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authorPrarit Bhargava <prarit@redhat.com>2013-02-08 17:59:53 -0500
committerJohn Stultz <john.stultz@linaro.org>2013-02-08 15:07:05 -0800
commit84e345e4e209cbe796c88fa2ad1732d7121ec100 (patch)
treef73f35d0e72a6c6f3e4b3ef430608aca3a5e8d54 /kernel/time/ntp.c
parent6f16eebe1ff82176339a0439c98ebec9768b0ee2 (diff)
time, Fix setting of hardware clock in NTP code
At init time, if the system time is "warped" forward in warp_clock() it will differ from the hardware clock by sys_tz.tz_minuteswest. This time difference is not taken into account when ntp updates the hardware clock, and this causes the system time to jump forward by this offset every reboot. The kernel must take this offset into account when writing the system time to the hardware clock in the ntp code. This patch adds persistent_clock_is_local which indicates that an offset has been applied in warp_clock() and accounts for the "warp" before writing the hardware clock. x86 does not have this problem as rtc writes are software limited to a +/-15 minute window relative to the current rtc time. Other arches, such as powerpc, however do a full synchronization of the system time to the rtc and will see this problem. [v2]: generated against tip/timers/core Signed-off-by: Prarit Bhargava <prarit@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'kernel/time/ntp.c')
-rw-r--r--kernel/time/ntp.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 313b161504b7..b10a42bb0165 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -511,13 +511,17 @@ static void sync_cmos_clock(struct work_struct *work)
getnstimeofday(&now);
if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) {
+ struct timespec adjust = now;
+
fail = -ENODEV;
+ if (persistent_clock_is_local)
+ adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
#ifdef CONFIG_GENERIC_CMOS_UPDATE
- fail = update_persistent_clock(now);
+ fail = update_persistent_clock(adjust);
#endif
#ifdef CONFIG_RTC_SYSTOHC
if (fail == -ENODEV)
- fail = rtc_set_ntp_time(now);
+ fail = rtc_set_ntp_time(adjust);
#endif
}