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