linux-kernel - Re: [PATCH v2 1/1] kernel/watchdog: always restore watchdog_softlockup(,hardlockup)_user

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Message-ID: <CAD=FV=VGt-M-CGBOWDc1a3g-t2mUyHkCQ1TFcgvrUbmJDyV0Mg@mail.gmail.com>
Date: Wed, 11 Sep 2024 15:35:57 -0700
From: Doug Anderson <dianders@...omium.org>
To: dianders@...omium.org, akpm@...ux-foundation.org, bristot@...hat.com, 
	bsegall@...gle.com, dietmar.eggemann@....com, john.ogness@...utronix.de, 
	juri.lelli@...hat.com, kjlx@...pleofstupid.com, linux-kernel@...r.kernel.org, 
	linux@...ssschuh.net, lizhe.67@...edance.com, mcgrof@...nel.org, 
	mgorman@...e.de, mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org, 
	tglx@...utronix.de, vincent.guittot@...aro.org, vschneid@...hat.com, 
	zyhtheonly@...il.com, zyhtheonly@...h.net
Cc: tiozhang@...iglobal.com
Subject: Re: [PATCH v2 1/1] kernel/watchdog: always restore
 watchdog_softlockup(,hardlockup)_user_enabled after proc show

Hi,

On Fri, Sep 6, 2024 at 2:47 AM Tio Zhang <tiozhang@...iglobal.com> wrote:
>
> Otherwise when watchdog_enabled becomes 0,
> watchdog_softlockup(,hardlockup)_user_enabled will changes to 0 after
> proc show.
>
> Steps to reproduce:
>
>   step 1:
>   # cat /proc/sys/kernel/*watchdog
>   1
>   1
>   1
>
>   | name                             | value
>   |----------------------------------|--------------------------
>   | watchdog_enabled                 | 1
>   |----------------------------------|--------------------------
>   | watchdog_hardlockup_user_enabled | 1
>   |----------------------------------|--------------------------
>   | watchdog_softlockup_user_enabled | 1
>   |----------------------------------|--------------------------
>   | watchdog_user_enabled            | 1
>   |----------------------------------|--------------------------
>
>   step 2:
>   # echo 0 > /proc/sys/kernel/watchdog
>
>   | name                             | value
>   |----------------------------------|--------------------------
>   | watchdog_enabled                 | 0
>   |----------------------------------|--------------------------
>   | watchdog_hardlockup_user_enabled | 1
>   |----------------------------------|--------------------------
>   | watchdog_softlockup_user_enabled | 1
>   |----------------------------------|--------------------------
>   | watchdog_user_enabled            | 0
>   |----------------------------------|--------------------------
>
>   step 3:
>   # cat /proc/sys/kernel/*watchdog
>   0
>   0
>   0
>
>   | name                             | value
>   |----------------------------------|--------------------------
>   | watchdog_enabled                 | 0
>   |----------------------------------|--------------------------
>   | watchdog_hardlockup_user_enabled | 0
>   |----------------------------------|--------------------------
>   | watchdog_softlockup_user_enabled | 0
>   |----------------------------------|--------------------------
>   | watchdog_user_enabled            | 0
>   |----------------------------------|--------------------------
>
>   step 4:
>   # echo 1 > /proc/sys/kernel/watchdog
>
>   | name                             | value
>   |----------------------------------|--------------------------
>   | watchdog_enabled                 | 0
>   |----------------------------------|--------------------------
>   | watchdog_hardlockup_user_enabled | 0
>   |----------------------------------|--------------------------
>   | watchdog_softlockup_user_enabled | 0
>   |----------------------------------|--------------------------
>   | watchdog_user_enabled            | 0
>   |----------------------------------|--------------------------
>
>   step 5:
>   # cat /proc/sys/kernel/*watchdog
>   0
>   0
>   0
>
> If we dont do "step 3", do "step 4" right after "step 2", it will be
>
>   | name                             | value
>   |----------------------------------|--------------------------
>   | watchdog_enabled                 | 1
>   |----------------------------------|--------------------------
>   | watchdog_hardlockup_user_enabled | 1
>   |----------------------------------|--------------------------
>   | watchdog_softlockup_user_enabled | 1
>   |----------------------------------|--------------------------
>   | watchdog_user_enabled            | 1
>   |----------------------------------|--------------------------
>
> then everything works correctly.
>
> So this patch fix "step 3"'s value into
>
> | name                             | value
> |----------------------------------|--------------------------
> | watchdog_enabled                 | 0
> |----------------------------------|--------------------------
> | watchdog_hardlockup_user_enabled | 1
> |----------------------------------|--------------------------
> | watchdog_softlockup_user_enabled | 1
> |----------------------------------|--------------------------
> | watchdog_user_enabled            | 0
> |----------------------------------|--------------------------
>
> And still print 0 as before.
>
> Signed-off-by: Tio Zhang <tiozhang@...iglobal.com>
> ---
>  kernel/watchdog.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

The description is pretty verbose but also much clearer. The patch
looks good to me now.

Reviewed-by: Douglas Anderson <dianders@...omium.org>