linux-kernel - Re: [PATCH v3] power: suspend: Move dpm_watchdog to suspend.c and enhance it

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Date:   Mon, 16 Nov 2020 18:18:11 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Joseph Jang <josephjang@...gle.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>, jonglin@...gle.com,
        woodylin@...gle.com, Mark Cheng <markcheng@...gle.com>
Subject: Re: [PATCH v3] power: suspend: Move dpm_watchdog to suspend.c and
 enhance it

On Fri, Nov 13, 2020 at 2:26 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Fri, Oct 23, 2020 at 02:04:17PM +0800, Joseph Jang wrote:
> > Since dpm_watchdog just cover device power management, we proposed to
> > move it to core power suspend.c to cover not only device power management
> > hang issues, but also core power management hand issues.
> >
> > Since dpm_watchdog stands for device pm, we propose to use new name sleep
> > timer and new timeout handler to cover more sleep hang issues. The new
> > timeout handler will dump disk sleep task at first round timeout and
> > trigger kernel panic at second round timeout.
> > The default timer for each round is defined in
> > CONFIG_PM_SLEEP_TIMER_TIMEOUT.
> >
> > Signed-off-by: Joseph Jang <josephjang@...gle.com>
>
> It still seems odd you can't use a watchdog for this, as you really have
> just implemented the same thing here, but "open coded" the logic.
>
> I'll let Rafael chime in here too, as he knows this area much better
> than I as to if this is viable or not.

It is viable AFAICS.

Just make the existing thing work with dev == NULL and use it as needed.