linux-kernel - Re: [PATCH] Fix half-Y2K38 problem in timecompare

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Message-ID: <2375c9f90909292235p7c21776aodd855a4ffa82afa8@mail.gmail.com>
Date:	Wed, 30 Sep 2009 13:35:34 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Barry Song <21cnbao@...il.com>
Cc:	akpm@...ux-foundation.org, davem@...emloft.net,
	patrick.ohly@...el.com, uclinux-dist-devel@...ckfin.uclinux.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Fix half-Y2K38 problem in timecompare_update while 
	calculating offset

On Mon, Sep 28, 2009 at 6:16 PM, Barry Song <21cnbao@...il.com> wrote:
> ktime will overflow from 03:14:07 UTC on Tuesday, 19 January 2038,
> ktime_add() in timecompare_update() will overflow a half earlier.
> As a result, wrong offset will be gotten, then cause some strange
> problems.
> ---
>  kernel/time/timecompare.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/time/timecompare.c b/kernel/time/timecompare.c
> index 71e7f1a..d2d893e 100644
> --- a/kernel/time/timecompare.c
> +++ b/kernel/time/timecompare.c
> @@ -89,7 +89,7 @@ int timecompare_offset(struct timecompare *sync,
>                         * source time
>                         */
>                        sample.offset =
> -                               ktime_to_ns(ktime_add(end, start)) / 2 -
> +                               (ktime_to_ns(end) + ktime_to_ns(start)) / 2 -
>                                ts;
>
>                        /* simple insertion sort based on duration */

Just please add your Signed-off-by.

I think you catch the right thing, so

Acked-by: WANG Cong <xiyou.wangcong@...il.com>

Add Cc: Thomas Gleixner <tglx@...utronix.de>.
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