Re: [RFE PATCH 1/2] x86, rtc, ntp, Do full rtc synchronization withntp

From: John Stultz
Date: Fri Feb 22 2013 - 15:43:14 EST

On 02/14/2013 09:02 AM, Prarit Bhargava wrote:
Every 11 minutes ntp attempts to update the x86 rtc with the current
system time. Currently, the x86 code only updates the rtc if the system
time is within +/-15 minutes of the current value of the rtc. Other
architectures do a full synchronization and there is no reason that x86
should be software limited to a 30 minute window.

This patch changes the behavior of the kernel to do a full synchronization
(year, month, day, hour, minute, and second) of the rtc when ntp requests
a synchronization between the system time and the rtc.

I've used the RTC library functions in this patchset as they do all the
required bounds checking.

Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: Matt Fleming <matt.fleming@xxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: linux-efi@xxxxxxxxxxxxxxx

This looks reasonable to me.

Though I want to make sure we get this thoroughly tested by the various distros so we don't surprise anyone, since it has to potential to cause problems where folks are dualbooting windows (using a localtime RTC) and do not have their OS setup to trigger warp_clock to adjust for the localtime rtc (instead getting a time correction later via NTP).

I'll queue it and see about getting it merged to -tip & -next. Then we'll have to decide if 3.10 or 3.11 is the right time frame to land it.


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