linux-kernel - Re: [PATCH] timekeeping: avoid adjust kernel time once hwclock kept in UTC time

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Date:	Wed, 20 Feb 2013 16:13:28 +0800
From:	Dong Zhu <bluezhudong@...il.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] timekeeping: avoid adjust kernel time once hwclock
 kept in UTC time

On Tue, Dec 18, 2012 at 10:37:08PM -0800, John Stultz wrote:
> On 12/18/2012 09:15 PM, Dong Zhu wrote:
> >On Thu, Dec 06, 2012 at 10:03:34PM +0800, Dong Zhu wrote:
> >> From c126376cf1837b0956e0268056db61870fbbc1d4 Mon Sep 17 00:00:00 2001
> >>From: Dong Zhu <bluezhudong@...il.com>
> >>Date: Thu, 6 Dec 2012 21:45:00 +0800
> >>Subject: [PATCH] timekeeping: avoid adjust kernel time once hwclock kept in
> >>  UTC time
> >>
> >>If the Hardware Clock kept in local time,kernel will adjust the time
> >>to be UTC time.But if Hardware Clock kept in UTC time,system will make
> >>a dummy settimeofday call first (sys_tz.tz_minuteswest = 0) to make sure
> >>the time is not shifted,so at this point I think maybe it is not necessary
> >>to set the kernel time once the sys_tz.tz_minuteswest is zero.
> >>
> >>Signed-off-by: Dong Zhu <bluezhudong@...il.com>
> >>---
> >>  kernel/time.c | 8 +++++---
> >>  1 file changed, 5 insertions(+), 3 deletions(-)
> >>
> >>diff --git a/kernel/time.c b/kernel/time.c
> >>index d226c6a..0b592ce 100644
> >>--- a/kernel/time.c
> >>+++ b/kernel/time.c
> >>@@ -134,9 +134,11 @@ static inline void warp_clock(void)
> >>  {
> >>  	struct timespec adjust;
> >>-	adjust = current_kernel_time();
> >>-	adjust.tv_sec += sys_tz.tz_minuteswest * 60;
> >>-	do_settimeofday(&adjust);
> >>+	if (sys_tz.tz_minuteswest) {
> >>+		adjust = current_kernel_time();
> >>+		adjust.tv_sec += sys_tz.tz_minuteswest * 60;
> >>+		do_settimeofday(&adjust);
> >>+	}
> >>  }
> >>  /*
> >>-- 
> >>1.7.11.7
> >>
> >Hi,
> >
> >Any comments ?
> Sorry for the slow response, been a little busy.   Honestly the
> warp_clock() code path is always been a bit odd to me, so I've not
> really been able to get my head around the implications of this
> change.
> 
> Really, I'm not sure if I'll get to this before the new year.
> Its on my list, but don't be afraid to ping me early Jan if I
> haven't queued it for 3.9 by then.
> 

Hi,

Distance my submit over a long time,whether my patch can be applied ?


-- 
Best Regards,
Dong Zhu
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