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Make the interval timings for EVFILT_TIMER more accurate. tvtohz() always

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adds an extra tick to account for the current partial clock tick.  However,
that is not appropriate for a repeating timer when the exact tvtohz() value
should be used for subsequent intervals.  Fix repeating callouts for
EVFILT_TIMER by subtracting 1 tick from the tvtohz() result similar to the
fix used in realitexpire() for interval timers.

While here, update a few comments to note that if the EVFILT_TIMER code
were to move out of kern_event.c, it should move to kern_time.c (where the
interval timer code it mimics lives) rather than kern_timeout.c.

MFC after:	1 month
This commit is contained in:
John Baldwin 2012-07-13 13:24:33 +00:00
parent 6f9cd2a9dc
commit 2919668490
1 changed files with 12 additions and 5 deletions
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17
sys/kern/kern_event.c
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@ -513,6 +513,10 @@ knote_fork(struct knlist *list, int pid)
list->kl_unlock(list->kl_lockarg);
}
/*
* XXX: EVFILT_TIMER should perhaps live in kern_time.c beside the
* interval timer support code.
*/
static int
timertoticks(intptr_t data)
{
@ -526,7 +530,6 @@ timertoticks(intptr_t data)
return tticks;
}
/* XXX - move to kern_timeout.c? */
static void
filt_timerexpire(void *knx)
{
@ -536,9 +539,16 @@ filt_timerexpire(void *knx)
kn->kn_data++;
KNOTE_ACTIVATE(kn, 0); /* XXX - handle locking */
/*
* timertoticks() uses tvtohz() which always adds 1 to allow
* for the time until the next clock interrupt being strictly
* less than 1 clock tick. We don't want that here since we
* want to appear to be in sync with the clock interrupt even
* when we're delayed.
*/
if ((kn->kn_flags & EV_ONESHOT) != EV_ONESHOT) {
calloutp = (struct callout *)kn->kn_hook;
callout_reset_curcpu(calloutp, timertoticks(kn->kn_sdata),
callout_reset_curcpu(calloutp, timertoticks(kn->kn_sdata) - 1,
filt_timerexpire, kn);
}
}
@ -546,7 +556,6 @@ filt_timerexpire(void *knx)
/*
* data contains amount of time to sleep, in milliseconds
*/
/* XXX - move to kern_timeout.c? */
static int
filt_timerattach(struct knote *kn)
{
@ -570,7 +579,6 @@ filt_timerattach(struct knote *kn)
return (0);
}
/* XXX - move to kern_timeout.c? */
static void
filt_timerdetach(struct knote *kn)
{
@ -583,7 +591,6 @@ filt_timerdetach(struct knote *kn)
kn->kn_status |= KN_DETACHED; /* knlist_remove usually clears it */
}
/* XXX - move to kern_timeout.c? */
static int
filt_timer(struct knote *kn, long hint)
{