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

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Date:   Wed, 28 Jun 2017 10:39:21 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Stafford Horne <shorne@...il.com>
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

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