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From: Jiri Slaby <jirislaby@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>,
	Curtis Klein <curtis.klein@hpe.com>,
	wim@linux-watchdog.org
Cc: linux-watchdog@vger.kernel.org
Subject: was [Re: [PATCH v3] watchdog: Add hrtimer-based pretimeout feature]
Date: Sat, 4 Sep 2021 10:16:56 +0200	[thread overview]
Message-ID: <85ce6068-c98e-dbe0-a4b6-5c877b460f64@kernel.org> (raw)
In-Reply-To: <7fdd262e-84fb-0c34-baa9-162130f1e109@roeck-us.net>

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, but I don't know what the 
consequences are. The other possibility would be to pass wd_data 
directly to watchdog_hrtimer_pretimeout_stop.

I don't know how this can work on some machines (I verified it does).

--- 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

  reply	other threads:[~2021-09-04  8:17 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     ` Jiri Slaby [this message]
     [not found]       ` <54d77fb1-2531-c6ed-738e-9f661443b097@kernel.org>
2021-09-05 22:22         ` was [Re: [PATCH v3] watchdog: Add hrtimer-based pretimeout feature] Klein, Curtis
2021-09-05 22:56           ` Guenter Roeck

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