linux-kernel - Re: [PATCH] timekeeping: Add missing update call in timekeeping

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Message-ID: <5005206E.9040804@openvz.org>
Date:	Tue, 17 Jul 2012 12:21:02 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	John Stultz <johnstul@...ibm.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Prarit Bhargava <prarit@...hat.com>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] timekeeping: Add missing update call in timekeeping_resume()

I run into the same regression in s2ram between v3.5-rc6 and v3.5-rc7.
This patch helps. Thanks.

Tested-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>

John Stultz wrote:
> From: Thomas Gleixner<tglx@...utronix.de>
>
> Linus,
> 	Since Thomas is on vacation I wanted to send you his fix to resolve
> the suspend regression from the leapsecond fixes.
>
> thanks
> -john
>
> The leap second rework unearthed another issue of inconsistent data.
>
> On timekeeping_resume() the timekeeper data is updated, but nothing
> calls timekeeping_update(), so now the update code in the timer
> interrupt sees stale values.
>
> This has been the case before those changes, but then the timer
> interrupt was using stale data as well so this went unnoticed for
> quite some time.
>
> Add the missing update call, so all the data is consistent everywhere.
>
> Reported-by: Andreas Schwab<schwab@...ux-m68k.org>
> Reported-by-and-tested-by: "Rafael J. Wysocki"<rjw@...k.pl>
> CC: LKML<linux-kernel@...r.kernel.org>
> Cc: Linux PM list<linux-pm@...r.kernel.org>
> Cc: John Stultz<johnstul@...ibm.com>
> Cc: Ingo Molnar<mingo@...nel.org>
> Cc: Peter Zijlstra<a.p.zijlstra@...llo.nl>,
> Cc: Prarit Bhargava<prarit@...hat.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Thomas Gleixner<tglx@...utronix.de>
> Signed-off-by: John Stultz<johnstul@...ibm.com>
> ---
>   kernel/time/timekeeping.c |    1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 269b1fe..3447cfa 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -717,6 +717,7 @@ static void timekeeping_resume(void)
>   	timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
>   	timekeeper.ntp_error = 0;
>   	timekeeping_suspended = 0;
> +	timekeeping_update(false);
>   	write_sequnlock_irqrestore(&timekeeper.lock, flags);
>
>   	touch_softlockup_watchdog();

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