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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. #include <sysinfo/sysinfo.h>
  52. #include <arch/barrier.h>
  53.  
  54. /* Pointers to public variables with time */
  55. struct ptime {
  56.     __native seconds1;
  57.     __native useconds;
  58.     __native seconds2;
  59. };
  60. struct ptime *public_time;
  61. /* Variable holding fragment of second, so that we would update
  62.  * seconds correctly
  63.  */
  64. static __native secfrag = 0;
  65.  
  66. /** Initialize realtime clock counter
  67.  *
  68.  * The applications (and sometimes kernel) need to access accurate
  69.  * information about realtime data. We allocate 1 page with these
  70.  * data and update it periodically.
  71.  *
  72.  *
  73.  */
  74. void clock_counter_init(void)
  75. {
  76.     void *faddr;
  77.  
  78.     faddr = (void *)PFN2ADDR(frame_alloc(0, FRAME_ATOMIC));
  79.     if (!faddr)
  80.         panic("Cannot allocate page for clock");
  81.    
  82.     public_time = (struct ptime *)PA2KA(faddr);
  83.  
  84.         /* TODO: We would need some arch dependent settings here */
  85.     public_time->seconds1 = 0;
  86.     public_time->seconds2 = 0;
  87.     public_time->useconds = 0;
  88.  
  89.     sysinfo_set_item_val("clock.faddr", NULL, (__native)faddr);
  90. }
  91.  
  92.  
  93. /** Update public counters
  94.  *
  95.  * Update it only on first processor
  96.  * TODO: Do we really need so many write barriers?
  97.  */
  98. static void clock_update_counters(void)
  99. {
  100.     if (CPU->id == 0) {
  101.         secfrag += 1000000/HZ;
  102.         if (secfrag >= 1000000) {
  103.             secfrag -= 1000000;
  104.             public_time->seconds1++;
  105.             write_barrier();
  106.             public_time->useconds = secfrag;
  107.             write_barrier();
  108.             public_time->seconds2 = public_time->seconds1;
  109.         } else
  110.             public_time->useconds += 1000000/HZ;
  111.     }
  112. }
  113.  
  114. /** Clock routine
  115.  *
  116.  * Clock routine executed from clock interrupt handler
  117.  * (assuming interrupts_disable()'d). Runs expired timeouts
  118.  * and preemptive scheduling.
  119.  *
  120.  */
  121. void clock(void)
  122. {
  123.     link_t *l;
  124.     timeout_t *h;
  125.     timeout_handler_t f;
  126.     void *arg;
  127.     int i;
  128.  
  129.     /*
  130.      * To avoid lock ordering problems,
  131.      * run all expired timeouts as you visit them.
  132.      */
  133.     for (i = 0; i <= CPU->missed_clock_ticks; i++) {
  134.         clock_update_counters();
  135.         spinlock_lock(&CPU->timeoutlock);
  136.         while ((l = CPU->timeout_active_head.next) != &CPU->timeout_active_head) {
  137.             h = list_get_instance(l, timeout_t, link);
  138.             spinlock_lock(&h->lock);
  139.             if (h->ticks-- != 0) {
  140.                 spinlock_unlock(&h->lock);
  141.                 break;
  142.             }
  143.             list_remove(l);
  144.             f = h->handler;
  145.             arg = h->arg;
  146.             timeout_reinitialize(h);
  147.             spinlock_unlock(&h->lock); 
  148.             spinlock_unlock(&CPU->timeoutlock);
  149.  
  150.             f(arg);
  151.  
  152.             spinlock_lock(&CPU->timeoutlock);
  153.         }
  154.         spinlock_unlock(&CPU->timeoutlock);
  155.     }
  156.     CPU->missed_clock_ticks = 0;
  157.  
  158.     /*
  159.      * Do CPU usage accounting and find out whether to preempt THREAD.
  160.      */
  161.  
  162.     if (THREAD) {
  163.         __u64 ticks;
  164.        
  165.         spinlock_lock(&CPU->lock);
  166.         CPU->needs_relink++;
  167.         spinlock_unlock(&CPU->lock);   
  168.    
  169.         spinlock_lock(&THREAD->lock);
  170.         if ((ticks = THREAD->ticks))
  171.             THREAD->ticks--;
  172.         spinlock_unlock(&THREAD->lock);
  173.        
  174.         if (!ticks && !PREEMPTION_DISABLED) {
  175.             scheduler();
  176.         }
  177.     }
  178.  
  179. }
  180.