Stopping watchdog in watchdog driver remove functions

Stopping watchdog in watchdog driver remove functions

[Guenter Roeck]

Hi,

I noticed that several watchdog drivers stop the watchdog in trhe driver remove function.
A non-exhaustive list of drivers doing that is

	drivers/watchdog/bcm7038_wdt.c
	drivers/watchdog/cadence_wdt.c
	drivers/watchdog/imgpdc_wdt.c
	drivers/watchdog/jz4740_wdt.c
	drivers/watchdog/kempld_wdt.c
	drivers/watchdog/max77620_wdt.c
	drivers/watchdog/moxart_wdt.c
	drivers/watchdog/sama5d4_wdt.c
	drivers/watchdog/tangox_wdt.c
	drivers/watchdog/tegra_wdt.c

Since a watchdog has to be closed for its driver to be removable, one situation
where a watchdog is still running on unload is where the watchdog was opened but
not closed properly (eg by killing the watchdog application, or if the 'nowayout'
flag is set).

Given that, does it even make sense to stop the watchdog in the remove function ?
Should it even be permitted ?

Thanks,
Guenter

Re: Stopping watchdog in watchdog driver remove functions

[Wim Van Sebroeck]

Hi Guenter,

> I noticed that several watchdog drivers stop the watchdog in trhe driver 
> remove function.
> A non-exhaustive list of drivers doing that is
> 
> 	drivers/watchdog/bcm7038_wdt.c
> 	drivers/watchdog/cadence_wdt.c
> 	drivers/watchdog/imgpdc_wdt.c
> 	drivers/watchdog/jz4740_wdt.c
> 	drivers/watchdog/kempld_wdt.c
> 	drivers/watchdog/max77620_wdt.c
> 	drivers/watchdog/moxart_wdt.c
> 	drivers/watchdog/sama5d4_wdt.c
> 	drivers/watchdog/tangox_wdt.c
> 	drivers/watchdog/tegra_wdt.c
> 
> Since a watchdog has to be closed for its driver to be removable, one 
> situation
> where a watchdog is still running on unload is where the watchdog was 
> opened but
> not closed properly (eg by killing the watchdog application, or if the 
> 'nowayout'
> flag is set).
> 
> Given that, does it even make sense to stop the watchdog in the remove 
> function ?
> Should it even be permitted ?

>From an API point of view: if WDIOF_MAGICCLOSE is being used then the watchdog
_SHOULD_ continue to run when the watchdog was not properly closed (which
normally also results in a reboot of the system).
if WDIOF_MAGICCLOSE is not being used then closing the watchdog device means
that the driver needs to stop the watchdog.

Kind regards and happy new year to you all,
Wim.

Re: Stopping watchdog in watchdog driver remove functions

[Andy Shevchenko]

On Sun, Jan 1, 2017 at 1:14 PM, Wim Van Sebroeck <wim@iguana.be> wrote:

>> Given that, does it even make sense to stop the watchdog in the remove
>> function ?
>> Should it even be permitted ?
>
> From an API point of view: if WDIOF_MAGICCLOSE is being used then the watchdog
> _SHOULD_ continue to run when the watchdog was not properly closed (which
> normally also results in a reboot of the system).

Btw, some systems may require watchdog to be run in order to perform reboot.

-- 
With Best Regards,
Andy Shevchenko

Re: Stopping watchdog in watchdog driver remove functions

[Guenter Roeck]

On 01/01/2017 03:14 AM, Wim Van Sebroeck wrote:
> Hi Guenter,
>
>> I noticed that several watchdog drivers stop the watchdog in trhe driver
>> remove function.
>> A non-exhaustive list of drivers doing that is
>>
>> 	drivers/watchdog/bcm7038_wdt.c
>> 	drivers/watchdog/cadence_wdt.c
>> 	drivers/watchdog/imgpdc_wdt.c
>> 	drivers/watchdog/jz4740_wdt.c
>> 	drivers/watchdog/kempld_wdt.c
>> 	drivers/watchdog/max77620_wdt.c
>> 	drivers/watchdog/moxart_wdt.c
>> 	drivers/watchdog/sama5d4_wdt.c
>> 	drivers/watchdog/tangox_wdt.c
>> 	drivers/watchdog/tegra_wdt.c
>>
>> Since a watchdog has to be closed for its driver to be removable, one
>> situation
>> where a watchdog is still running on unload is where the watchdog was
>> opened but
>> not closed properly (eg by killing the watchdog application, or if the
>> 'nowayout'
>> flag is set).
>>
>> Given that, does it even make sense to stop the watchdog in the remove
>> function ?
>> Should it even be permitted ?
>
>>From an API point of view: if WDIOF_MAGICCLOSE is being used then the watchdog
> _SHOULD_ continue to run when the watchdog was not properly closed (which
> normally also results in a reboot of the system).
> if WDIOF_MAGICCLOSE is not being used then closing the watchdog device means
> that the driver needs to stop the watchdog.
>
All the above have WDIOF_MAGICCLOSE set. Does that mean they should not stop
the watchdog on remove ?

Happy new year everyone !

Guenter