minix/lib/libsys/tickdelay.c

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#include "sysutil.h"
#include <timers.h>
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/*===========================================================================*
* tickdelay *
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*===========================================================================*/
int tickdelay(clock_t ticks)
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{
/* 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;
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int s;
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if (ticks <= 0) return OK; /* check for robustness */
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m.ALRM_EXP_TIME = ticks; /* request message after ticks */
m.ALRM_ABS_TIME = 0; /* ticks are relative to now */
s = _kernel_call(SYS_SETALARM, &m);
if (s != OK) return(s);
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sef_receive(CLOCK,&m_alarm); /* await synchronous alarm */
/* Check if we must reschedule the current alarm. */
if (m.ALRM_TIME_LEFT > 0 && m.ALRM_TIME_LEFT != TMR_NEVER) {
m.ALRM_EXP_TIME = m.ALRM_TIME_LEFT - ticks;
if (m.ALRM_EXP_TIME <= 0)
m.ALRM_EXP_TIME = 1;
s = _kernel_call(SYS_SETALARM, &m);
}
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return(s);
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}