linux-kernel - Re: [PATCH] watchdog: only print critical log when the watchdog fails to be stopped

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Message-ID: <b84d6b59-1829-4d93-8720-75d1b24ce7d1@roeck-us.net>
Date: Mon, 27 Jan 2025 06:29:46 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: "liuchao (CR)" <liuchao173@...wei.com>,
 "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>
Cc: caihe <caihe@...wei.com>, lixiaokeng <lixiaokeng@...wei.com>
Subject: Re: [PATCH] watchdog: only print critical log when the watchdog fails
 to be stopped

On 1/27/25 01:35, liuchao (CR) wrote:
> On 1/26/25 21:10, Guenter Roeck wrote:
>> On 1/26/25 00:38, Liu Chao wrote:
>>> Every time the user echoes 0 > /dev/watchdog0, meaningless critical
>>> log is printed.
>>>
>>
>> It is not meaningless, and it will still be displayed after this change, making the
>> change pointless.
> 
> The change is not pointless. For example, the softdog driver does not invoke
> watchdog_stop or print logs in the watchdog_release.
> 

It seems to me that is a problem in the softdog driver.

The change is actually worse than I initially thought.
The message is _supposed_ to be displayed if watchdog_stop()
is not called while the watchdog is running (i.e., if err == -EBUSY).
Otherwise it would not be displayed for real hardware watchdogs
which are not stopped because they were running and watchdog_stop()
is not called because WDIOF_MAGICCLOSE is set in the driver and the
magic release byte was not written.

Specifically, the softdog driver has WDIOF_MAGICCLOSE set. It is not
supposed to be unloadable (or unloaded) while the watchdog is running.

Guenter