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  1. /*
  2.  * Copyright (C) 2001-2004 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /**
  30.  * @file    semaphore.c
  31.  * @brief   Semaphores.
  32.  */
  33.  
  34. #include <synch/semaphore.h>
  35. #include <synch/waitq.h>
  36. #include <synch/spinlock.h>
  37. #include <synch/synch.h>
  38. #include <arch/asm.h>
  39. #include <arch.h>
  40.  
  41. /** Initialize semaphore
  42.  *
  43.  * Initialize semaphore.
  44.  *
  45.  * @param s Semaphore.
  46.  * @param val Maximal number of threads allowed to enter critical section.
  47.  */
  48. void semaphore_initialize(semaphore_t *s, int val)
  49. {
  50.     ipl_t ipl;
  51.    
  52.     waitq_initialize(&s->wq);
  53.    
  54.     ipl = interrupts_disable();
  55.  
  56.     spinlock_lock(&s->wq.lock);
  57.     s->wq.missed_wakeups = val;
  58.     spinlock_unlock(&s->wq.lock);
  59.  
  60.     interrupts_restore(ipl);
  61. }
  62.  
  63. /** Semaphore down
  64.  *
  65.  * Semaphore down.
  66.  * Conditional mode and mode with timeout can be requested.
  67.  *
  68.  * @param s Semaphore.
  69.  * @param usec Timeout in microseconds.
  70.  * @param trydown Switches between blocking and non-blocking mode.
  71.  *
  72.  * For exact description of possible combinations of
  73.  * usec and trydown, see comment for waitq_sleep_timeout().
  74.  *
  75.  * @return See comment for waitq_sleep_timeout().
  76.  */
  77. int _semaphore_down_timeout(semaphore_t *s, __u32 usec, int trydown)
  78. {
  79.     return waitq_sleep_timeout(&s->wq, usec, trydown);
  80. }
  81.  
  82. /** Semaphore up
  83.  *
  84.  * Semaphore up.
  85.  *
  86.  * @param s Semaphore.
  87.  */
  88. void semaphore_up(semaphore_t *s)
  89. {
  90.     waitq_wakeup(&s->wq, WAKEUP_FIRST);
  91. }
  92.