minix/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  *    m_lsys_krn_sys_setalarm.exp_time          (alarm's expiration time)
   6  *    m_lsys_krn_sys_setalarm.abs_time          (expiration time is absolute?)
   7  *    m_lsys_krn_sys_setalarm.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(int proc_nr_e);
  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->m_lsys_krn_sys_setalarm.exp_time;
  32   use_abs_time = m_ptr->m_lsys_krn_sys_setalarm.abs_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
  38   /* Return the ticks left on the previous alarm. */
  39   uptime = get_monotonic();
  40   if (!tmr_is_set(tp)) {
  41         m_ptr->m_lsys_krn_sys_setalarm.time_left = TMR_NEVER;
  42   } else if (tmr_is_first(uptime, tp->tmr_exp_time)) {
  43         m_ptr->m_lsys_krn_sys_setalarm.time_left = tp->tmr_exp_time - uptime;
  44   } else {
  45         m_ptr->m_lsys_krn_sys_setalarm.time_left = 0;
  46   }
  47
  48   /* For the caller's convenience, also return the current time. */
  49   m_ptr->m_lsys_krn_sys_setalarm.uptime = uptime;
  50
  51   /*
  52    * Finally, (re)set the timer depending on the expiration time.  Note that
  53    * an absolute time of zero is as valid as any other absolute value, so only
  54    * a relative time value of zero resets the timer.
  55    */
  56   if (!use_abs_time && exp_time == 0) {
  57         reset_kernel_timer(tp);
  58   } else {
  59         if (!use_abs_time)
  60                 exp_time += uptime;
  61         set_kernel_timer(tp, exp_time, cause_alarm, caller->p_endpoint);
  62   }
  63   return(OK);
  64 }
  65
  66 /*===========================================================================*
  67  *                              cause_alarm                                  *
  68  *===========================================================================*/
  69 static void cause_alarm(int proc_nr_e)
  70 {
  71 /* Routine called if a timer goes off and the process requested a synchronous
  72  * alarm. The process number is stored as the timer argument. Notify that
  73  * process with a notification message from CLOCK.
  74  */
  75   mini_notify(proc_addr(CLOCK), proc_nr_e);     /* notify process */
  76 }
  77
  78 #endif /* USE_SETALARM */