From mboxrd@z Thu Jan  1 00:00:00 1970
From: dann frazier <dannf@debian.org>
Date: Tue, 20 Jul 2010 17:35:12 +0000
Subject: ia64 hang/mca running gdb 'make check'
Message-Id: <20100720173512.GF26783@ldl.fc.hp.com>
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To: linux-ia64@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Hugh Dickins <hugh.dickins@tiscali.co.uk>, Rik van Riel <riel@redhat.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Nick Piggin <npiggin@suse.de>, Mel Gorman <mel@csn.ul.ie>, Minchan Kim <minchan.kim@gmail.com>, Ralf Baechle <ralf@linux-mips.org>

Debian's ia64 autobuilders have been experiencing system crashes while
trying to run the gdb test suite:
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bugX8574

I was able to reproduce this w/ the latest git tree, and bisected it
down to this commit, introduced in 2.6.32:

  commit 62eede62dafb4a6633eae7ffbeb34c60dba5e7b1
  Author: Hugh Dickins <hugh.dickins@tiscali.co.uk>
  Date:   Mon Sep 21 17:03:34 2009 -0700

    mm: ZERO_PAGE without PTE_SPECIAL

    Reinstate anonymous use of ZERO_PAGE to all architectures, not just to
    those which __HAVE_ARCH_PTE_SPECIAL: as suggested by Nick Piggin.

    Contrary to how I'd imagined it, there's nothing ugly about this, just a
    zero_pfn test built into one or another block of vm_normal_page().

    But the MIPS ZERO_PAGE-of-many-colours case demands is_zero_pfn() and
    my_zero_pfn() inlines.  Reinstate its mremap move_pte() shuffling of
    ZERO_PAGEs we did from 2.6.17 to 2.6.19?  Not unless someone shouts for
    that: it would have to take vm_flags to weed out some cases.

fyi, I found this to not be reproducible on SLES11 SP1 (which is
2.6.32-based). I compared the .configs and found that the relevant
difference is the PAGE_SIZE. It does not fail w/ 64KB pages, but
reliably fails w/ 16KB pages.