linux-kernel - Re: [PATCH] timekeeping: Use proper timekeeper for debug code

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Message-ID: <20170706035855.GA2511@lianli.shorne-pla.net>
Date:   Thu, 6 Jul 2017 12:58:55 +0900
From:   Stafford Horne <shorne@...il.com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH] timekeeping: Use proper timekeeper for debug code

Hi tglx,

Sorry, to bother you, I thought maybe this you missed this one?  Let me
know if you want a resend.

-Stafford

On Wed, Jun 28, 2017 at 10:39:21AM -0700, John Stultz wrote:
> On Wed, Jun 28, 2017 at 6:21 AM, Stafford Horne <shorne@...il.com> wrote:
> > When CONFIG_DEBUG_TIMEKEEPING is enabled the timekeeping_check_update()
> > function will update status like last_warning and underflow_seen on the
> > timekeeper.
> >
> > If there are issues found this state is used to rate limit the warnings
> > that get printed.
> >
> > This rate limiting doesn't really really work if stored in real_tk as
> > the shadow timekeeper is overwritten onto real_tk at the end of every
> > update_wall_time() call, resetting last_warning and other statuses.
> >
> > Fix rate limiting by using the shadow_timekeeper for
> > timekeeping_check_update().
> >
> > Fixes: commit 57d05a93ada7 ("time: Rework debugging variables so they aren't global")
> > Signed-off-by: Stafford Horne <shorne@...il.com>
> 
> Interesting!  Thanks for submitting this! Out of curiosity, can you
> also talk about the underlying issue that made you come across this
> issue?
> 
> thanks
> -john