lib/libsys/timers.c

   1 /* Watchdog timer management. These functions in this file provide a
   2  * 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  *
   6  * The entry points into this file are:
   7  *   init_timer:     initialize a timer structure
   8  *   set_timer:      reset and existing or set a new watchdog timer
   9  *   cancel_timer:   remove a timer from the list of timers
  10  *   expire_timers:  check for expired timers and run watchdog functions
  11  *
  12  */
  13
  14 #include "syslib.h"
  15 #include <timers.h>
  16 #include <minix/sysutil.h>
  17
  18 static timer_t *timers = NULL;
  19 static int expiring = 0;
  20
  21 /*===========================================================================*
  22  *                              init_timer                                   *
  23  *===========================================================================*/
  24 void init_timer(timer_t *tp)
  25 {
  26         tmr_inittimer(tp);
  27 }
  28
  29 /*===========================================================================*
  30  *                              set_timer                                    *
  31  *===========================================================================*/
  32 void set_timer(timer_t *tp, int ticks, tmr_func_t watchdog, int arg)
  33 {
  34         int r;
  35         clock_t now, prev_time = 0, next_time;
  36
  37         if ((r = getuptime(&now)) != OK)
  38                 panic("set_timer: couldn't get uptime");
  39
  40         /* Set timer argument and add timer to the list. */
  41         tmr_arg(tp)->ta_int = arg;
  42         prev_time = tmrs_settimer(&timers, tp, now+ticks, watchdog, &next_time);
  43
  44         /* Reschedule our synchronous alarm if necessary. */
  45         if (expiring == 0 && (! prev_time || prev_time > next_time)) {
  46                 if (sys_setalarm(next_time, 1) != OK)
  47                         panic("set_timer: couldn't set alarm");
  48         }
  49 }
  50
  51 /*===========================================================================*
  52  *                              cancel_timer                                 *
  53  *===========================================================================*/
  54 void cancel_timer(timer_t *tp)
  55 {
  56         clock_t next_time, prev_time;
  57         prev_time = tmrs_clrtimer(&timers, tp, &next_time);
  58
  59         /* If the earliest timer has been removed, we have to set the alarm to
  60          * the next timer, or cancel the alarm altogether if the last timer
  61          * has been cancelled (next_time will be 0 then).
  62          */
  63         if (expiring == 0 && (prev_time < next_time || ! next_time)) {
  64                 if (sys_setalarm(next_time, 1) != OK)
  65                         panic("cancel_timer: couldn't set alarm");
  66         }
  67 }
  68
  69 /*===========================================================================*
  70  *                              expire_timers                                *
  71  *===========================================================================*/
  72 void expire_timers(clock_t now)
  73 {
  74         clock_t next_time;
  75
  76         /* Check for expired timers. Use a global variable to indicate that
  77          * watchdog functions are called, so that sys_setalarm() isn't called
  78          * more often than necessary when set_timer or cancel_timer are called
  79          * from these watchdog functions. */
  80         expiring = 1;
  81         tmrs_exptimers(&timers, now, &next_time);
  82         expiring = 0;
  83
  84         /* Reschedule an alarm if necessary. */
  85         if (next_time > 0) {
  86                 if (sys_setalarm(next_time, 1) != OK)
  87                         panic("expire_timers: couldn't set alarm");
  88         }
  89 }