6.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paul E. McKenney <paulmck@xxxxxxxxxx>
[ Upstream commit e40806e9bcf8aaa86dbf0d484e7cf3cfa09cb86c ]
The nanosecond-to-millisecond skew computation uses unsigned arithmetic,
which produces user-unfriendly large positive numbers for negative skews.
Therefore, use signed arithmetic for this computation in order to preserve
the negativity.
Reported-by: Chris Bainbridge <chris.bainbridge@xxxxxxxxx>
Reported-by: Feng Tang <feng.tang@xxxxxxxxx>
Fixes: dd029269947a ("clocksource: Improve "skew is too large" messages")
Reviewed-by: Feng Tang <feng.tang@xxxxxxxxx>
Tested-by: Chris Bainbridge <chris.bainbridge@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/time/clocksource.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 91836b727cef5..0600e16dbafef 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -473,8 +473,8 @@ static void clocksource_watchdog(struct timer_list *unused)
/* Check the deviation from the watchdog clocksource. */
md = cs->uncertainty_margin + watchdog->uncertainty_margin;
if (abs(cs_nsec - wd_nsec) > md) {
- u64 cs_wd_msec;
- u64 wd_msec;
+ s64 cs_wd_msec;
+ s64 wd_msec;
u32 wd_rem;
pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
@@ -483,8 +483,8 @@ static void clocksource_watchdog(struct timer_list *unused)
watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
cs->name, cs_nsec, csnow, cslast, cs->mask);
- cs_wd_msec = div_u64_rem(cs_nsec - wd_nsec, 1000U * 1000U, &wd_rem);
- wd_msec = div_u64_rem(wd_nsec, 1000U * 1000U, &wd_rem);
+ cs_wd_msec = div_s64_rem(cs_nsec - wd_nsec, 1000 * 1000, &wd_rem);
+ wd_msec = div_s64_rem(wd_nsec, 1000 * 1000, &wd_rem);
pr_warn(" Clocksource '%s' skewed %lld ns (%lld ms) over watchdog '%s' interval of %lld ns (%lld ms)\n",
cs->name, cs_nsec - wd_nsec, cs_wd_msec, watchdog->name, wd_nsec, wd_msec);
if (curr_clocksource == cs)
--
2.40.1
