linux-kernel - Re: [PATCH] THP: Use explicit memory barrier

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Message-ID: <5158DC7D.2040607@jp.fujitsu.com>
Date:	Mon, 01 Apr 2013 10:01:49 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] THP: Use explicit memory barrier

(2013/04/01 8:45), Minchan Kim wrote:
> __do_huge_pmd_anonymous_page depends on page_add_new_anon_rmap's
> spinlock for making sure that clear_huge_page write become visible
> after set set_pmd_at() write.
> 
> But lru_cache_add_lru uses pagevec so it could miss spinlock
> easily so above rule was broken so user may see inconsistent data.
> This patch fixes it with using explict barrier rather than depending
> on lru spinlock.
> 

Hmm...how about do_anonymous_page() ? there are no comments/locks/barriers.
Users can see non-zero value after page fault in theory ?

Thanks,
-Kame

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