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From: Woody Lin <firstname.lastname@example.org>
To: Greg Kroah-Hartman <email@example.com>
Cc: "Todd Kjos" <firstname.lastname@example.org>,
"Arve Hjønnevåg" <email@example.com>,
"Martijn Coenen" <firstname.lastname@example.org>,
"Joel Fernandes" <email@example.com>,
"Christian Brauner" <firstname.lastname@example.org>,
"Hridya Valsaraju" <email@example.com>,
"Suren Baghdasaryan" <firstname.lastname@example.org>,
Subject: Re: [PATCH] ANDROID: staging: add userpanic-dev driver
Date: Fri, 27 Aug 2021 11:51:03 +0800 [thread overview]
Message-ID: <CAHn4Dee0d+cdSmMCB4YVMp-9swo=0UQ5gm4kz43RVY11KFnM1w@mail.gmail.com> (raw)
On Thu, Aug 26, 2021 at 6:54 PM Greg Kroah-Hartman
> On Thu, Aug 26, 2021 at 06:23:53PM +0800, Woody Lin wrote:
> > On Thu, Aug 26, 2021 at 5:48 PM Greg Kroah-Hartman
> > <email@example.com> wrote:
> > >
> > > On Thu, Aug 26, 2021 at 05:28:54PM +0800, Woody Lin wrote:
> > > > Add char device driver 'userpanic-dev' that exposes an interface to
> > > > userspace processes to request a system panic with customized panic
> > > > message.
> > > >
> > > > Signed-off-by: Woody Lin <firstname.lastname@example.org>
> > > > ---
> > > > drivers/staging/android/Kconfig | 12 +++
> > > > drivers/staging/android/Makefile | 1 +
> > > > drivers/staging/android/userpanic-dev.c | 110 ++++++++++++++++++++++++
> > >
> > > Why is this in staging? What is wrong with it that it can not just go
> > > into the real part of the kernel? A TODO file is needed explaining what
> > > needs to be done here in order for it to be accepted.
> > Got it. No more TODO for this driver and I will move it to drivers/android/.
> > >
> > > But why is this really needed at all? Why would userspace want to panic
> > > the kernel in yet-another-way?
> > The idea is to panic the kernel with a panic message specified by the userspace
> > process requesting the panic. Without this the panic handler can only collect
> > panic message "sysrq triggered crash" for a panic triggered by user processes.
> > Using this driver, user processes can put an informative description -
> > process name,
> > reason ...etc. - to the panic message.
> What custom userspace tool is going to use this new user/kernel api and
> again, why is it needed? Who needs to panic the kernel with a custom
> message and where is that used?
It's for Android's services. Currently there are usages like these:
* init requests panic in InitFatalReboot (abort handler).
* llkd requests panic to recover kernel live-lock.
* Watchdog requests panic to recover timeout-loop.
So to improve the panic message from "sysrq triggered crash" to a more
informative one (e.g.: "Watchdog break timeout-loop", "llkd panic
live-lock"), we'd like to add this driver to expose a dedicated
interface for userspace to panic the kernel with a custom message. Later
the panic handler implemented per platform can collect the message and
use it to build the crash report. A crash report with a more readable
title (compared to the generic "sysrq triggered crash") will be easier
to categorize, triage, etc.
And the reason to submit this to upstream, instead of making it a vendor
module, is that we'd like to enable it for the early stage of "init", where
none of the kernel module has been mounted.
> greg k-h
next prev parent reply other threads:[~2021-08-27 3:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-26 9:28 Woody Lin
2021-08-26 9:48 ` Greg Kroah-Hartman
2021-08-26 10:23 ` Woody Lin
2021-08-26 10:54 ` Greg Kroah-Hartman
2021-08-27 3:51 ` Woody Lin [this message]
2021-08-27 7:14 ` Greg Kroah-Hartman
2021-09-01 8:56 ` Woody Lin
2021-08-26 10:01 ` Greg Kroah-Hartman
2021-08-26 13:06 ` kernel test robot
2021-08-26 13:57 ` kernel test robot
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