linux-kernel - Re: [PATCH 13/12] ksm: fix munlock during exit

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Message-ID: <20090826202843.GC14722@random.random>
Date:	Wed, 26 Aug 2009 22:28:43 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Hugh Dickins <hugh.dickins@...cali.co.uk>
Cc:	Izik Eidus <ieidus@...hat.com>, Rik van Riel <riel@...hat.com>,
	Chris Wright <chrisw@...hat.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Justin M. Forbes" <jmforbes@...uxtx.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 13/12] ksm: fix munlock during exit_mmap deadlock

On Wed, Aug 26, 2009 at 08:57:27PM +0100, Hugh Dickins wrote:
> that might be useful.  But KSM_RUN_UNMERGE wouldn't be able to use_mm
> since it's coming from a normal user process - perhaps it should be a
> kill-me-first like swapoff via PF_SWAPOFF.

That would sound just perfect if only there wasn't also a break_cow in
the kksmd context that will trigger page allocation as it can't
takeover the KSM page like it would normally be guaranteed to do for a
cow on a regular anon page mapped readonly in the pte after read
swapin for example. Still for the echo 2 kill me first definitely
makes sense, so maybe we should differentiate the two cases (kksmd and
sysfs).
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