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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    clock.c
  31.  * @brief   High-level clock interrupt handler.
  32.  *
  33.  * This file contains the clock() function which is the source
  34.  * of preemption. It is also responsible for executing expired
  35.  * timeouts.
  36.  */
  37.  
  38. #include <time/clock.h>
  39. #include <time/timeout.h>
  40. #include <arch/types.h>
  41. #include <config.h>
  42. #include <synch/spinlock.h>
  43. #include <synch/waitq.h>
  44. #include <func.h>
  45. #include <proc/scheduler.h>
  46. #include <cpu.h>
  47. #include <arch.h>
  48. #include <adt/list.h>
  49. #include <atomic.h>
  50. #include <proc/thread.h>
  51.  
  52. /** Clock routine
  53.  *
  54.  * Clock routine executed from clock interrupt handler
  55.  * (assuming interrupts_disable()'d). Runs expired timeouts
  56.  * and preemptive scheduling.
  57.  *
  58.  */
  59. void clock(void)
  60. {
  61.     link_t *l;
  62.     timeout_t *h;
  63.     timeout_handler_t f;
  64.     void *arg;
  65.     int i;
  66.  
  67.     /*
  68.      * To avoid lock ordering problems,
  69.      * run all expired timeouts as you visit them.
  70.      */
  71.     for (i = 0; i < CPU->missed_clock_ticks; i++) {
  72.         spinlock_lock(&CPU->timeoutlock);
  73.         while ((l = CPU->timeout_active_head.next) != &CPU->timeout_active_head) {
  74.             h = list_get_instance(l, timeout_t, link);
  75.             spinlock_lock(&h->lock);
  76.             if (h->ticks-- != 0) {
  77.                 spinlock_unlock(&h->lock);
  78.                 break;
  79.             }
  80.             list_remove(l);
  81.             f = h->handler;
  82.             arg = h->arg;
  83.             timeout_reinitialize(h);
  84.             spinlock_unlock(&h->lock); 
  85.             spinlock_unlock(&CPU->timeoutlock);
  86.  
  87.             f(arg);
  88.  
  89.             spinlock_lock(&CPU->timeoutlock);
  90.         }
  91.         spinlock_unlock(&CPU->timeoutlock);
  92.     }
  93.     CPU->missed_clock_ticks = 0;
  94.  
  95.     /*
  96.      * Do CPU usage accounting and find out whether to preempt THREAD.
  97.      */
  98.  
  99.     if (THREAD) {
  100.         __u64 ticks;
  101.        
  102.         spinlock_lock(&CPU->lock);
  103.         CPU->needs_relink++;
  104.         spinlock_unlock(&CPU->lock);   
  105.    
  106.         spinlock_lock(&THREAD->lock);
  107.         if ((ticks = THREAD->ticks))
  108.             THREAD->ticks--;
  109.         spinlock_unlock(&THREAD->lock);
  110.        
  111.         if (!ticks && !PREEMPTION_DISABLED) {
  112.             scheduler();
  113.         }
  114.     }
  115.  
  116. }
  117.