linux-kernel - Re: [PATCH 5/5] Always print panic message on current console

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Message-ID: <20091012113055.13d3b7e3@jbarnes-g45>
Date:	Mon, 12 Oct 2009 11:30:55 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Bernhard Walle <bernhard@...lle.de>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...uxfoundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] Always print panic message on current console

On Mon, 12 Oct 2009 20:24:56 +0200
Bernhard Walle <bernhard@...lle.de> wrote:

> Andi Kleen schrieb:
> > Bernhard Walle <bernhard@...lle.de> writes:
> > 
> >> The kernel offers with TIOCL_GETKMSGREDIRECT ioctl() the
> >> possibility to redirect the kernel messages to a specific console.
> >>
> >> However, since it's not possible to switch to the kernel message
> >> console after a panic(), it would be nice if the kernel would
> >> print the panic message on the current console.
> > 
> > The basic idea is good, but you really need to call this in a lot
> > more places, which print some addition needed information before
> > the panic. The one liner panic is often not enough to decide what
> > went wrong. Example are machine checks, oopses, probably more.
> > 
> > In general for the recent work to switch the video mode on panic
> > we need a generalized hook for this anyways, so you could use
> > some generalized function.
> 
> Is that video switch called in a panic notifier list or does that
> introduce a new hook?
> 
> One problem is that kexec is executed before the panic notifier. Which
> is okay for printk(), but it would be very good if the video switch
> would occur before kexec.

It's called in the panic notifier atm.  Yeah sounds like kexec vs
notifiers should be reordered a bit (or the current panic notifier
should be split into notify and "yes we actually failed to do anything"
cases).

-- 
Jesse Barnes, Intel Open Source Technology Center
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