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Explicitly compute the next interval using 64bit arithmetic, if the time 

was either stepped backwards or the timer has overflown. This fixes
PR 26470.
This commit is contained in:
joerg 2008-05-29 15:27:51 +00:00
parent c2b95373bf
commit 157262cae8
1 changed files with 37 additions and 20 deletions
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57
sys/kern/kern_time.c
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@ -1,4 +1,4 @@
/* $NetBSD: kern_time.c,v 1.147 2008/05/08 18:56:58 ad Exp $ */
/* $NetBSD: kern_time.c,v 1.148 2008/05/29 15:27:51 joerg Exp $ */
/*-
* Copyright (c) 2000, 2004, 2005, 2007, 2008 The NetBSD Foundation, Inc.
@ -61,7 +61,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_time.c,v 1.147 2008/05/08 18:56:58 ad Exp $");
__KERNEL_RCSID(0, "$NetBSD: kern_time.c,v 1.148 2008/05/29 15:27:51 joerg Exp $");
#include <sys/param.h>
#include <sys/resourcevar.h>
@ -923,8 +923,10 @@ sys_timer_getoverrun(struct lwp *l, const struct sys_timer_getoverrun_args *uap,
void
realtimerexpire(void *arg)
{
struct timeval now;
uint64_t last_val, next_val, interval, now_ms;
struct timeval now, next;
struct ptimer *pt;
int backwards;
pt = arg;
@ -936,24 +938,39 @@ realtimerexpire(void *arg)
mutex_spin_exit(&timer_lock);
return;
}
for (;;) {
timeradd(&pt->pt_time.it_value,
&pt->pt_time.it_interval, &pt->pt_time.it_value);
getmicrotime(&now);
if (timercmp(&pt->pt_time.it_value, &now, >)) {
/*
* Don't need to check hzto() return value, here.
* callout_reset() does it for us.
*/
callout_reset(&pt->pt_ch, hzto(&pt->pt_time.it_value),
realtimerexpire, pt);
mutex_spin_exit(&timer_lock);
return;
}
mutex_spin_exit(&timer_lock);
pt->pt_overruns++;
mutex_spin_enter(&timer_lock);
getmicrotime(&now);
backwards = (timercmp(&pt->pt_time.it_value, &now, >));
timeradd(&pt->pt_time.it_value, &pt->pt_time.it_interval, &next);
/* Handle the easy case of non-overflown timers first. */
if (!backwards && timercmp(&next, &now, >)) {
pt->pt_time.it_value = next;
} else {
#define TV2MS(x) (((uint64_t)(x)->tv_sec) * 1000000 + (x)->tv_usec)
now_ms = TV2MS(&now);
last_val = TV2MS(&pt->pt_time.it_value);
interval = TV2MS(&pt->pt_time.it_interval);
#undef TV2MS
next_val = now_ms +
(now_ms - last_val + interval - 1) % interval;
if (backwards)
next_val += interval;
else
pt->pt_overruns += (now_ms - last_val) / interval;
pt->pt_time.it_value.tv_sec = next_val / 1000000;
pt->pt_time.it_value.tv_usec = next_val % 1000000;
}
/*
* Don't need to check hzto() return value, here.
* callout_reset() does it for us.
*/
callout_reset(&pt->pt_ch, hzto(&pt->pt_time.it_value),
realtimerexpire, pt);
mutex_spin_exit(&timer_lock);
}
/* BSD routine to get the value of an interval timer. */