From: Jan Kiszka <jan.kiszka@siemens.com>
To: Guenter Roeck <linux@roeck-us.net>,
Wim Van Sebroeck <wim@linux-watchdog.org>,
linux-watchdog@vger.kernel.org
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Tero Kristo <t-kristo@ti.com>
Subject: Re: [PATCH] watchdog: Respect handle_boot_enabled when setting last last_hw_keepalive
Date: Fri, 30 Jul 2021 23:37:27 +0200 [thread overview]
Message-ID: <def0c2e9-e035-7ffc-3216-27f461555ae5@siemens.com> (raw)
In-Reply-To: <211cd54b-29b4-e58a-341b-beffc05cfe85@roeck-us.net>
On 30.07.21 22:49, Guenter Roeck wrote:
> On 7/30/21 12:39 PM, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> We must not pet a running watchdog when handle_boot_enabled is off
>> because this requests to only start doing that via userspace, not during
>> probing.
>>
>
> The scope of the changed function is quite limited. See the
> definition of watchdog_set_last_hw_keepalive(). On top of that,
> __watchdog_ping() does a bit more than just ping the watchdog,
> and it only pings the watchdog in limited circumstances. On top of that,
> the scope of handle_boot_enabled is different: If enabled, it tells
> the watchdog core to keep pinging a watchdog until userspace opens
> the device. This is about continuous pings, not about an initial one.
> Given that, I'd rather have the watchdog subsystem issue an additional
> ping than risking a regression.
>
> The only driver calling watchdog_set_last_hw_keepalive() is rti_wdt.c.
> Does this patch solve a specific problem observed with that watchdog ?
Yes, it unbreaks support for handle_boot_enabled=no by not starting the
automatic pinging of the kernel until userspace opens the device.
Without this fix, the core will prematurely start kernel-side pinging,
and hanging userspace will never be detected.
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
next prev parent reply other threads:[~2021-07-30 21:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-30 19:39 [PATCH] watchdog: Respect handle_boot_enabled when setting last last_hw_keepalive Jan Kiszka
2021-07-30 20:49 ` Guenter Roeck
2021-07-30 21:37 ` Jan Kiszka [this message]
2021-07-30 22:39 ` Guenter Roeck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=def0c2e9-e035-7ffc-3216-27f461555ae5@siemens.com \
--to=jan.kiszka@siemens.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-watchdog@vger.kernel.org \
--cc=linux@roeck-us.net \
--cc=t-kristo@ti.com \
--cc=wim@linux-watchdog.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.