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Date: Thu, 13 Apr 2006 16:24:32 -0700
From: Andrew Morton <akpm@osdl.org>
To: Dave Peterson <dsp@llnl.gov>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, riel@surriel.com
Subject: Re: [PATCH 2/2] mm: fix mm_struct reference counting bugs in
 mm/oom_kill.c
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Dave Peterson <dsp@llnl.gov> wrote:
>
> The patch below fixes some mm_struct reference counting bugs in
> badness().

hm, OK, afaict the code _is_ racy.

But you're now calling mmput() inside read_lock(&tasklist_lock), and
mmput() can sleep in exit_aio() or in exit_mmap()->unmap_vmas().  So
sterner stuff will be needed.

I'll put a might_sleep() into mmput - it's a bit unexpected.