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Date: Sat, 6 Jul 2013 10:02:27 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Dave Jones <davej@redhat.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: scheduling while atomic & hang.
Message-ID: <20130706080225.GA439@somewhere>
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On Fri, Jul 05, 2013 at 12:27:51PM -0700, Linus Torvalds wrote:
> On Thu, Jul 4, 2013 at 11:51 PM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > It would be nice to have a full-kernel-stack backtrace printout as an
> > option, which prints entries 'above' the current RSP.
> 
> One problem with that is that it is likely to be mostly overwritten by
> the debug code that is about to print this all out - and any non-debug
> code may well be really old, just with a sufficiently deep stack trace
> to show up. Not to mention missing any irq-stack changes etc anyway.
> 
> So it can easily be *very* misleading - I'm not sure how useful it
> would be as an idea.
> 
>                 Linus

So if the unwider doesn't run with the same stak than the target,
it migh work. This can work with BUG for example But I believe that WARN
doesn't do a trap in x86.