A think-o in the calculation of the monotonic -> tai time offset
results in CLOCK_TAI timers and nanosleeps to expire late (the
latency is ~2x the tai offset).

Fix this by adding the tai offset from the realtime offset instead
of subtracting.

Cc: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: stable <[email protected]> #3.10+
Signed-off-by: John Stultz <[email protected]>
---
 kernel/time/timekeeping.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index c1d36b6..a4c5742 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -77,7 +77,7 @@ static void tk_set_wall_to_mono(struct timekeeper *tk, struct 
timespec wtm)
        tk->wall_to_monotonic = wtm;
        set_normalized_timespec(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
        tk->offs_real = timespec_to_ktime(tmp);
-       tk->offs_tai = ktime_sub(tk->offs_real, ktime_set(tk->tai_offset, 0));
+       tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tk->tai_offset, 0));
 }
 
 static void tk_set_sleep_time(struct timekeeper *tk, struct timespec t)
@@ -595,7 +595,7 @@ s32 timekeeping_get_tai_offset(void)
 static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
 {
        tk->tai_offset = tai_offset;
-       tk->offs_tai = ktime_sub(tk->offs_real, ktime_set(tai_offset, 0));
+       tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));
 }
 
 /**
-- 
1.8.3.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Reply via email to