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 "kernel/system.h"
  11
  12 #include <minix/endpoint.h>
  13 #include <assert.h>
  14
  15 #if USE_SETALARM
  16
  17 static void cause_alarm(minix_timer_t *tp);
  18
  19 /*===========================================================================*
  20  *                              do_setalarm                                  *
  21  *===========================================================================*/
  22 int do_setalarm(struct proc * caller, message * m_ptr)
  23 {
  24 /* A process requests a synchronous alarm, or wants to cancel its alarm. */
  25   long exp_time;                /* expiration time for this alarm */
  26   int use_abs_time;             /* use absolute or relative time */
  27   minix_timer_t *tp;                    /* the process' timer structure */
  28   clock_t uptime;               /* placeholder for current uptime */
  29
  30   /* Extract shared parameters from the request message. */
  31   exp_time = m_ptr->ALRM_EXP_TIME;      /* alarm's expiration time */
  32   use_abs_time = m_ptr->ALRM_ABS_TIME;  /* flag for absolute time */
  33   if (! (priv(caller)->s_flags & SYS_PROC)) return(EPERM);
  34
  35   /* Get the timer structure and set the parameters for this alarm. */
  36   tp = &(priv(caller)->s_alarm_timer);
  37   tmr_arg(tp)->ta_int = caller->p_endpoint;
  38   tp->tmr_func = cause_alarm;
  39
  40   /* Return the ticks left on the previous alarm. */
  41   uptime = get_monotonic();
  42   if ((tp->tmr_exp_time != TMR_NEVER) && (uptime < tp->tmr_exp_time) ) {
  43       m_ptr->ALRM_TIME_LEFT = (tp->tmr_exp_time - uptime);
  44   } else {
  45       m_ptr->ALRM_TIME_LEFT = 0;
  46   }
  47
  48   /* Finally, (re)set the timer depending on the expiration time. */
  49   if (exp_time == 0) {
  50       reset_kernel_timer(tp);
  51   } else {
  52       tp->tmr_exp_time = (use_abs_time) ? exp_time : exp_time + get_monotonic();
  53       set_kernel_timer(tp, tp->tmr_exp_time, tp->tmr_func);
  54   }
  55   return(OK);
  56 }
  57
  58 /*===========================================================================*
  59  *                              cause_alarm                                  *
  60  *===========================================================================*/
  61 static void cause_alarm(minix_timer_t *tp)
  62 {
  63 /* Routine called if a timer goes off and the process requested a synchronous
  64  * alarm. The process number is stored in timer argument 'ta_int'. Notify that
  65  * process with a notification message from CLOCK.
  66  */
  67   endpoint_t proc_nr_e = tmr_arg(tp)->ta_int;   /* get process number */
  68   mini_notify(proc_addr(CLOCK), proc_nr_e);     /* notify process */
  69 }
  70
  71 #endif /* USE_SETALARM */