linux-kernel - Re: boot failure, "DWARF2 unwinder stuck at 0xc0100199"

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Message-Id: <20060821094718.79c9a31a.rdunlap@xenotime.net>
Date:	Mon, 21 Aug 2006 09:47:18 -0700
From:	"Randy.Dunlap" <rdunlap@...otime.net>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	"Andi Kleen" <ak@...e.de>, <linux-kernel@...r.kernel.org>
Subject: Re: boot failure, "DWARF2 unwinder stuck at 0xc0100199"

On Mon, 21 Aug 2006 08:48:19 +0200 Jan Beulich wrote:

> >>> "J. Bruce Fields" <bfields@...ldses.org> 20.08.06 03:31 >>>
> >As of 2.6.18-rc3, one of my test machines stopped booting.  I'm not
> >seeing the whole OOPS (I could probably set up a serial console if
> >necessary), but it ends in something like:
> >
> >trace_hardirqs_on
> >idesci_pc_intr
> >ide_intr
> >handle_IRQ_event
> >__do_IRQ
> >do_IRQ
> >common_interrupt
> >default_idle
> >apm_cpu_idle
> >cpu_idle
> >rest_init
> >start_kernel
> >0xc0100199
> >DWARF2 unwinder stuck at 0xc0100199
> >Leftover inexact backtrace:
> > =======================
> > BUG: unable to handle kernel paging request at virtual address 0000b034
> > printing eip:
> >c0103712
> >*pde = 00000000
> >Recursive die() failure, output suppressed
> > <0>Kernel panic - not syncing: Fatal exception in interrupt
> >
> >Bisecting, it looks like this starts happening after c97d20a...,
> >"[PATCH] i386: Do backtrace fallback too", though it's a little tricky
> >since the compile is broken near there for a little while.
> >
> >Kernel config appended; let me know if anything else would be useful.
> 
> The 'stuck' unwinder issue at hand already has a fix, though planned to
> be merged for 2.6.19 only. The crash after switching to the legacy
> stack trace code is bad, though, but has little to do with the unwinder
> additions/changes. The way that code reads the stack is just
> inappropriate in contexts where things must be expected to be broken.

"merged for 2.6.19" meaning:
- in (before) 2.6.19, or
- after 2.6.19 is released

If "after," then it will likely need to be added to -stable also,
so it might as well go in "before" 2.6.19 is released.

> Finally, there is no visible correlation between the original problem (in
> or from trace_hardirqs_on) and the unwinder - once that problem is
> fixed, you're not likely to see the recursive die failure anymore either.

---
~Randy
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