linux-kernel - Re: [PATCH] ANDROID: staging: add userpanic-dev driver

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Date:   Thu, 26 Aug 2021 12:54:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Woody Lin <woodylin@...gle.com>
Cc:     Todd Kjos <tkjos@...roid.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <christian@...uner.io>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev
Subject: Re: [PATCH] ANDROID: staging: add userpanic-dev driver

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
> <gregkh@...uxfoundation.org> 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 <woodylin@...gle.com>
> > > ---
> > >  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?

thanks,

greg k-h