minix/kernel/system/do_setalarm.c

/* The system call implemented in this file:
 *   m_type:	SYS_SETALARM 
 *
 * The parameters for this system call are:
 *    m2_l1:	ALRM_EXP_TIME		(alarm's expiration time)
 *    m2_i2:	ALRM_ABS_TIME		(expiration time is absolute?)
 *    m2_l1:	ALRM_TIME_LEFT		(return seconds left of previous)
 *
 * Changes:
 *    Aug 25, 2004   fully rewritten to clean up code  (Jorrit N. Herder)
 */

#include "../system.h"

#if USE_SETALARM

FORWARD _PROTOTYPE( void cause_alarm, (timer_t *tp) );

/*===========================================================================*
 *				do_setalarm				     *
 *===========================================================================*/
PUBLIC int do_setalarm(m_ptr)
message *m_ptr;			/* pointer to request message */
{
/* A process requests a synchronous alarm, or wants to cancel its alarm. */
  register struct proc *rp;	/* pointer to requesting process */
  int proc_nr;			/* which process wants the alarm */
  long exp_time;		/* expiration time for this alarm */
  int use_abs_time;		/* use absolute or relative time */
  timer_t *tp;			/* the process' timer structure */
  clock_t uptime;		/* placeholder for current uptime */

  /* Extract shared parameters from the request message. */
  exp_time = m_ptr->ALRM_EXP_TIME;	/* alarm's expiration time */
  use_abs_time = m_ptr->ALRM_ABS_TIME;	/* flag for absolute time */
  proc_nr = m_ptr->m_source;		/* process to interrupt later */
  rp = proc_addr(proc_nr);
  if (! (priv(rp)->s_flags & SYS_PROC)) return(EPERM);

  /* Get the timer structure and set the parameters for this alarm. */
  tp = &(priv(rp)->s_alarm_timer);	
  tmr_arg(tp)->ta_int = proc_nr;	
  tp->tmr_func = cause_alarm; 

  /* Return the ticks left on the previous alarm. */
  uptime = get_uptime(); 
  if ((tp->tmr_exp_time == TMR_NEVER) || (tp->tmr_exp_time < uptime) ) {
      m_ptr->ALRM_TIME_LEFT = 0;
  } else {
      m_ptr->ALRM_TIME_LEFT = (tp->tmr_exp_time - uptime);
  }

  /* Finally, (re)set the timer depending on the expiration time. */
  if (exp_time == 0) {
      reset_timer(tp);
  } else {
      tp->tmr_exp_time = (use_abs_time) ? exp_time : exp_time + get_uptime();
      set_timer(tp, tp->tmr_exp_time, tp->tmr_func);
  }
  return(OK);
}


/*===========================================================================*
 *				cause_alarm				     *
 *===========================================================================*/
PRIVATE void cause_alarm(tp)
timer_t *tp;
{
/* Routine called if a timer goes off and the process requested a synchronous
 * alarm. The process number is stored in timer argument 'ta_int'. Notify that
 * process with a notification message from CLOCK.
 */
  int proc_nr = tmr_arg(tp)->ta_int;		/* get process number */
  tmr_inittimer(tp);				/* reset alarm timer */
  lock_notify(CLOCK, proc_nr);			/* notify process */
}

#endif /* USE_SETALARM */