linux-kernel - Re: Lockless/Get_User_Pages_Fast causes Xorg 1.4.99.* to lock

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Message-ID: <4871330A.3030400@acm.org>
Date:	Sun, 06 Jul 2008 15:03:06 -0600
From:	Zan Lynx <zlynx@....org>
To:	Hugh Dickins <hugh@...itas.com>
CC:	Ryan Hope <rmh3093@...il.com>, LKML <linux-kernel@...r.kernel.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Lockless/Get_User_Pages_Fast causes Xorg 1.4.99.* to lock

Hugh Dickins wrote:
> On Fri, 4 Jul 2008, Zan Lynx wrote:
[cut]
> Useful info, thank you; even more useful was the Code line in your attachment
> 
>> [  269.224557] Code: 00 00 48 b9 00 00 00 00 00 e2 ff ff 48 21 d8 48 c1 e8 0c 48 8d 14 c5 00 00 00 00 48 c1 e0 06 48 29 d0 48 01 c1 0f 84 10 ff ff ff <48> 8b 01 48 89 ca f6 c4 40 74 04 48 8b 51 10 90 ff 42 08 90 ff 
> 
> which is enough to identify the oops as in copy_one_pte's get_page(page).
> Here's a patch I think we need, which I'm hoping will fix both your
> crashes - please let us know - thanks a lot.
> 
> Stop mprotect's pte_modify from wiping out the x86 pte_special bit, which
> caused oops thereafter when vm_normal_page thought X's abnormal was normal.
[cut patch]

I can report that this fixes things for me as well.  Thank you.
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