minix/lib/utils/tickdelay.c
2005-06-06 14:58:47 +00:00

44 lines
1.4 KiB
C

#include "utils.h"
/*===========================================================================*
* tickdelay *
*===========================================================================*/
PUBLIC int tickdelay(ticks)
long ticks; /* number of ticks to wait */
{
/* This function uses the synchronous alarm to delay for a while. This works
* even if a previous synchronous alarm was scheduled, because the remaining
* tick of the previous alarm are returned so that it can be rescheduled.
* Note however that a long tick_delay (longer than the remaining time of the
* previous) alarm will also delay the previous alarm.
*/
message m, m_alarm;
clock_t time_left;
int s;
if (ticks <= 0) return; /* check for robustness */
m.m_type = SYS_SYNCALRM; /* request a synchronous alarm */
m.ALRM_PROC_NR = SELF; /* SELF means this process nr */
m.ALRM_EXP_TIME = ticks; /* request message after ticks */
m.ALRM_ABS_TIME = 0; /* ticks are relative to now */
s = _taskcall(SYSTASK, SYS_SYNCALRM, &m);
if (s != OK) return(s);
receive(CLOCK,&m_alarm); /* await synchronous alarm */
/* Check if we must reschedule the current alarm. */
if (m.ALRM_TIME_LEFT > 0) {
m.ALRM_EXP_TIME = m.ALRM_TIME_LEFT - ticks;
if (m.ALRM_EXP_TIME <= 0)
m.ALRM_EXP_TIME = 1;
s = _taskcall(SYSTASK, SYS_SYNCALRM, &m);
}
return(s);
}