All of lore.kernel.org
 help / color / mirror / Atom feed
From: Heinrich Schuchardt <xypron.glpk@gmx.de>
To: u-boot@lists.denx.de
Subject: [PATCH 2/2] watchdog: add watchdog behavior configuration
Date: Wed, 23 Sep 2020 19:31:00 +0200	[thread overview]
Message-ID: <8070fb73-d42b-fa66-98a6-a2b9926b2d3f@gmx.de> (raw)
In-Reply-To: <20200923171409.GT14816@bill-the-cat>

On 9/23/20 7:14 PM, Tom Rini wrote:
> On Wed, Sep 23, 2020 at 07:01:54PM +0200, Mark Kettenis wrote:
>>> From: Michael Walle <michael@walle.cc>
>>> Date: Wed, 23 Sep 2020 18:45:27 +0200
>>>
>>> Let the user choose between three different behaviours of the watchdog:
>>>  (1) Keep the watchdog disabled
>>>  (2) Supervise u-boot
>>>  (3) Supervise u-boot and the operating systen (default)
>>>
>>> Option (2) will disable the watchdog right before handing control to the
>>> operating system. This is useful when the OS is not aware of the
>>> watchdog. Option (3) doesn't disable the watchdog and assumes the OS
>>> will continue servicing.
>>
>> (3) can't be the default, at least for EFI
>>
>> The UEFI standard explicitly says that upon calling
>> ExitBootServices(), the watchdog timer is disabled.
>>
>> In general, you can't expect an OS to have support for a particular
>> watchdog timer.  So (3) only makes sense in cases where U-Boot is
>> bundled with an OS image.
>
> We need to be careful here then.  The current and historical / generally
> expected behavior is if we've enabled the watchdog we supervise it and
> leave it enabled for the OS.  Given what UEFI requires I'd like to see
> that case handled with a print about disabling the watchdog so it's not

Not printf(), maybe log_info().

The disabling has to occur in ExitBootServices() (aka.
efi_exit_boot_services()). Here we are in the middle of an executing
UEFI application. Printing anything on the screen may mess up the output
of the UEFI application.

So, please, don't output anything.

Best regards

Heinrich

> a surprise to the user.  I say this because it's a surprise to me and I
> guess answers the question of "how does x86 handle this?" I had the
> other day.
>

  reply	other threads:[~2020-09-23 17:31 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-23 16:45 [PATCH 1/2] watchdog: Hide WATCHDOG_RESET_DISABLE Michael Walle
2020-09-23 16:45 ` [PATCH 2/2] watchdog: add watchdog behavior configuration Michael Walle
2020-09-23 17:01   ` Mark Kettenis
2020-09-23 17:14     ` Tom Rini
2020-09-23 17:31       ` Heinrich Schuchardt [this message]
2020-09-23 17:35         ` Tom Rini
2020-09-24  7:33           ` Michael Walle
2020-09-24  8:10             ` Mark Kettenis
2020-09-24  8:20               ` Michael Walle
2020-09-24 10:22                 ` Mark Kettenis
2020-09-24 21:05                   ` Michael Walle
2020-09-24 13:19             ` Tom Rini
2020-09-24 20:30               ` Michael Walle
2020-09-24 20:58                 ` Mark Kettenis
2020-09-24 21:14                   ` Michael Walle
2020-09-25  1:17                     ` Tom Rini
2020-09-25  8:36               ` Wolfgang Denk
2020-09-25 11:29                 ` Heinrich Schuchardt
2020-09-25 13:00                   ` Tom Rini
2020-09-25 13:26                     ` Heinrich Schuchardt
2020-09-26  8:45                       ` Wolfgang Denk
2020-09-26 10:54                         ` Mark Kettenis
2020-09-26 12:39                           ` Heinrich Schuchardt
2020-09-26 12:44                             ` Tom Rini
2020-09-27 16:06                               ` Michael Walle
2020-09-28 15:34                                 ` Tom Rini
2020-09-26 14:40                             ` Wolfgang Denk
2020-09-26 14:22                           ` Wolfgang Denk
2020-09-25 13:04                   ` Wolfgang Denk
2020-10-04 14:55                     ` Michael Walle
2020-10-04 15:10                       ` Heinrich Schuchardt
2020-10-04 15:40                         ` Tom Rini
2020-09-23 17:53       ` Mark Kettenis
2020-09-23 18:51         ` Heinrich Schuchardt
2020-09-23 19:02           ` Tom Rini
2020-09-23 20:01             ` Heinrich Schuchardt
2020-09-23 20:23               ` Tom Rini
2020-09-23 20:58                 ` Heinrich Schuchardt
2020-09-23 21:09                   ` Tom Rini
2020-09-23 20:38           ` Michael Walle
2020-09-23 21:01             ` Heinrich Schuchardt
2020-09-23 17:21   ` Heinrich Schuchardt
2020-09-23 17:28     ` Tom Rini
2020-09-24  6:53       ` Michael Walle

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=8070fb73-d42b-fa66-98a6-a2b9926b2d3f@gmx.de \
    --to=xypron.glpk@gmx.de \
    --cc=u-boot@lists.denx.de \
    /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.