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Change the sign on a race-condition, so that instead of ending up several

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tens of milliseconds out in the future we end up the right place with
a subweeniesecond error.
This commit is contained in:
Poul-Henning Kamp 1998-07-04 19:12:21 +00:00
parent 5089aede57
commit 0edd53d22a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=37382
2 changed files with 36 additions and 16 deletions
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26
sys/kern/kern_clock.c
View File

@ -39,7 +39,7 @@ static volatile int print_tci = 1;
* SUCH DAMAGE.
*
* @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
* $Id: kern_clock.c,v 1.73 1998/06/09 13:10:52 phk Exp $
* $Id: kern_clock.c,v 1.74 1998/07/02 21:35:02 phk Exp $
*/
#include <sys/param.h>
@ -747,15 +747,14 @@ switch_timecounter(struct timecounter *newtc)
static struct timecounter *
sync_other_counter(void)
{
struct timecounter *tc, *tco;
struct timecounter *tc, *tcn, *tco;
unsigned delta;
if (timecounter->tc_poll_pps)
timecounter->tc_poll_pps(timecounter);
tc = timecounter->tc_other;
tco = tc->tc_other;
*tc = *timecounter;
tc->tc_other = tco;
tco = timecounter;
tc = tco->tc_other;
tcn = tc->tc_other;
*tc = *tco;
tc->tc_other = tcn;
delta = tco_delta(tc);
tc->tc_offset_count += delta;
tc->tc_offset_count &= tc->tc_counter_mask;
@ -770,6 +769,17 @@ tco_forward(void)
struct timecounter *tc;
tc = sync_other_counter();
/*
* We may be inducing a tiny error here, the tc_poll_pps() may
* process a latched count which happens after the tco_delta()
* in sync_other_counter(), which would extend the previous
* counters parameters into the domain of this new one.
* Since the timewindow is very small for this, the error is
* going to be only a few weenieseconds (as Dave Mills would
* say), so lets just not talk more about it, OK ?
*/
if (tc->tc_poll_pps)
tc->tc_poll_pps(tc);
if (timedelta != 0) {
tc->tc_offset_nano += (u_int64_t)(tickdelta * 1000) << 32;
timedelta -= tickdelta;

26
sys/kern/kern_tc.c
View File

@ -39,7 +39,7 @@ static volatile int print_tci = 1;
* SUCH DAMAGE.
*
* @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
* $Id: kern_clock.c,v 1.73 1998/06/09 13:10:52 phk Exp $
* $Id: kern_clock.c,v 1.74 1998/07/02 21:35:02 phk Exp $
*/
#include <sys/param.h>
@ -747,15 +747,14 @@ switch_timecounter(struct timecounter *newtc)
static struct timecounter *
sync_other_counter(void)
{
struct timecounter *tc, *tco;
struct timecounter *tc, *tcn, *tco;
unsigned delta;
if (timecounter->tc_poll_pps)
timecounter->tc_poll_pps(timecounter);
tc = timecounter->tc_other;
tco = tc->tc_other;
*tc = *timecounter;
tc->tc_other = tco;
tco = timecounter;
tc = tco->tc_other;
tcn = tc->tc_other;
*tc = *tco;
tc->tc_other = tcn;
delta = tco_delta(tc);
tc->tc_offset_count += delta;
tc->tc_offset_count &= tc->tc_counter_mask;
@ -770,6 +769,17 @@ tco_forward(void)
struct timecounter *tc;
tc = sync_other_counter();
/*
* We may be inducing a tiny error here, the tc_poll_pps() may
* process a latched count which happens after the tco_delta()
* in sync_other_counter(), which would extend the previous
* counters parameters into the domain of this new one.
* Since the timewindow is very small for this, the error is
* going to be only a few weenieseconds (as Dave Mills would
* say), so lets just not talk more about it, OK ?
*/
if (tc->tc_poll_pps)
tc->tc_poll_pps(tc);
if (timedelta != 0) {
tc->tc_offset_nano += (u_int64_t)(tickdelta * 1000) << 32;
timedelta -= tickdelta;