linux-kernel - Re: [PATCH] watchdog: sbsa_gwdt: add shutdown hook to driver

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Date:   Thu, 27 Aug 2020 09:52:40 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Qiang Zhao <qiang.zhao@....com>
Cc:     "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] watchdog: sbsa_gwdt: add shutdown hook to driver

On Thu, Aug 27, 2020 at 07:55:31AM +0000, Qiang Zhao wrote:
> On 8/24/20 21:29 AM, Guenter Roeck <linux@...ck-us.net> wrote:
> 
> > -----Original Message-----
> > From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
> > Sent: 2020年8月24日 21:29
> > To: Qiang Zhao <qiang.zhao@....com>; wim@...ux-watchdog.org
> > Cc: linux-watchdog@...r.kernel.org; linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH] watchdog: sbsa_gwdt: add shutdown hook to driver
> > 
> > On 8/24/20 1:18 AM, Qiang Zhao wrote:
> > > From: Zhao Qiang <qiang.zhao@....com>
> > >
> > > Kexec maybe need more time than timeout of wdt(sbsa) which will reset
> > > the system.
> > > So it is necessary to add shutdown hook to disable the wdt when run
> > > kexec.
> > >
> > 
> > Please explain why watchdog_stop_on_reboot() does not work.
> > 
> 
> Thank you for your comments, it is helpful.
> I investigate this issue again, found that this watchdog are enabled by uboot,
> Meanwhile in kernel, it is not the default watchdog, in another words, it is not active in kernel.
> So watchdog_stop_on_reboot() does not work.
> This patch is not the right solution for the situation, I will abandon it. 

Yes, it is the wrong solution. watchdog_reboot_notifier() needs to be
fixed instead: It needs to check check if the hardware watchdog is running
(not if it is active). Also, the reboot notifier should only be registered
if the stop callback exists (and otherwise bail out with an error).

Thanks,
Guenter