kernel/system/do_setalarm.c

   1 /* The kernel call implemented in this file:
   2  *   m_type:    SYS_SETALARM
   3  *
   4  * The parameters for this kernel call are:
   5  *    m2_l1:    ALRM_EXP_TIME           (alarm's expiration time)
   6  *    m2_i2:    ALRM_ABS_TIME           (expiration time is absolute?)
   7  *    m2_l1:    ALRM_TIME_LEFT          (return seconds left of previous)
   8  */
   9
  10 #include "../system.h"
  11
  12 #include <minix/endpoint.h>
  13
  14 #if USE_SETALARM
  15
  16 FORWARD _PROTOTYPE( void cause_alarm, (timer_t *tp) );
  17
  18 /*===========================================================================*
  19  *                              do_setalarm                                  *
  20  *===========================================================================*/
  21 PUBLIC int do_setalarm(m_ptr)
  22 message *m_ptr;                 /* pointer to request message */
  23 {
  24 /* A process requests a synchronous alarm, or wants to cancel its alarm. */
  25   register struct proc *rp;     /* pointer to requesting process */
  26   long exp_time;                /* expiration time for this alarm */
  27   int use_abs_time;             /* use absolute or relative time */
  28   timer_t *tp;                  /* the process' timer structure */
  29   clock_t uptime;               /* placeholder for current uptime */
  30
  31   /* Extract shared parameters from the request message. */
  32   exp_time = m_ptr->ALRM_EXP_TIME;      /* alarm's expiration time */
  33   use_abs_time = m_ptr->ALRM_ABS_TIME;  /* flag for absolute time */
  34   rp = proc_addr(who_p);
  35   if (! (priv(rp)->s_flags & SYS_PROC)) return(EPERM);
  36
  37   /* Get the timer structure and set the parameters for this alarm. */
  38   tp = &(priv(rp)->s_alarm_timer);
  39   tmr_arg(tp)->ta_int = m_ptr->m_source;
  40   tp->tmr_func = cause_alarm;
  41
  42   /* Return the ticks left on the previous alarm. */
  43   uptime = get_uptime();
  44   if ((tp->tmr_exp_time != TMR_NEVER) && (uptime < tp->tmr_exp_time) ) {
  45       m_ptr->ALRM_TIME_LEFT = (tp->tmr_exp_time - uptime);
  46   } else {
  47       m_ptr->ALRM_TIME_LEFT = 0;
  48   }
  49
  50   /* Finally, (re)set the timer depending on the expiration time. */
  51   if (exp_time == 0) {
  52       reset_timer(tp);
  53   } else {
  54       tp->tmr_exp_time = (use_abs_time) ? exp_time : exp_time + get_uptime();
  55       set_timer(tp, tp->tmr_exp_time, tp->tmr_func);
  56   }
  57   return(OK);
  58 }
  59
  60 /*===========================================================================*
  61  *                              cause_alarm                                  *
  62  *===========================================================================*/
  63 PRIVATE void cause_alarm(tp)
  64 timer_t *tp;
  65 {
  66 /* Routine called if a timer goes off and the process requested a synchronous
  67  * alarm. The process number is stored in timer argument 'ta_int'. Notify that
  68  * process with a notification message from CLOCK.
  69  */
  70   int proc_nr_e = tmr_arg(tp)->ta_int;          /* get process number */
  71   lock_notify(CLOCK, proc_nr_e);                /* notify process */
  72 }
  73
  74 #endif /* USE_SETALARM */