205 * Beware of deadlocks when locking multiple mutexes at the same time,
206 * or when using mutexes from callbacks.
207 * This function is not a cancellation-point.
209 * @param p_mutex mutex initialized with vlc_mutex_init() or
210 * vlc_mutex_init_recursive()
212 void vlc_mutex_lock (vlc_mutex_t *p_mutex)
214 int val = pthread_mutex_lock( p_mutex );
215 VLC_THREAD_ASSERT ("locking mutex");
219 * Acquires a mutex if and only if it is not currently held by another thread.
220 * This function never sleeps and can be used in delay-critical code paths.
221 * This function is not a cancellation-point.
223 * <b>Beware</b>: If this function fails, then the mutex is held... by another
224 * thread. The calling thread must deal with the error appropriately. That
225 * typically implies postponing the operations that would have required the
226 * mutex. If the thread cannot defer those operations, then it must use
227 * vlc_mutex_lock(). If in doubt, use vlc_mutex_lock() instead.
229 * @param p_mutex mutex initialized with vlc_mutex_init() or
230 * vlc_mutex_init_recursive()
231 * @return 0 if the mutex could be acquired, an error code otherwise.
233 int vlc_mutex_trylock (vlc_mutex_t *p_mutex)
235 int val = pthread_mutex_trylock( p_mutex );
238 VLC_THREAD_ASSERT ("locking mutex");
243 * Releases a mutex (or crashes if the mutex is not locked by the caller).
244 * @param p_mutex mutex locked with vlc_mutex_lock().
246 void vlc_mutex_unlock (vlc_mutex_t *p_mutex)
248 int val = pthread_mutex_unlock( p_mutex );
249 VLC_THREAD_ASSERT ("unlocking mutex");
252 /*****************************************************************************
253 * vlc_cond_init: initialize a condition variable
254 *****************************************************************************/
255 void vlc_cond_init( vlc_cond_t *p_condvar )
257 pthread_condattr_t attr;
259 if (pthread_condattr_init (&attr))
261 #if !defined (_POSIX_CLOCK_SELECTION)
262 /* Fairly outdated POSIX support (that was defined in 2001) */
263 # define _POSIX_CLOCK_SELECTION (-1)
265 #if (_POSIX_CLOCK_SELECTION >= 0)
266 /* NOTE: This must be the same clock as the one in mtime.c */
267 pthread_condattr_setclock (&attr, CLOCK_MONOTONIC);
270 if (pthread_cond_init (p_condvar, &attr))
272 pthread_condattr_destroy (&attr);
276 * Destroys a condition variable. No threads shall be waiting or signaling the
278 * @param p_condvar condition variable to destroy
280 void vlc_cond_destroy (vlc_cond_t *p_condvar)
282 int val = pthread_cond_destroy( p_condvar );
283 VLC_THREAD_ASSERT ("destroying condition");
287 * Wakes up one thread waiting on a condition variable, if any.
288 * @param p_condvar condition variable
290 void vlc_cond_signal (vlc_cond_t *p_condvar)
292 int val = pthread_cond_signal( p_condvar );
293 VLC_THREAD_ASSERT ("signaling condition variable");
297 * Wakes up all threads (if any) waiting on a condition variable.
298 * @param p_cond condition variable
300 void vlc_cond_broadcast (vlc_cond_t *p_condvar)
302 pthread_cond_broadcast (p_condvar);
306 * Waits for a condition variable. The calling thread will be suspended until
307 * another thread calls vlc_cond_signal() or vlc_cond_broadcast() on the same
308 * condition variable, the thread is cancelled with vlc_cancel(), or the
309 * system causes a "spurious" unsolicited wake-up.
311 * A mutex is needed to wait on a condition variable. It must <b>not</b> be
312 * a recursive mutex. Although it is possible to use the same mutex for
313 * multiple condition, it is not valid to use different mutexes for the same
314 * condition variable at the same time from different threads.
316 * In case of thread cancellation, the mutex is always locked before
317 * cancellation proceeds.
319 * The canonical way to use a condition variable to wait for event foobar is:
321 vlc_mutex_lock (&lock);
322 mutex_cleanup_push (&lock); // release the mutex in case of cancellation
325 vlc_cond_wait (&wait, &lock);
327 --- foobar is now true, do something about it here --
329 vlc_cleanup_run (); // release the mutex
332 * @param p_condvar condition variable to wait on
333 * @param p_mutex mutex which is unlocked while waiting,
334 * then locked again when waking up.
335 * @param deadline <b>absolute</b> timeout
337 * @return 0 if the condition was signaled, an error code in case of timeout.
339 void vlc_cond_wait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex)
341 int val = pthread_cond_wait( p_condvar, p_mutex );
342 VLC_THREAD_ASSERT ("waiting on condition");
346 * Waits for a condition variable up to a certain date.
347 * This works like vlc_cond_wait(), except for the additional timeout.
349 * @param p_condvar condition variable to wait on
350 * @param p_mutex mutex which is unlocked while waiting,
351 * then locked again when waking up.
352 * @param deadline <b>absolute</b> timeout
354 * @return 0 if the condition was signaled, an error code in case of timeout.
356 int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
359 #if defined(__APPLE__) && !defined(__powerpc__) && !defined( __ppc__ ) && !defined( __ppc64__ )
360 /* mdate() is mac_absolute_time on OSX, which we must convert to do
361 * the same base than gettimeofday() which pthread_cond_timedwait
363 mtime_t oldbase = mdate();
365 gettimeofday(&tv, NULL);
366 mtime_t newbase = (mtime_t)tv.tv_sec * 1000000 + (mtime_t) tv.tv_usec;
367 deadline = deadline - oldbase + newbase;
369 lldiv_t d = lldiv( deadline, CLOCK_FREQ );
370 struct timespec ts = { d.quot, d.rem * (1000000000 / CLOCK_FREQ) };
372 int val = pthread_cond_timedwait (p_condvar, p_mutex, &ts);
373 if (val != ETIMEDOUT)
374 VLC_THREAD_ASSERT ("timed-waiting on condition");
379 * Initializes a read/write lock.
381 void vlc_rwlock_init (vlc_rwlock_t *lock)
383 if (pthread_rwlock_init (lock, NULL))
388 * Destroys an initialized unused read/write lock.
390 void vlc_rwlock_destroy (vlc_rwlock_t *lock)
392 int val = pthread_rwlock_destroy (lock);
393 VLC_THREAD_ASSERT ("destroying R/W lock");
397 * Acquires a read/write lock for reading. Recursion is allowed.
399 void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
401 int val = pthread_rwlock_rdlock (lock);
402 VLC_THREAD_ASSERT ("acquiring R/W lock for reading");
406 * Acquires a read/write lock for writing. Recursion is not allowed.
408 void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
410 int val = pthread_rwlock_wrlock (lock);
411 VLC_THREAD_ASSERT ("acquiring R/W lock for writing");
415 * Releases a read/write lock.
417 void vlc_rwlock_unlock (vlc_rwlock_t *lock)
419 int val = pthread_rwlock_unlock (lock);
420 VLC_THREAD_ASSERT ("releasing R/W lock");
424 * Allocates a thread-specific variable.
425 * @param key where to store the thread-specific variable handle
426 * @param destr a destruction callback. It is called whenever a thread exits
427 * and the thread-specific variable has a non-NULL value.
428 * @return 0 on success, a system error code otherwise. This function can
429 * actually fail because there is a fixed limit on the number of
430 * thread-specific variable in a process on most systems.
432 int vlc_threadvar_create (vlc_threadvar_t *key, void (*destr) (void *))
434 return pthread_key_create (key, destr);
437 void vlc_threadvar_delete (vlc_threadvar_t *p_tls)
439 pthread_key_delete (*p_tls);
443 * Sets a thread-specific variable.
444 * @param key thread-local variable key (created with vlc_threadvar_create())
445 * @param value new value for the variable for the calling thread
446 * @return 0 on success, a system error code otherwise.
448 int vlc_threadvar_set (vlc_threadvar_t key, void *value)
450 return pthread_setspecific (key, value);
454 * Gets the value of a thread-local variable for the calling thread.
455 * This function cannot fail.
456 * @return the value associated with the given variable for the calling
457 * or NULL if there is no value.
459 void *vlc_threadvar_get (vlc_threadvar_t key)
461 return pthread_getspecific (key);
464 static bool rt_priorities = false;
465 static int rt_offset;
467 void vlc_threads_setup (libvlc_int_t *p_libvlc)
469 static vlc_mutex_t lock = VLC_STATIC_MUTEX;
470 static bool initialized = false;
472 vlc_mutex_lock (&lock);
473 /* Initializes real-time priorities before any thread is created,
474 * just once per process. */
478 if (config_GetInt (p_libvlc, "rt-priority"))
481 rt_offset = config_GetInt (p_libvlc, "rt-offset");
482 rt_priorities = true;
486 vlc_mutex_unlock (&lock);
490 * Creates and starts new thread.
492 * @param p_handle [OUT] pointer to write the handle of the created thread to
493 * @param entry entry point for the thread
494 * @param data data parameter given to the entry point
495 * @param priority thread priority value
496 * @return 0 on success, a standard error code on error.
498 int vlc_clone (vlc_thread_t *p_handle, void * (*entry) (void *), void *data,
504 pthread_attr_init (&attr);
506 /* Block the signals that signals interface plugin handles.
507 * If the LibVLC caller wants to handle some signals by itself, it should
508 * block these before whenever invoking LibVLC. And it must obviously not
509 * start the VLC signals interface plugin.
511 * LibVLC will normally ignore any interruption caused by an asynchronous
512 * signal during a system call. But there may well be some buggy cases
513 * where it fails to handle EINTR (bug reports welcome). Some underlying
514 * libraries might also not handle EINTR properly.
520 sigdelset (&set, SIGHUP);
521 sigaddset (&set, SIGINT);
522 sigaddset (&set, SIGQUIT);
523 sigaddset (&set, SIGTERM);
525 sigaddset (&set, SIGPIPE); /* We don't want this one, really! */
526 pthread_sigmask (SIG_BLOCK, &set, &oldset);
529 #if defined (_POSIX_PRIORITY_SCHEDULING) && (_POSIX_PRIORITY_SCHEDULING >= 0) \
530 && defined (_POSIX_THREAD_PRIORITY_SCHEDULING) \
531 && (_POSIX_THREAD_PRIORITY_SCHEDULING >= 0)
534 struct sched_param sp = { .sched_priority = priority + rt_offset, };
537 if (sp.sched_priority <= 0)
538 sp.sched_priority += sched_get_priority_max (policy = SCHED_OTHER);
540 sp.sched_priority += sched_get_priority_min (policy = SCHED_RR);
542 pthread_attr_setschedpolicy (&attr, policy);
543 pthread_attr_setschedparam (&attr, &sp);
549 /* The thread stack size.
550 * The lower the value, the less address space per thread, the highest
551 * maximum simultaneous threads per process. Too low values will cause
552 * stack overflows and weird crashes. Set with caution. Also keep in mind
553 * that 64-bits platforms consume more stack than 32-bits one.
555 * Thanks to on-demand paging, thread stack size only affects address space
556 * consumption. In terms of memory, threads only use what they need
557 * (rounded up to the page boundary).
559 * For example, on Linux i386, the default is 2 mega-bytes, which supports
560 * about 320 threads per processes. */
561 #define VLC_STACKSIZE (128 * sizeof (void *) * 1024)
564 ret = pthread_attr_setstacksize (&attr, VLC_STACKSIZE);
565 assert (ret == 0); /* fails iif VLC_STACKSIZE is invalid */
568 ret = pthread_create (p_handle, &attr, entry, data);
569 pthread_sigmask (SIG_SETMASK, &oldset, NULL);
570 pthread_attr_destroy (&attr);
575 * Marks a thread as cancelled. Next time the target thread reaches a
576 * cancellation point (while not having disabled cancellation), it will
577 * run its cancellation cleanup handler, the thread variable destructors, and
578 * terminate. vlc_join() must be used afterward regardless of a thread being
581 void vlc_cancel (vlc_thread_t thread_id)
583 pthread_cancel (thread_id);
587 * Waits for a thread to complete (if needed), then destroys it.
588 * This is a cancellation point; in case of cancellation, the join does _not_
591 * A thread cannot join itself (normally VLC will abort if this is attempted).
592 * Also, a detached thread <b>cannot</b> be joined.
594 * @param handle thread handle
595 * @param p_result [OUT] pointer to write the thread return value or NULL
597 void vlc_join (vlc_thread_t handle, void **result)
599 int val = pthread_join (handle, result);
600 VLC_THREAD_ASSERT ("joining thread");
604 * Detaches a thread. When the specified thread completes, it will be
605 * automatically destroyed (in particular, its stack will be reclaimed),
606 * instead of waiting for another thread to call vlc_join(). If the thread has
607 * already completed, it will be destroyed immediately.
609 * When a thread performs some work asynchronously and may complete much
610 * earlier than it can be joined, detaching the thread can save memory.
611 * However, care must be taken that any resources used by a detached thread
612 * remains valid until the thread completes. This will typically involve some
613 * kind of thread-safe signaling.
615 * A thread may detach itself.
617 * @param handle thread handle
619 void vlc_detach (vlc_thread_t handle)
621 int val = pthread_detach (handle);
622 VLC_THREAD_ASSERT ("detaching thread");
626 * Save the current cancellation state (enabled or disabled), then disable
627 * cancellation for the calling thread.
628 * This function must be called before entering a piece of code that is not
629 * cancellation-safe, unless it can be proven that the calling thread will not
631 * @return Previous cancellation state (opaque value for vlc_restorecancel()).
633 int vlc_savecancel (void)
636 int val = pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
638 VLC_THREAD_ASSERT ("saving cancellation");
643 * Restore the cancellation state for the calling thread.
644 * @param state previous state as returned by vlc_savecancel().
645 * @return Nothing, always succeeds.
647 void vlc_restorecancel (int state)
652 val = pthread_setcancelstate (state, &oldstate);
653 /* This should fail if an invalid value for given for state */
654 VLC_THREAD_ASSERT ("restoring cancellation");
656 if (oldstate != PTHREAD_CANCEL_DISABLE)
657 vlc_thread_fatal ("restoring cancellation while not disabled", EINVAL,
658 __func__, __FILE__, __LINE__);
660 pthread_setcancelstate (state, NULL);
665 * Issues an explicit deferred cancellation point.
666 * This has no effect if thread cancellation is disabled.
667 * This can be called when there is a rather slow non-sleeping operation.
668 * This is also used to force a cancellation point in a function that would
669 * otherwise "not always" be a one (block_FifoGet() is an example).
671 void vlc_testcancel (void)
673 pthread_testcancel ();
676 void vlc_control_cancel (int cmd, ...)
688 void (*func) (void *);
690 mtime_t value, interval;
695 static void *vlc_timer_do (void *data)
697 struct vlc_timer *timer = data;
699 timer->func (timer->data);
701 vlc_mutex_lock (&timer->lock);
702 assert (timer->users > 0);
703 if (--timer->users == 0)
704 vlc_cond_signal (&timer->wait);
705 vlc_mutex_unlock (&timer->lock);
709 static void *vlc_timer_thread (void *data)
711 struct vlc_timer *timer = data;
712 mtime_t value, interval;
714 vlc_mutex_lock (&timer->lock);
715 value = timer->value;
716 interval = timer->interval;
717 vlc_mutex_unlock (&timer->lock);
725 vlc_mutex_lock (&timer->lock);
726 if (vlc_clone (&th, vlc_timer_do, timer, VLC_THREAD_PRIORITY_INPUT))
733 vlc_mutex_unlock (&timer->lock);
743 * Initializes an asynchronous timer.
744 * @warning Asynchronous timers are processed from an unspecified thread.
745 * Also, multiple occurences of an interval timer can run concurrently.
747 * @param id pointer to timer to be initialized
748 * @param func function that the timer will call
749 * @param data parameter for the timer function
750 * @return 0 on success, a system error code otherwise.
752 int vlc_timer_create (vlc_timer_t *id, void (*func) (void *), void *data)
754 struct vlc_timer *timer = malloc (sizeof (*timer));
758 vlc_mutex_init (&timer->lock);
759 vlc_cond_init (&timer->wait);
772 * Destroys an initialized timer. If needed, the timer is first disarmed.
773 * This function is undefined if the specified timer is not initialized.
775 * @warning This function <b>must</b> be called before the timer data can be
776 * freed and before the timer callback function can be unloaded.
778 * @param timer timer to destroy
780 void vlc_timer_destroy (vlc_timer_t timer)
782 vlc_timer_schedule (timer, false, 0, 0);
783 vlc_mutex_lock (&timer->lock);
784 while (timer->users != 0)
785 vlc_cond_wait (&timer->wait, &timer->lock);
786 vlc_mutex_unlock (&timer->lock);
788 vlc_cond_destroy (&timer->wait);
789 vlc_mutex_destroy (&timer->lock);
794 * Arm or disarm an initialized timer.
795 * This functions overrides any previous call to itself.
797 * @note A timer can fire later than requested due to system scheduling
798 * limitations. An interval timer can fail to trigger sometimes, either because
799 * the system is busy or suspended, or because a previous iteration of the
800 * timer is still running. See also vlc_timer_getoverrun().
802 * @param timer initialized timer
803 * @param absolute the timer value origin is the same as mdate() if true,
804 * the timer value is relative to now if false.
805 * @param value zero to disarm the timer, otherwise the initial time to wait
806 * before firing the timer.
807 * @param interval zero to fire the timer just once, otherwise the timer
808 * repetition interval.
810 void vlc_timer_schedule (vlc_timer_t timer, bool absolute,
811 mtime_t value, mtime_t interval)
813 vlc_mutex_lock (&timer->lock);
816 vlc_cancel (timer->thread);
817 vlc_join (timer->thread, NULL);
821 && (vlc_clone (&timer->thread, vlc_timer_thread, timer,
822 VLC_THREAD_PRIORITY_INPUT) == 0))
824 timer->value = (absolute ? 0 : mdate ()) + value;
825 timer->interval = interval;
827 vlc_mutex_unlock (&timer->lock);
831 * Fetch and reset the overrun counter for a timer.
832 * @param timer initialized timer
833 * @return the timer overrun counter, i.e. the number of times that the timer
834 * should have run but did not since the last actual run. If all is well, this
837 unsigned vlc_timer_getoverrun (vlc_timer_t timer)
841 vlc_mutex_lock (&timer->lock);
842 ret = timer->overruns;
844 vlc_mutex_unlock (&timer->lock);