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From: "Klein, Curtis" <curtis.klein@hpe.com>
To: Jiri Slaby <jirislaby@kernel.org>,
	Guenter Roeck <linux@roeck-us.net>,
	"wim@linux-watchdog.org" <wim@linux-watchdog.org>
Cc: "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>
Subject: RE: was [Re: [PATCH v3] watchdog: Add hrtimer-based pretimeout feature]
Date: Sun, 5 Sep 2021 22:22:26 +0000	[thread overview]
Message-ID: <CS1PR8401MB1270909863CE345530C9FFFB89D19@CS1PR8401MB1270.NAMPRD84.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <54d77fb1-2531-c6ed-738e-9f661443b097@kernel.org>

On 9/4/21, 1:19AM, Jiri Slaby wrote:
> On 04. 09. 21, 10:16, Jiri Slaby wrote:
> > On 02. 09. 21, 16:05, Guenter Roeck wrote:
> >> On 9/1/21 11:55 PM, Jiri Slaby wrote:
> >>> On 03. 02. 21, 21:11, Curtis Klein wrote:
> >>>> This adds the option to use a hrtimer to generate a watchdog pretimeout
> >>>> event for hardware watchdogs that do not natively support watchdog
> >>>> pretimeouts.
> >>>>
> >>>> With this enabled, all watchdogs will appear to have pretimeout support
> >>>> in userspace. If no pretimeout value is set, there will be no change in
> >>>> the watchdog's behavior.
> >>>
> >>> Hi,
> >>>
> >>> on my Dell Latitude 7280, CONFIG_WATCHDOG_HRTIMER_PRETIMEOUT=y causes
> >>> all reboot, kexec, suspend to panic. Disabling that option makes it
> >>> all work again. Provided it happens very late in the process, I don't
> >>> know how to grab some logs...
> >>>
> >>> Any ideas?
> >>>
> >>
> >> AFAICS the timer does not stop on reboot. I think we'll need to
> >> augment the code
> >> to do that.
> >
> > No, it is stopped via device unregister -> watchdog_dev_unregister ->
> > watchdog_cdev_unregister -> watchdog_hrtimer_pretimeout_stop.
> >
> > But look:
> > watchdog_cdev_unregister
> >    -> wdd->wd_data = NULL;
> >    -> watchdog_hrtimer_pretimeout_stop
> >      -> hrtimer_cancel(&wdd->wd_data->pretimeout_timer);
> >
> > The diff below obviously fixes the issue,
> 
> Which is exactly a -next commit:
> commit c7b178dae139f8857edc50888cfbf251cd974a38
> Author: Curtis Klein <curtis.klein@hpe.com>
> Date:   Tue Jun 22 23:26:23 2021 -0700
> 
>      watchdog: Fix NULL pointer dereference when releasing cdev
> 
> > --- a/drivers/watchdog/watchdog_dev.c
> > +++ b/drivers/watchdog/watchdog_dev.c
> > @@ -1096,6 +1096,8 @@ static void watchdog_cdev_unregister(struct
> > watchdog_device *wdd)
> >                  watchdog_stop(wdd);
> >          }
> >
> > +       watchdog_hrtimer_pretimeout_stop(wdd);
> > +
> >          mutex_lock(&wd_data->lock);
> >          wd_data->wdd = NULL;
> >          wdd->wd_data = NULL;
> > @@ -1103,7 +1105,6 @@ static void watchdog_cdev_unregister(struct
> > watchdog_device *wdd)
> >
> >          hrtimer_cancel(&wd_data->timer);
> >          kthread_cancel_work_sync(&wd_data->work);
> > -       watchdog_hrtimer_pretimeout_stop(wdd);
> >
> >          put_device(&wd_data->dev);
> >   }
> >
> > thanks,
> 
> 
> --
> js
> suse labs

Does it still make sense to stop the timer on reboot or suspend?

I haven't had any problems with rebooting but I haven't been able to test
suspending.

-Curtis

  parent reply	other threads:[~2021-09-05 22:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-03 20:11 [PATCH v3] watchdog: Add hrtimer-based pretimeout feature Curtis Klein
2021-02-04  1:35 ` Guenter Roeck
2021-09-02  6:55 ` Jiri Slaby
2021-09-02 14:05   ` Guenter Roeck
2021-09-04  8:16     ` was [Re: [PATCH v3] watchdog: Add hrtimer-based pretimeout feature] Jiri Slaby
     [not found]       ` <54d77fb1-2531-c6ed-738e-9f661443b097@kernel.org>
2021-09-05 22:22         ` Klein, Curtis [this message]
2021-09-05 22:56           ` Guenter Roeck

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