linux-kernel - Re: [PATCH v8 0/3] watchdog: allow setting deadline for opening /dev/watchdogN

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Message-ID: <87pnsw3bm9.fsf@haabendal.dk>
Date:   Wed, 16 Jan 2019 15:45:02 +0100
From:   Esben Haabendal <esben@...bendal.dk>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Cc:     "linux-watchdog\@vger.kernel.org" <linux-watchdog@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Jonathan Corbet <corbet@....net>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc\@vger.kernel.org" <linux-doc@...r.kernel.org>,
        "martin\@hundeboll.net" <martin@...deboll.net>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
Subject: Re: [PATCH v8 0/3] watchdog: allow setting deadline for opening /dev/watchdogN

Rasmus Villemoes <rasmus.villemoes@...vas.dk> writes:

> If a watchdog driver tells the framework that the device is running,
> the framework takes care of feeding the watchdog until userspace opens
> the device. If the userspace application which is supposed to do that
> never comes up properly, the watchdog is fed indefinitely by the
> kernel. This can be especially problematic for embedded devices.
>
> The existing handle_boot_enabled cmdline parameter/config option
> partially solves that, but that is only usable for the subset of
> hardware watchdogs that have (or can be configured by the bootloader
> to have) a timeout that is sufficient to make it realistic for
> userspace to come up. Many devices have timeouts of only a few
> seconds, or even less, making handle_boot_enabled insufficient.
>
> These patches allow one to set a maximum time for which the kernel
> will feed the watchdog, thus ensuring that either userspace has come
> up, or the board gets reset. This allows fallback logic in the
> bootloader to attempt some recovery (for example, if an automatic
> update is in progress, it could roll back to the previous version).
>
> The patches have been tested on a Raspberry Pi 2 and a Wandboard.
>
> Changes in v8: Redo on top of 5.0-rc1 - in particular, adapt to the
> jiffies->ktime_t conversion (1ff68820 "watchdog: core: make sure the
> watchdog_worker is not deferred"). Add a patch to make the hardware
> timeout at the deadline as requested by Guenther - which was actually
> made very easy by the ktime_t conversion.
>
> v7 submission at <https://lore.kernel.org/lkml/1511865350-20665-1-git-send-email-rasmus.villemoes@prevas.dk/>
>
> Rasmus Villemoes (3):
>   watchdog: introduce watchdog.open_timeout commandline parameter
>   watchdog: introduce CONFIG_WATCHDOG_OPEN_TIMEOUT
>   watchdog: make the device time out at open_deadline when open_timeout
>     is used
>
>  .../watchdog/watchdog-parameters.txt          |  9 ++++
>  drivers/watchdog/Kconfig                      |  9 ++++
>  drivers/watchdog/watchdog_dev.c               | 42 +++++++++++++++----
>  3 files changed, 53 insertions(+), 7 deletions(-)

For the whole series:
Acked-by: Esben Haabendal <esben@...bendal.dk>