Linux Audio

Check our new training course

Loading...
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
/* Helper code for POSIX timer implementation on LinuxThreads.
   Copyright (C) 2000, 2001, 2002, 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Kaz Kylheku <kaz@ashi.footprints.net>.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If
   not, see <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sysdep.h>
#include <time.h>
#include <unistd.h>
#include <sys/syscall.h>

#include "posix-timer.h"


/* Number of threads used.  */
#define THREAD_MAXNODES	16

/* Array containing the descriptors for the used threads.  */
static struct thread_node thread_array[THREAD_MAXNODES];

/* Static array with the structures for all the timers.  */
struct timer_node __timer_array[TIMER_MAX];

/* Global lock to protect operation on the lists.  */
pthread_mutex_t __timer_mutex = PTHREAD_MUTEX_INITIALIZER;

/* Variable to protext initialization.  */
pthread_once_t __timer_init_once_control = PTHREAD_ONCE_INIT;

/* Nonzero if initialization of timer implementation failed.  */
int __timer_init_failed;

/* Node for the thread used to deliver signals.  */
struct thread_node __timer_signal_thread_rclk;

/* Lists to keep free and used timers and threads.  */
struct list_links timer_free_list;
struct list_links thread_free_list;
struct list_links thread_active_list;


#ifdef __NR_rt_sigqueueinfo
extern int __syscall_rt_sigqueueinfo (int, int, siginfo_t *);
#endif


/* List handling functions.  */
static __inline__ void
list_init (struct list_links *list)
{
  list->next = list->prev = list;
}

static __inline__ void
list_append (struct list_links *list, struct list_links *newp)
{
  newp->prev = list->prev;
  newp->next = list;
  list->prev->next = newp;
  list->prev = newp;
}

static __inline__ void
list_insbefore (struct list_links *list, struct list_links *newp)
{
  list_append (list, newp);
}

/*
 * Like list_unlink_ip, except that calling it on a node that
 * is already unlinked is disastrous rather than a noop.
 */

static __inline__ void
list_unlink (struct list_links *list)
{
  struct list_links *lnext = list->next, *lprev = list->prev;

  lnext->prev = lprev;
  lprev->next = lnext;
}

static __inline__ struct list_links *
list_first (struct list_links *list)
{
  return list->next;
}

static __inline__ struct list_links *
list_null (struct list_links *list)
{
  return list;
}

static __inline__ struct list_links *
list_next (struct list_links *list)
{
  return list->next;
}

static __inline__ int
list_isempty (struct list_links *list)
{
  return list->next == list;
}


/* Functions build on top of the list functions.  */
static __inline__ struct thread_node *
thread_links2ptr (struct list_links *list)
{
  return (struct thread_node *) ((char *) list
				 - offsetof (struct thread_node, links));
}

static __inline__ struct timer_node *
timer_links2ptr (struct list_links *list)
{
  return (struct timer_node *) ((char *) list
				- offsetof (struct timer_node, links));
}


/* Initialize a newly allocated thread structure.  */
static void
thread_init (struct thread_node *thread, const pthread_attr_t *attr, clockid_t clock_id)
{
  if (attr != NULL)
    thread->attr = *attr;
  else
    {
      pthread_attr_init (&thread->attr);
      pthread_attr_setdetachstate (&thread->attr, PTHREAD_CREATE_DETACHED);
    }

  thread->exists = 0;
  list_init (&thread->timer_queue);
  pthread_cond_init (&thread->cond, 0);
  thread->current_timer = 0;
  thread->captured = pthread_self ();
  thread->clock_id = clock_id;
}


/* Initialize the global lists, and acquire global resources.  Error
   reporting is done by storing a non-zero value to the global variable
   timer_init_failed.  */
static void
init_module (void)
{
  int i;

  list_init (&timer_free_list);
  list_init (&thread_free_list);
  list_init (&thread_active_list);

  for (i = 0; i < TIMER_MAX; ++i)
    {
      list_append (&timer_free_list, &__timer_array[i].links);
      __timer_array[i].inuse = TIMER_FREE;
    }

  for (i = 0; i < THREAD_MAXNODES; ++i)
    list_append (&thread_free_list, &thread_array[i].links);

  thread_init (&__timer_signal_thread_rclk, 0, CLOCK_REALTIME);
}


/* This is a handler executed in a child process after a fork()
   occurs.  It reinitializes the module, resetting all of the data
   structures to their initial state.  The mutex is initialized in
   case it was locked in the parent process.  */
static void
reinit_after_fork (void)
{
  init_module ();
  pthread_mutex_init (&__timer_mutex, 0);
}


/* Called once form pthread_once in timer_init. This initializes the
   module and ensures that reinit_after_fork will be executed in any
   child process.  */
void
__timer_init_once (void)
{
  init_module ();
  pthread_atfork (0, 0, reinit_after_fork);
}


/* Deinitialize a thread that is about to be deallocated.  */
static void
thread_deinit (struct thread_node *thread)
{
  assert (list_isempty (&thread->timer_queue));
  pthread_cond_destroy (&thread->cond);
}


/* Allocate a thread structure from the global free list.  Global
   mutex lock must be held by caller.  The thread is moved to
   the active list. */
struct thread_node *
__timer_thread_alloc (const pthread_attr_t *desired_attr, clockid_t clock_id)
{
  struct list_links *node = list_first (&thread_free_list);

  if (node != list_null (&thread_free_list))
    {
      struct thread_node *thread = thread_links2ptr (node);
      list_unlink (node);
      thread_init (thread, desired_attr, clock_id);
      list_append (&thread_active_list, node);
      return thread;
    }

  return 0;
}


/* Return a thread structure to the global free list.  Global lock
   must be held by caller.  */
void
__timer_thread_dealloc (struct thread_node *thread)
{
  thread_deinit (thread);
  list_unlink (&thread->links);
  list_append (&thread_free_list, &thread->links);
}


/* Each of our threads which terminates executes this cleanup
   handler. We never terminate threads ourselves; if a thread gets here
   it means that the evil application has killed it.  If the thread has
   timers, these require servicing and so we must hire a replacement
   thread right away.  We must also unblock another thread that may
   have been waiting for this thread to finish servicing a timer (see
   timer_delete()).  */

static void
thread_cleanup (void *val)
{
  if (val != NULL)
    {
      struct thread_node *thread = val;

      /* How did the signal thread get killed?  */
      assert (thread != &__timer_signal_thread_rclk);

      pthread_mutex_lock (&__timer_mutex);

      thread->exists = 0;

      /* We are no longer processing a timer event.  */
      thread->current_timer = 0;

      if (list_isempty (&thread->timer_queue))
	  __timer_thread_dealloc (thread);
      else
	(void) __timer_thread_start (thread);

      pthread_mutex_unlock (&__timer_mutex);

      /* Unblock potentially blocked timer_delete().  */
      pthread_cond_broadcast (&thread->cond);
    }
}


/* Handle a timer which is supposed to go off now.  */
static void
thread_expire_timer (struct thread_node *self, struct timer_node *timer)
{
  self->current_timer = timer; /* Lets timer_delete know timer is running. */

  pthread_mutex_unlock (&__timer_mutex);

  switch (__builtin_expect (timer->event.sigev_notify, SIGEV_SIGNAL))
    {
    case SIGEV_NONE:
      break;

    case SIGEV_SIGNAL:
#ifdef __NR_rt_sigqueueinfo
      {
	siginfo_t info;

	/* First, clear the siginfo_t structure, so that we don't pass our
	   stack content to other tasks.  */
	memset (&info, 0, sizeof (siginfo_t));
	/* We must pass the information about the data in a siginfo_t
           value.  */
	info.si_signo = timer->event.sigev_signo;
	info.si_code = SI_TIMER;
	info.si_pid = timer->creator_pid;
	info.si_uid = getuid ();
	info.si_value = timer->event.sigev_value;

	INLINE_SYSCALL (rt_sigqueueinfo, 3, info.si_pid, info.si_signo, &info);
      }
#else
      if (pthread_kill (self->captured, timer->event.sigev_signo) != 0)
	{
	  if (pthread_kill (self->id, timer->event.sigev_signo) != 0)
	    abort ();
        }
#endif
      break;

    case SIGEV_THREAD:
      timer->event.sigev_notify_function (timer->event.sigev_value);
      break;

    default:
      assert (! "unknown event");
      break;
    }

  pthread_mutex_lock (&__timer_mutex);

  self->current_timer = 0;

  pthread_cond_broadcast (&self->cond);
}


/* Thread function; executed by each timer thread. The job of this
   function is to wait on the thread's timer queue and expire the
   timers in chronological order as close to their scheduled time as
   possible.  */
static void
__attribute__ ((noreturn))
thread_func (void *arg)
{
  struct thread_node *self = arg;

  /* Register cleanup handler, in case rogue application terminates
     this thread.  (This cannot happen to __timer_signal_thread, which
     doesn't invoke application callbacks). */

  pthread_cleanup_push (thread_cleanup, self);

  pthread_mutex_lock (&__timer_mutex);

  while (1)
    {
      struct list_links *first;
      struct timer_node *timer = NULL;

      /* While the timer queue is not empty, inspect the first node.  */
      first = list_first (&self->timer_queue);
      if (first != list_null (&self->timer_queue))
	{
	  struct timespec now;

	  timer = timer_links2ptr (first);

	  /* This assumes that the elements of the list of one thread
	     are all for the same clock.  */
	  clock_gettime (timer->clock, &now);

	  while (1)
	    {
	      /* If the timer is due or overdue, remove it from the queue.
		 If it's a periodic timer, re-compute its new time and
		 requeue it.  Either way, perform the timer expiry. */
	      if (timespec_compare (&now, &timer->expirytime) < 0)
		break;

	      list_unlink_ip (first);

	      if (__builtin_expect (timer->value.it_interval.tv_sec, 0) != 0
		  || timer->value.it_interval.tv_nsec != 0)
		{
		  timer->overrun_count = 0;
		  timespec_add (&timer->expirytime, &timer->expirytime,
				&timer->value.it_interval);
		  while (timespec_compare (&timer->expirytime, &now) < 0)
		    {
		      timespec_add (&timer->expirytime, &timer->expirytime,
				    &timer->value.it_interval);
		      if (timer->overrun_count < DELAYTIMER_MAX)
			++timer->overrun_count;
		    }
		  __timer_thread_queue_timer (self, timer);
		}

	      thread_expire_timer (self, timer);

	      first = list_first (&self->timer_queue);
	      if (first == list_null (&self->timer_queue))
		break;

	      timer = timer_links2ptr (first);
	    }
	}

      /* If the queue is not empty, wait until the expiry time of the
	 first node.  Otherwise wait indefinitely.  Insertions at the
	 head of the queue must wake up the thread by broadcasting
	 this condition variable.  */
      if (timer != NULL)
	pthread_cond_timedwait (&self->cond, &__timer_mutex,
				&timer->expirytime);
      else
	pthread_cond_wait (&self->cond, &__timer_mutex);
    }
  /* This macro will never be executed since the while loop loops
     forever - but we have to add it for proper nesting.  */
  pthread_cleanup_pop (1);
}


/* Enqueue a timer in wakeup order in the thread's timer queue.
   Returns 1 if the timer was inserted at the head of the queue,
   causing the queue's next wakeup time to change. */

int
__timer_thread_queue_timer (struct thread_node *thread,
			    struct timer_node *insert)
{
  struct list_links *iter;
  int athead = 1;

  for (iter = list_first (&thread->timer_queue);
       iter != list_null (&thread->timer_queue);
        iter = list_next (iter))
    {
      struct timer_node *timer = timer_links2ptr (iter);

      if (timespec_compare (&insert->expirytime, &timer->expirytime) < 0)
	  break;
      athead = 0;
    }

  list_insbefore (iter, &insert->links);
  return athead;
}


/* Start a thread and associate it with the given thread node.  Global
   lock must be held by caller.  */
int
__timer_thread_start (struct thread_node *thread)
{
  int retval = 1;

  assert (!thread->exists);
  thread->exists = 1;

  if (pthread_create (&thread->id, &thread->attr,
		      (void *(*) (void *)) thread_func, thread) != 0)
    {
      thread->exists = 0;
      retval = -1;
    }

  return retval;
}


void
__timer_thread_wakeup (struct thread_node *thread)
{
  pthread_cond_broadcast (&thread->cond);
}


/* Compare two pthread_attr_t thread attributes for exact equality.
   Returns 1 if they are equal, otherwise zero if they are not equal or
   contain illegal values.  This version is LinuxThreads-specific for
   performance reason.  One could use the access functions to get the
   values of all the fields of the attribute structure.  */
static int
thread_attr_compare (const pthread_attr_t *left, const pthread_attr_t *right)
{
  return (left->__detachstate == right->__detachstate
	  && left->__schedpolicy == right->__schedpolicy
	  && left->__guardsize == right->__guardsize
	  && (left->__schedparam.sched_priority
	      == right->__schedparam.sched_priority)
	  && left->__inheritsched == right->__inheritsched
	  && left->__scope == right->__scope
	  && left->__stacksize == right->__stacksize
	  && left->__stackaddr_set == right->__stackaddr_set
	  && (left->__stackaddr_set
	      || left->__stackaddr == right->__stackaddr));
}


/* Search the list of active threads and find one which has matching
   attributes.  Global mutex lock must be held by caller.  */
struct thread_node *
__timer_thread_find_matching (const pthread_attr_t *desired_attr,
			      clockid_t desired_clock_id)
{
  struct list_links *iter = list_first (&thread_active_list);

  while (iter != list_null (&thread_active_list))
    {
      struct thread_node *candidate = thread_links2ptr (iter);

      if (thread_attr_compare (desired_attr, &candidate->attr)
	  && desired_clock_id == candidate->clock_id)
	return candidate;

      iter = list_next (iter);
    }

  return NULL;
}


/* Grab a free timer structure from the global free list.  The global
   lock must be held by the caller.  */
struct timer_node *
__timer_alloc (void)
{
  struct list_links *node = list_first (&timer_free_list);

  if (node != list_null (&timer_free_list))
    {
      struct timer_node *timer = timer_links2ptr (node);
      list_unlink_ip (node);
      timer->inuse = TIMER_INUSE;
      timer->refcount = 1;
      return timer;
    }

  return NULL;
}


/* Return a timer structure to the global free list.  The global lock
   must be held by the caller.  */
void
__timer_dealloc (struct timer_node *timer)
{
  assert (timer->refcount == 0);
  timer->thread = NULL;	/* Break association between timer and thread.  */
  timer->inuse = TIMER_FREE;
  list_append (&timer_free_list, &timer->links);
}


/* Thread cancellation handler which unlocks a mutex.  */
void
__timer_mutex_cancel_handler (void *arg)
{
  pthread_mutex_unlock (arg);
}