linux-kernel - Re: [PATCH] THP: fix comment about memory barrier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <515E9DC5.4050402@jp.fujitsu.com>
Date:	Fri, 05 Apr 2013 18:47:49 +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>, Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] THP: fix comment about memory barrier

(2013/04/05 17:16), Minchan Kim wrote:
> Now, memory barrier in __do_huge_pmd_anonymous_page doesn't work.
> Because lru_cache_add_lru uses pagevec so it could miss spinlock
> easily so above rule was broken so user might see inconsistent data.
> 
> I was not first person who pointed out the problem. Mel and Peter
> pointed out a few months ago and Peter pointed out further that
> even spin_lock/unlock can't make sure it.
> http://marc.info/?t=134333512700004
> 
> 	In particular:
> 
>          	*A = a;
>          	LOCK
>          	UNLOCK
>          	*B = b;
> 
> 	may occur as:
> 
>          	LOCK, STORE *B, STORE *A, UNLOCK
> 
> At last, Hugh pointed out that even we don't need memory barrier
> in there because __SetPageUpdate already have done it from
> Nick's [1] explicitly.
> 
> So this patch fixes comment on THP and adds same comment for
> do_anonymous_page, too because everybody except Hugh was missing
> that. It means we needs COMMENT about that.
> 
> [1] 0ed361dec "mm: fix PageUptodate data race"
> 
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Acked-by: Andrea Arcangeli <aarcange@...hat.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/