servers/pm/timers.c

   1 /* PM watchdog timer management. These functions in this file provide
   2  * a convenient interface to the timers library that manages a list of
   3  * watchdog timers. All details of scheduling an alarm at the CLOCK task
   4  * are hidden behind this interface.
   5  * Only system processes are allowed to set an alarm timer at the kernel.
   6  * Therefore, the PM maintains a local list of timers for user processes
   7  * that requested an alarm signal.
   8  *
   9  * The entry points into this file are:
  10  *   pm_set_timer:      reset and existing or set a new watchdog timer
  11  *   pm_expire_timers:  check for expired timers and run watchdog functions
  12  *   pm_cancel_timer:   remove a time from the list of timers
  13  *
  14  */
  15
  16 #include "pm.h"
  17
  18 #include <timers.h>
  19 #include <minix/syslib.h>
  20 #include <minix/com.h>
  21
  22 PRIVATE timer_t *pm_timers = NULL;
  23
  24 /*===========================================================================*
  25  *                              pm_set_timer                                 *
  26  *===========================================================================*/
  27 PUBLIC void pm_set_timer(timer_t *tp, int ticks, tmr_func_t watchdog, int arg)
  28 {
  29         int r;
  30         clock_t now, prev_time = 0, next_time;
  31
  32         if ((r = getuptime(&now)) != OK)
  33                 panic(__FILE__, "PM couldn't get uptime", NO_NUM);
  34
  35         /* Set timer argument and add timer to the list. */
  36         tmr_arg(tp)->ta_int = arg;
  37         prev_time = tmrs_settimer(&pm_timers,tp,now+ticks,watchdog,&next_time);
  38
  39         /* Reschedule our synchronous alarm if necessary. */
  40         if (! prev_time || prev_time > next_time) {
  41                 if (sys_setalarm(next_time, 1) != OK)
  42                         panic(__FILE__, "PM set timer couldn't set alarm.", NO_NUM);
  43         }
  44
  45         return;
  46 }
  47
  48 /*===========================================================================*
  49  *                              pm_expire_timers                             *
  50  *===========================================================================*/
  51 PUBLIC void pm_expire_timers(clock_t now)
  52 {
  53         clock_t next_time;
  54
  55         /* Check for expired timers and possibly reschedule an alarm. */
  56         tmrs_exptimers(&pm_timers, now, &next_time);
  57         if (next_time > 0) {
  58                 if (sys_setalarm(next_time, 1) != OK)
  59                         panic(__FILE__, "PM expire timer couldn't set alarm.", NO_NUM);
  60         }
  61 }
  62
  63 /*===========================================================================*
  64  *                              pm_cancel_timer                              *
  65  *===========================================================================*/
  66 PUBLIC void pm_cancel_timer(timer_t *tp)
  67 {
  68         clock_t next_time, prev_time;
  69         prev_time = tmrs_clrtimer(&pm_timers, tp, &next_time);
  70
  71         /* If the earliest timer has been removed, we have to set the alarm to
  72      * the next timer, or cancel the alarm altogether if the last timer has
  73      * been cancelled (next_time will be 0 then).
  74          */
  75         if (prev_time < next_time || ! next_time) {
  76                 if (sys_setalarm(next_time, 1) != OK)
  77                         panic(__FILE__, "PM expire timer couldn't set alarm.", NO_NUM);
  78         }
  79 }