From: Peter Zijlstra <peterz@infradead.org>
To: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC/PATCH] No get_user/put_user while holding mmap_sem in do_pages_stat?
Date: Tue, 09 Dec 2008 17:35:46 +0100 [thread overview]
Message-ID: <1228840546.12654.2.camel@twins> (raw)
In-Reply-To: <493BDBE6.9040600@inria.fr>
On Sun, 2008-12-07 at 15:21 +0100, Brice Goglin wrote:
> Andrew Morton wrote:
> > Was lockdep able to tell you about this in any way?
> >
>
> With CONFIG_PROVE_LOCKING (assuming that it's enough), it doesn't detect
> the problem for real. It just says "possible recursive locking detected"
> between do_page_fault and sys_move_pages.
That is real - how much more real do you need a description of a
recursive deadlock to be?
> I actually understood the
> problem after hitting sysrq-t and always getting the following backtraces:
> * thread 1
> [<ffffffff80430cb8>] __down_write_nested+0x9c/0xb4
> [<ffffffff8028c2c4>] sys_mprotect+0xcc/0x230
> * thread 2
> [<ffffffff80430d73>] __down_read+0x9c/0xb4
> [<ffffffff80223f5c>] do_page_fault+0x551/0x9d9
> [...]
> [<ffffffff8043111a>] error_exit+0x0/0x70
> [<ffffffff802f5bec>] cap_task_movememory+0x0/0x3
> [<ffffffff8032b99d>] __put_user_4+0x1d/0x30
> [<ffffffff802a091f>] sys_move_pages+0x453/0x4c0
next prev parent reply other threads:[~2008-12-09 16:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-07 2:14 [RFC/PATCH] No get_user/put_user while holding mmap_sem in do_pages_stat? Brice Goglin
2008-12-07 2:50 ` Andrew Morton
2008-12-07 14:21 ` Brice Goglin
2008-12-09 14:19 ` Christoph Lameter
2008-12-09 16:35 ` Peter Zijlstra [this message]
2008-12-09 16:47 ` Brice Goglin
2008-12-09 17:46 ` Peter Zijlstra
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