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authorMiroslav Lichvar <mlichvar@redhat.com>2019-04-17 10:48:33 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-22 08:17:14 +0200
commit5ab0886e03e48abe0ea0e8c9aabbd0ca533dafb3 (patch)
tree8eb2f751240d4bfac93dfac6329b7b820899b700 /kernel/time
parentd7541cb8df432cc60676f1be6d59044d944151e8 (diff)
ntp: Allow TAI-UTC offset to be set to zero
[ Upstream commit fdc6bae940ee9eb869e493990540098b8c0fd6ab ] The ADJ_TAI adjtimex mode sets the TAI-UTC offset of the system clock. It is typically set by NTP/PTP implementations and it is automatically updated by the kernel on leap seconds. The initial value is zero (which applications may interpret as unknown), but this value cannot be set by adjtimex. This limitation seems to go back to the original "nanokernel" implementation by David Mills. Change the ADJ_TAI check to accept zero as a valid TAI-UTC offset in order to allow setting it back to the initial value. Fixes: 153b5d054ac2 ("ntp: support for TAI") Suggested-by: Ondrej Mosnacek <omosnace@redhat.com> Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Prarit Bhargava <prarit@redhat.com> Link: https://lkml.kernel.org/r/20190417084833.7401-1-mlichvar@redhat.com Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/ntp.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 6df8927c58a5..0a16419006f3 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -639,7 +639,7 @@ static inline void process_adjtimex_modes(struct timex *txc,
time_constant = max(time_constant, 0l);
}
- if (txc->modes & ADJ_TAI && txc->constant > 0)
+ if (txc->modes & ADJ_TAI && txc->constant >= 0)
*time_tai = txc->constant;
if (txc->modes & ADJ_OFFSET)