[PATCH 5.4 026/183] timekeeping: Fix cross-timestamp interpolation on counter wrap

Sasha Levin
2024-03-24T23:47:05Z

From: Peter Hilber <peter.hilber@opensynergy.com>

[ Upstream commit 84dccadd3e2a3f1a373826ad71e5ced5e76b0c00 ]

cycle_between() decides whether get_device_system_crosststamp() will
interpolate for older counter readings.

cycle_between() yields wrong results for a counter wrap-around where after
< before < test, and for the case after < test < before.

Fix the comparison logic.

Fixes: 2c756feb18d9 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/20231218073849.35294-2-peter.hilber@opensynergy.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/time/timekeeping.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 105dd0b663291..5ae2b5b5ce4a0 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1099,7 +1099,7 @@ static bool cycle_between(u64 before, u64 test, u64 after)
{
if (test > before && test < after)
return true;
- if (test < before && before > after)
+ if (before > after && (test > before || test < after))
return true;
return false;
}
--
2.43.0