minix/servers/pm/timers.c

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/* PM watchdog timer management. These functions in this file provide
* a convenient interface to the timers library that manages a list of
* watchdog timers. All details of scheduling an alarm at the CLOCK task
* are hidden behind this interface.
* Only system processes are allowed to set an alarm timer at the kernel.
* Therefore, the PM maintains a local list of timers for user processes
* that requested an alarm signal.
*
* The entry points into this file are:
* pm_set_timer: reset and existing or set a new watchdog timer
* pm_expire_timers: check for expired timers and run watchdog functions
* pm_cancel_timer: remove a time from the list of timers
*
*/
#include "pm.h"
#include <timers.h>
#include <minix/syslib.h>
#include <minix/com.h>
PRIVATE timer_t *pm_timers = NULL;
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PRIVATE int pm_expiring = 0;
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/*===========================================================================*
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* pm_set_timer *
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*===========================================================================*/
PUBLIC void pm_set_timer(timer_t *tp, int ticks, tmr_func_t watchdog, int arg)
{
int r;
clock_t now, prev_time = 0, next_time;
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if ((r = getuptime(&now)) != OK)
panic("PM couldn't get uptime");
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/* Set timer argument and add timer to the list. */
tmr_arg(tp)->ta_int = arg;
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prev_time = tmrs_settimer(&pm_timers,tp,now+ticks,watchdog,&next_time);
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/* Reschedule our synchronous alarm if necessary. */
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if (pm_expiring == 0 && (! prev_time || prev_time > next_time)) {
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if (sys_setalarm(next_time, 1) != OK)
panic("PM set timer couldn't set alarm");
}
return;
}
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/*===========================================================================*
* pm_expire_timers *
*===========================================================================*/
PUBLIC void pm_expire_timers(clock_t now)
{
clock_t next_time;
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/* Check for expired timers. Use a global variable to indicate that
* watchdog functions are called, so that sys_setalarm() isn't called
* more often than necessary when pm_set_timer or pm_cancel_timer are
* called from these watchdog functions. */
pm_expiring = 1;
tmrs_exptimers(&pm_timers, now, &next_time);
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pm_expiring = 0;
/* Reschedule an alarm if necessary. */
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if (next_time > 0) {
if (sys_setalarm(next_time, 1) != OK)
panic("PM expire timer couldn't set alarm");
}
}
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/*===========================================================================*
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* pm_cancel_timer *
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*===========================================================================*/
PUBLIC void pm_cancel_timer(timer_t *tp)
{
clock_t next_time, prev_time;
prev_time = tmrs_clrtimer(&pm_timers, tp, &next_time);
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/* If the earliest timer has been removed, we have to set the alarm to
* the next timer, or cancel the alarm altogether if the last timer has
* been cancelled (next_time will be 0 then).
*/
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if (pm_expiring == 0 && (prev_time < next_time || ! next_time)) {
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if (sys_setalarm(next_time, 1) != OK)
panic("PM expire timer couldn't set alarm");
}
}