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Re: [PATCH 03/16] mm: check rb_subtree_gap correctness

To: Sasha Levin <levinsasha928@gmail.com>
Subject: Re: [PATCH 03/16] mm: check rb_subtree_gap correctness
From: Michel Lespinasse <walken@google.com>
Date: Mon, 12 Nov 2012 03:55:16 -0800
Cc: Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org, Russell King <linux@arm.linux.org.uk>, Ralf Baechle <ralf@linux-mips.org>, Paul Mundt <lethal@linux-sh.org>, "David S. Miller" <davem@davemloft.net>, Chris Metcalf <cmetcalf@tilera.com>, x86@kernel.org, William Irwin <wli@holomorphy.com>, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, Dave Jones <davej@redhat.com>
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On Fri, Nov 9, 2012 at 6:13 AM, Sasha Levin <levinsasha928@gmail.com> wrote:
> While fuzzing with trinity inside a KVM tools (lkvm) guest, using today's 
> -next
> kernel, I'm getting these:
>
> [  117.007714] free gap 7fba0dd1c000, correct 7fba0dcfb000
> [  117.019773] map_count 750 rb -1
> [  117.028362] ------------[ cut here ]------------
> [  117.029813] kernel BUG at mm/mmap.c:439!
>
> Note that they are very easy to reproduce.

Thanks for the report. I had trouble reproducing this on Friday, but
after Hugh came up with an easy test case I think I have it figured
out. I sent out a proposed fix as "[PATCH 0/3] fix missing
rb_subtree_gap updates on vma insert/erase". Let's follow up the
discussion there if necessary.

Cheers,

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.

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