1 /*****************************************************************************
2 * thread.c : pthread back-end for LibVLC
3 *****************************************************************************
4 * Copyright (C) 1999-2009 VLC authors and VideoLAN
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 it
13 * under the terms of the GNU Lesser General Public License as published by
14 * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
22 * You should have received a copy of the GNU Lesser General Public License
23 * along with this program; if not, write to the Free Software Foundation,
24 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
25 *****************************************************************************/
31 #include <vlc_common.h>
32 #include <vlc_atomic.h>
41 #include <sys/types.h>
42 #include <unistd.h> /* fsync() */
47 # include <sys/syscall.h> /* SYS_gettid */
49 #ifdef HAVE_EXECINFO_H
50 # include <execinfo.h>
53 # include <sys/processor.h>
54 # include <sys/pset.h>
57 #if !defined (_POSIX_TIMERS)
58 # define _POSIX_TIMERS (-1)
60 #if !defined (_POSIX_CLOCK_SELECTION)
61 /* Clock selection was defined in 2001 and became mandatory in 2008. */
62 # define _POSIX_CLOCK_SELECTION (-1)
64 #if !defined (_POSIX_MONOTONIC_CLOCK)
65 # define _POSIX_MONOTONIC_CLOCK (-1)
68 #if (_POSIX_TIMERS > 0)
69 static unsigned vlc_clock_prec;
71 # if (_POSIX_MONOTONIC_CLOCK > 0) && (_POSIX_CLOCK_SELECTION > 0)
72 /* Compile-time POSIX monotonic clock support */
73 # define vlc_clock_id (CLOCK_MONOTONIC)
75 # elif (_POSIX_MONOTONIC_CLOCK == 0) && (_POSIX_CLOCK_SELECTION > 0)
76 /* Run-time POSIX monotonic clock support (see clock_setup() below) */
77 static clockid_t vlc_clock_id;
80 /* No POSIX monotonic clock support */
81 # define vlc_clock_id (CLOCK_REALTIME)
82 # warning Monotonic clock not available. Expect timing issues.
84 # endif /* _POSIX_MONOTONIC_CLOKC */
86 static void vlc_clock_setup_once (void)
88 # if (_POSIX_MONOTONIC_CLOCK == 0)
89 long val = sysconf (_SC_MONOTONIC_CLOCK);
91 vlc_clock_id = (val < 0) ? CLOCK_REALTIME : CLOCK_MONOTONIC;
95 if (unlikely(clock_getres (vlc_clock_id, &res) != 0 || res.tv_sec != 0))
97 vlc_clock_prec = (res.tv_nsec + 500) / 1000;
100 static pthread_once_t vlc_clock_once = PTHREAD_ONCE_INIT;
102 # define vlc_clock_setup() \
103 pthread_once(&vlc_clock_once, vlc_clock_setup_once)
105 #else /* _POSIX_TIMERS */
107 # include <sys/time.h> /* gettimeofday() */
108 # if defined (HAVE_DECL_NANOSLEEP) && !HAVE_DECL_NANOSLEEP
109 int nanosleep (struct timespec *, struct timespec *);
112 # define vlc_clock_setup() (void)0
113 # warning Monotonic clock not available. Expect timing issues.
114 #endif /* _POSIX_TIMERS */
116 static struct timespec mtime_to_ts (mtime_t date)
118 lldiv_t d = lldiv (date, CLOCK_FREQ);
119 struct timespec ts = { d.quot, d.rem * (1000000000 / CLOCK_FREQ) };
125 * Print a backtrace to the standard error for debugging purpose.
127 void vlc_trace (const char *fn, const char *file, unsigned line)
129 fprintf (stderr, "at %s:%u in %s\n", file, line, fn);
130 fflush (stderr); /* needed before switch to low-level I/O */
131 #ifdef HAVE_BACKTRACE
133 int len = backtrace (stack, sizeof (stack) / sizeof (stack[0]));
134 backtrace_symbols_fd (stack, len, 2);
139 static inline unsigned long vlc_threadid (void)
141 #if defined (__linux__)
142 /* glibc does not provide a call for this */
143 return syscall (__NR_gettid);
146 union { pthread_t th; unsigned long int i; } v = { };
147 v.th = pthread_self ();
155 * Reports a fatal error from the threading layer, for debugging purposes.
158 vlc_thread_fatal (const char *action, int error,
159 const char *function, const char *file, unsigned line)
161 int canc = vlc_savecancel ();
162 fprintf (stderr, "LibVLC fatal error %s (%d) in thread %lu ",
163 action, error, vlc_threadid ());
164 vlc_trace (function, file, line);
165 perror ("Thread error");
168 vlc_restorecancel (canc);
172 # define VLC_THREAD_ASSERT( action ) \
174 vlc_thread_fatal (action, val, __func__, __FILE__, __LINE__)
176 # define VLC_THREAD_ASSERT( action ) ((void)val)
180 * Initializes a fast mutex.
182 void vlc_mutex_init( vlc_mutex_t *p_mutex )
184 pthread_mutexattr_t attr;
186 if (unlikely(pthread_mutexattr_init (&attr)))
189 pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_DEFAULT);
191 pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK);
193 if (unlikely(pthread_mutex_init (p_mutex, &attr)))
195 pthread_mutexattr_destroy( &attr );
199 * Initializes a recursive mutex.
200 * \warning This is strongly discouraged. Please use normal mutexes.
202 void vlc_mutex_init_recursive( vlc_mutex_t *p_mutex )
204 pthread_mutexattr_t attr;
206 if (unlikely(pthread_mutexattr_init (&attr)))
208 pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
209 if (unlikely(pthread_mutex_init (p_mutex, &attr)))
211 pthread_mutexattr_destroy( &attr );
216 * Destroys a mutex. The mutex must not be locked.
218 * @param p_mutex mutex to destroy
219 * @return always succeeds
221 void vlc_mutex_destroy (vlc_mutex_t *p_mutex)
223 int val = pthread_mutex_destroy( p_mutex );
224 VLC_THREAD_ASSERT ("destroying mutex");
228 # ifdef HAVE_VALGRIND_VALGRIND_H
229 # include <valgrind/valgrind.h>
231 # define RUNNING_ON_VALGRIND (0)
235 * Asserts that a mutex is locked by the calling thread.
237 void vlc_assert_locked (vlc_mutex_t *p_mutex)
239 if (RUNNING_ON_VALGRIND > 0)
241 assert (pthread_mutex_lock (p_mutex) == EDEADLK);
246 * Acquires a mutex. If needed, waits for any other thread to release it.
247 * Beware of deadlocks when locking multiple mutexes at the same time,
248 * or when using mutexes from callbacks.
249 * This function is not a cancellation-point.
251 * @param p_mutex mutex initialized with vlc_mutex_init() or
252 * vlc_mutex_init_recursive()
254 void vlc_mutex_lock (vlc_mutex_t *p_mutex)
256 int val = pthread_mutex_lock( p_mutex );
257 VLC_THREAD_ASSERT ("locking mutex");
261 * Acquires a mutex if and only if it is not currently held by another thread.
262 * This function never sleeps and can be used in delay-critical code paths.
263 * This function is not a cancellation-point.
265 * <b>Beware</b>: If this function fails, then the mutex is held... by another
266 * thread. The calling thread must deal with the error appropriately. That
267 * typically implies postponing the operations that would have required the
268 * mutex. If the thread cannot defer those operations, then it must use
269 * vlc_mutex_lock(). If in doubt, use vlc_mutex_lock() instead.
271 * @param p_mutex mutex initialized with vlc_mutex_init() or
272 * vlc_mutex_init_recursive()
273 * @return 0 if the mutex could be acquired, an error code otherwise.
275 int vlc_mutex_trylock (vlc_mutex_t *p_mutex)
277 int val = pthread_mutex_trylock( p_mutex );
280 VLC_THREAD_ASSERT ("locking mutex");
285 * Releases a mutex (or crashes if the mutex is not locked by the caller).
286 * @param p_mutex mutex locked with vlc_mutex_lock().
288 void vlc_mutex_unlock (vlc_mutex_t *p_mutex)
290 int val = pthread_mutex_unlock( p_mutex );
291 VLC_THREAD_ASSERT ("unlocking mutex");
295 * Initializes a condition variable.
297 void vlc_cond_init (vlc_cond_t *p_condvar)
299 pthread_condattr_t attr;
301 if (unlikely(pthread_condattr_init (&attr)))
303 #if (_POSIX_CLOCK_SELECTION > 0)
305 pthread_condattr_setclock (&attr, vlc_clock_id);
307 if (unlikely(pthread_cond_init (p_condvar, &attr)))
309 pthread_condattr_destroy (&attr);
313 * Initializes a condition variable.
314 * Contrary to vlc_cond_init(), the wall clock will be used as a reference for
315 * the vlc_cond_timedwait() time-out parameter.
317 void vlc_cond_init_daytime (vlc_cond_t *p_condvar)
319 if (unlikely(pthread_cond_init (p_condvar, NULL)))
324 * Destroys a condition variable. No threads shall be waiting or signaling the
326 * @param p_condvar condition variable to destroy
328 void vlc_cond_destroy (vlc_cond_t *p_condvar)
330 int val = pthread_cond_destroy( p_condvar );
331 VLC_THREAD_ASSERT ("destroying condition");
335 * Wakes up one thread waiting on a condition variable, if any.
336 * @param p_condvar condition variable
338 void vlc_cond_signal (vlc_cond_t *p_condvar)
340 int val = pthread_cond_signal( p_condvar );
341 VLC_THREAD_ASSERT ("signaling condition variable");
345 * Wakes up all threads (if any) waiting on a condition variable.
346 * @param p_cond condition variable
348 void vlc_cond_broadcast (vlc_cond_t *p_condvar)
350 pthread_cond_broadcast (p_condvar);
354 * Waits for a condition variable. The calling thread will be suspended until
355 * another thread calls vlc_cond_signal() or vlc_cond_broadcast() on the same
356 * condition variable, the thread is cancelled with vlc_cancel(), or the
357 * system causes a "spurious" unsolicited wake-up.
359 * A mutex is needed to wait on a condition variable. It must <b>not</b> be
360 * a recursive mutex. Although it is possible to use the same mutex for
361 * multiple condition, it is not valid to use different mutexes for the same
362 * condition variable at the same time from different threads.
364 * In case of thread cancellation, the mutex is always locked before
365 * cancellation proceeds.
367 * The canonical way to use a condition variable to wait for event foobar is:
369 vlc_mutex_lock (&lock);
370 mutex_cleanup_push (&lock); // release the mutex in case of cancellation
373 vlc_cond_wait (&wait, &lock);
375 --- foobar is now true, do something about it here --
377 vlc_cleanup_run (); // release the mutex
380 * @param p_condvar condition variable to wait on
381 * @param p_mutex mutex which is unlocked while waiting,
382 * then locked again when waking up.
383 * @param deadline <b>absolute</b> timeout
385 void vlc_cond_wait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex)
387 int val = pthread_cond_wait( p_condvar, p_mutex );
388 VLC_THREAD_ASSERT ("waiting on condition");
392 * Waits for a condition variable up to a certain date.
393 * This works like vlc_cond_wait(), except for the additional time-out.
395 * If the variable was initialized with vlc_cond_init(), the timeout has the
396 * same arbitrary origin as mdate(). If the variable was initialized with
397 * vlc_cond_init_daytime(), the timeout is expressed from the Unix epoch.
399 * @param p_condvar condition variable to wait on
400 * @param p_mutex mutex which is unlocked while waiting,
401 * then locked again when waking up.
402 * @param deadline <b>absolute</b> timeout
404 * @return 0 if the condition was signaled, an error code in case of timeout.
406 int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
409 struct timespec ts = mtime_to_ts (deadline);
410 int val = pthread_cond_timedwait (p_condvar, p_mutex, &ts);
411 if (val != ETIMEDOUT)
412 VLC_THREAD_ASSERT ("timed-waiting on condition");
417 * Initializes a semaphore.
419 void vlc_sem_init (vlc_sem_t *sem, unsigned value)
421 if (unlikely(sem_init (sem, 0, value)))
426 * Destroys a semaphore.
428 void vlc_sem_destroy (vlc_sem_t *sem)
432 if (likely(sem_destroy (sem) == 0))
437 VLC_THREAD_ASSERT ("destroying semaphore");
441 * Increments the value of a semaphore.
442 * @return 0 on success, EOVERFLOW in case of integer overflow
444 int vlc_sem_post (vlc_sem_t *sem)
448 if (likely(sem_post (sem) == 0))
453 if (unlikely(val != EOVERFLOW))
454 VLC_THREAD_ASSERT ("unlocking semaphore");
459 * Atomically wait for the semaphore to become non-zero (if needed),
460 * then decrements it.
462 void vlc_sem_wait (vlc_sem_t *sem)
467 if (likely(sem_wait (sem) == 0))
469 while ((val = errno) == EINTR);
471 VLC_THREAD_ASSERT ("locking semaphore");
475 * Initializes a read/write lock.
477 void vlc_rwlock_init (vlc_rwlock_t *lock)
479 if (unlikely(pthread_rwlock_init (lock, NULL)))
484 * Destroys an initialized unused read/write lock.
486 void vlc_rwlock_destroy (vlc_rwlock_t *lock)
488 int val = pthread_rwlock_destroy (lock);
489 VLC_THREAD_ASSERT ("destroying R/W lock");
493 * Acquires a read/write lock for reading. Recursion is allowed.
494 * @note This function may be a point of cancellation.
496 void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
498 int val = pthread_rwlock_rdlock (lock);
499 VLC_THREAD_ASSERT ("acquiring R/W lock for reading");
503 * Acquires a read/write lock for writing. Recursion is not allowed.
504 * @note This function may be a point of cancellation.
506 void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
508 int val = pthread_rwlock_wrlock (lock);
509 VLC_THREAD_ASSERT ("acquiring R/W lock for writing");
513 * Releases a read/write lock.
515 void vlc_rwlock_unlock (vlc_rwlock_t *lock)
517 int val = pthread_rwlock_unlock (lock);
518 VLC_THREAD_ASSERT ("releasing R/W lock");
522 * Allocates a thread-specific variable.
523 * @param key where to store the thread-specific variable handle
524 * @param destr a destruction callback. It is called whenever a thread exits
525 * and the thread-specific variable has a non-NULL value.
526 * @return 0 on success, a system error code otherwise. This function can
527 * actually fail because there is a fixed limit on the number of
528 * thread-specific variable in a process on most systems.
530 int vlc_threadvar_create (vlc_threadvar_t *key, void (*destr) (void *))
532 return pthread_key_create (key, destr);
535 void vlc_threadvar_delete (vlc_threadvar_t *p_tls)
537 pthread_key_delete (*p_tls);
541 * Sets a thread-specific variable.
542 * @param key thread-local variable key (created with vlc_threadvar_create())
543 * @param value new value for the variable for the calling thread
544 * @return 0 on success, a system error code otherwise.
546 int vlc_threadvar_set (vlc_threadvar_t key, void *value)
548 return pthread_setspecific (key, value);
552 * Gets the value of a thread-local variable for the calling thread.
553 * This function cannot fail.
554 * @return the value associated with the given variable for the calling
555 * or NULL if there is no value.
557 void *vlc_threadvar_get (vlc_threadvar_t key)
559 return pthread_getspecific (key);
562 static bool rt_priorities = false;
563 static int rt_offset;
565 void vlc_threads_setup (libvlc_int_t *p_libvlc)
567 static vlc_mutex_t lock = VLC_STATIC_MUTEX;
568 static bool initialized = false;
570 vlc_mutex_lock (&lock);
571 /* Initializes real-time priorities before any thread is created,
572 * just once per process. */
575 if (var_InheritBool (p_libvlc, "rt-priority"))
577 rt_offset = var_InheritInteger (p_libvlc, "rt-offset");
578 rt_priorities = true;
582 vlc_mutex_unlock (&lock);
586 static int vlc_clone_attr (vlc_thread_t *th, pthread_attr_t *attr,
587 void *(*entry) (void *), void *data, int priority)
591 /* Block the signals that signals interface plugin handles.
592 * If the LibVLC caller wants to handle some signals by itself, it should
593 * block these before whenever invoking LibVLC. And it must obviously not
594 * start the VLC signals interface plugin.
596 * LibVLC will normally ignore any interruption caused by an asynchronous
597 * signal during a system call. But there may well be some buggy cases
598 * where it fails to handle EINTR (bug reports welcome). Some underlying
599 * libraries might also not handle EINTR properly.
605 sigdelset (&set, SIGHUP);
606 sigaddset (&set, SIGINT);
607 sigaddset (&set, SIGQUIT);
608 sigaddset (&set, SIGTERM);
610 sigaddset (&set, SIGPIPE); /* We don't want this one, really! */
611 pthread_sigmask (SIG_BLOCK, &set, &oldset);
614 #if defined (_POSIX_PRIORITY_SCHEDULING) && (_POSIX_PRIORITY_SCHEDULING >= 0) \
615 && defined (_POSIX_THREAD_PRIORITY_SCHEDULING) \
616 && (_POSIX_THREAD_PRIORITY_SCHEDULING >= 0)
619 struct sched_param sp = { .sched_priority = priority + rt_offset, };
622 if (sp.sched_priority <= 0)
623 sp.sched_priority += sched_get_priority_max (policy = SCHED_OTHER);
625 sp.sched_priority += sched_get_priority_min (policy = SCHED_RR);
627 pthread_attr_setschedpolicy (attr, policy);
628 pthread_attr_setschedparam (attr, &sp);
634 /* The thread stack size.
635 * The lower the value, the less address space per thread, the highest
636 * maximum simultaneous threads per process. Too low values will cause
637 * stack overflows and weird crashes. Set with caution. Also keep in mind
638 * that 64-bits platforms consume more stack than 32-bits one.
640 * Thanks to on-demand paging, thread stack size only affects address space
641 * consumption. In terms of memory, threads only use what they need
642 * (rounded up to the page boundary).
644 * For example, on Linux i386, the default is 2 mega-bytes, which supports
645 * about 320 threads per processes. */
646 #define VLC_STACKSIZE (128 * sizeof (void *) * 1024)
649 ret = pthread_attr_setstacksize (attr, VLC_STACKSIZE);
650 assert (ret == 0); /* fails iif VLC_STACKSIZE is invalid */
653 ret = pthread_create (th, attr, entry, data);
654 pthread_sigmask (SIG_SETMASK, &oldset, NULL);
655 pthread_attr_destroy (attr);
660 * Creates and starts new thread.
662 * The thread must be <i>joined</i> with vlc_join() to reclaim resources
663 * when it is not needed anymore.
665 * @param th [OUT] pointer to write the handle of the created thread to
666 * (mandatory, must be non-NULL)
667 * @param entry entry point for the thread
668 * @param data data parameter given to the entry point
669 * @param priority thread priority value
670 * @return 0 on success, a standard error code on error.
672 int vlc_clone (vlc_thread_t *th, void *(*entry) (void *), void *data,
677 pthread_attr_init (&attr);
678 return vlc_clone_attr (th, &attr, entry, data, priority);
682 * Waits for a thread to complete (if needed), then destroys it.
683 * This is a cancellation point; in case of cancellation, the join does _not_
686 * A thread cannot join itself (normally VLC will abort if this is attempted).
687 * Also, a detached thread <b>cannot</b> be joined.
689 * @param handle thread handle
690 * @param p_result [OUT] pointer to write the thread return value or NULL
692 void vlc_join (vlc_thread_t handle, void **result)
694 int val = pthread_join (handle, result);
695 VLC_THREAD_ASSERT ("joining thread");
699 * Creates and starts new detached thread.
700 * A detached thread cannot be joined. Its resources will be automatically
701 * released whenever the thread exits (in particular, its call stack will be
704 * Detached thread are particularly useful when some work needs to be done
705 * asynchronously, that is likely to be completed much earlier than the thread
706 * can practically be joined. In this case, thread detach can spare memory.
708 * A detached thread may be cancelled, so as to expedite its termination.
709 * Be extremely careful if you do this: while a normal joinable thread can
710 * safely be cancelled after it has already exited, cancelling an already
711 * exited detached thread is undefined: The thread handle would is destroyed
712 * immediately when the detached thread exits. So you need to ensure that the
713 * detached thread is still running before cancellation is attempted.
715 * @warning Care must be taken that any resources used by the detached thread
716 * remains valid until the thread completes.
718 * @note A detached thread must eventually exit just like another other
719 * thread. In practice, LibVLC will wait for detached threads to exit before
720 * it unloads the plugins.
722 * @param th [OUT] pointer to hold the thread handle, or NULL
723 * @param entry entry point for the thread
724 * @param data data parameter given to the entry point
725 * @param priority thread priority value
726 * @return 0 on success, a standard error code on error.
728 int vlc_clone_detach (vlc_thread_t *th, void *(*entry) (void *), void *data,
737 pthread_attr_init (&attr);
738 pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
739 return vlc_clone_attr (th, &attr, entry, data, priority);
742 int vlc_set_priority (vlc_thread_t th, int priority)
744 #if defined (_POSIX_PRIORITY_SCHEDULING) && (_POSIX_PRIORITY_SCHEDULING >= 0) \
745 && defined (_POSIX_THREAD_PRIORITY_SCHEDULING) \
746 && (_POSIX_THREAD_PRIORITY_SCHEDULING >= 0)
749 struct sched_param sp = { .sched_priority = priority + rt_offset, };
752 if (sp.sched_priority <= 0)
753 sp.sched_priority += sched_get_priority_max (policy = SCHED_OTHER);
755 sp.sched_priority += sched_get_priority_min (policy = SCHED_RR);
757 if (pthread_setschedparam (th, policy, &sp))
761 (void) th; (void) priority;
767 * Marks a thread as cancelled. Next time the target thread reaches a
768 * cancellation point (while not having disabled cancellation), it will
769 * run its cancellation cleanup handler, the thread variable destructors, and
770 * terminate. vlc_join() must be used afterward regardless of a thread being
773 void vlc_cancel (vlc_thread_t thread_id)
775 pthread_cancel (thread_id);
779 * Save the current cancellation state (enabled or disabled), then disable
780 * cancellation for the calling thread.
781 * This function must be called before entering a piece of code that is not
782 * cancellation-safe, unless it can be proven that the calling thread will not
784 * @return Previous cancellation state (opaque value for vlc_restorecancel()).
786 int vlc_savecancel (void)
789 int val = pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
791 VLC_THREAD_ASSERT ("saving cancellation");
796 * Restore the cancellation state for the calling thread.
797 * @param state previous state as returned by vlc_savecancel().
798 * @return Nothing, always succeeds.
800 void vlc_restorecancel (int state)
805 val = pthread_setcancelstate (state, &oldstate);
806 /* This should fail if an invalid value for given for state */
807 VLC_THREAD_ASSERT ("restoring cancellation");
809 if (unlikely(oldstate != PTHREAD_CANCEL_DISABLE))
810 vlc_thread_fatal ("restoring cancellation while not disabled", EINVAL,
811 __func__, __FILE__, __LINE__);
813 pthread_setcancelstate (state, NULL);
818 * Issues an explicit deferred cancellation point.
819 * This has no effect if thread cancellation is disabled.
820 * This can be called when there is a rather slow non-sleeping operation.
821 * This is also used to force a cancellation point in a function that would
822 * otherwise "not always" be a one (block_FifoGet() is an example).
824 void vlc_testcancel (void)
826 pthread_testcancel ();
829 void vlc_control_cancel (int cmd, ...)
832 vlc_assert_unreachable ();
836 * Precision monotonic clock.
838 * In principles, the clock has a precision of 1 MHz. But the actual resolution
839 * may be much lower, especially when it comes to sleeping with mwait() or
840 * msleep(). Most general-purpose operating systems provide a resolution of
841 * only 100 to 1000 Hz.
843 * @warning The origin date (time value "zero") is not specified. It is
844 * typically the time the kernel started, but this is platform-dependent.
845 * If you need wall clock time, use gettimeofday() instead.
847 * @return a timestamp in microseconds.
851 #if (_POSIX_TIMERS > 0)
855 if (unlikely(clock_gettime (vlc_clock_id, &ts) != 0))
858 return (INT64_C(1000000) * ts.tv_sec) + (ts.tv_nsec / 1000);
863 if (unlikely(gettimeofday (&tv, NULL) != 0))
865 return (INT64_C(1000000) * tv.tv_sec) + tv.tv_usec;
872 * Waits until a deadline (possibly later due to OS scheduling).
873 * @param deadline timestamp to wait for (see mdate())
875 void mwait (mtime_t deadline)
877 #if (_POSIX_CLOCK_SELECTION > 0)
879 /* If the deadline is already elapsed, or within the clock precision,
880 * do not even bother the system timer. */
881 deadline -= vlc_clock_prec;
883 struct timespec ts = mtime_to_ts (deadline);
885 while (clock_nanosleep (vlc_clock_id, TIMER_ABSTIME, &ts, NULL) == EINTR);
888 deadline -= mdate ();
897 * Waits for an interval of time.
898 * @param delay how long to wait (in microseconds)
900 void msleep (mtime_t delay)
902 struct timespec ts = mtime_to_ts (delay);
904 #if (_POSIX_CLOCK_SELECTION > 0)
906 while (clock_nanosleep (vlc_clock_id, 0, &ts, &ts) == EINTR);
909 while (nanosleep (&ts, &ts) == -1)
910 assert (errno == EINTR);
918 * @return number of available (logical) CPUs.
920 unsigned vlc_GetCPUCount(void)
922 #if defined(HAVE_SCHED_GETAFFINITY)
926 if (sched_getaffinity (0, sizeof (cpu), &cpu) < 0)
929 return CPU_COUNT (&cpu);
931 #elif defined(__SunOS)
935 processor_info_t cpuinfo;
937 processorid_t *cpulist = malloc (sizeof (*cpulist) * sysconf(_SC_NPROCESSORS_MAX));
938 if (unlikely(cpulist == NULL))
941 if (pset_info(PS_MYID, &type, &numcpus, cpulist) == 0)
943 for (u_int i = 0; i < numcpus; i++)
944 if (processor_info (cpulist[i], &cpuinfo) == 0)
945 count += (cpuinfo.pi_state == P_ONLINE);
948 count = sysconf (_SC_NPROCESSORS_ONLN);
950 return count ? count : 1;
951 #elif defined(_SC_NPROCESSORS_CONF)
952 return sysconf(_SC_NPROCESSORS_CONF);
954 # warning "vlc_GetCPUCount is not implemented for your platform"