lib/libsys/tickdelay.c

   1 #include "sysutil.h"
   2 #include <timers.h>
   3
   4 /*===========================================================================*
   5  *                               tickdelay                                   *
   6  *===========================================================================*/
   7 int tickdelay(ticks)
   8 long ticks;                             /* number of ticks to wait */
   9 {
  10 /* This function uses the synchronous alarm to delay for a while. This works
  11  * even if a previous synchronous alarm was scheduled, because the remaining
  12  * tick of the previous alarm are returned so that it can be rescheduled.
  13  * Note however that a long tick_delay (longer than the remaining time of the
  14  * previous) alarm will also delay the previous alarm.
  15  */
  16     message m, m_alarm;
  17     int s;
  18
  19     if (ticks <= 0) return OK;          /* check for robustness */
  20
  21     m.ALRM_EXP_TIME = ticks;            /* request message after ticks */
  22     m.ALRM_ABS_TIME = 0;                /* ticks are relative to now */
  23     s = _kernel_call(SYS_SETALARM, &m);
  24     if (s != OK) return(s);
  25
  26     sef_receive(CLOCK,&m_alarm);                /* await synchronous alarm */
  27
  28     /* Check if we must reschedule the current alarm. */
  29     if (m.ALRM_TIME_LEFT > 0 && m.ALRM_TIME_LEFT != TMR_NEVER) {
  30         m.ALRM_EXP_TIME = m.ALRM_TIME_LEFT - ticks;
  31         if (m.ALRM_EXP_TIME <= 0)
  32                 m.ALRM_EXP_TIME = 1;
  33         s = _kernel_call(SYS_SETALARM, &m);
  34     }
  35
  36     return(s);
  37 }
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