Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S934246Ab2JYAIQ (ORCPT <rfc822;w@1wt.eu>);
	Wed, 24 Oct 2012 20:08:16 -0400
Received: from mail-da0-f46.google.com ([209.85.210.46]:53698 "EHLO
	mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932178Ab2JYAIO (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 24 Oct 2012 20:08:14 -0400
Date: Wed, 24 Oct 2012 17:08:11 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
X-X-Sender: rientjes@chino.kir.corp.google.com
To: Sasha Levin <levinsasha928@gmail.com>, Mel Gorman <mgorman@suse.de>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Rik van Riel <riel@redhat.com>
cc: Dave Jones <davej@redhat.com>, Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>, bhutchings@solarflare.com,
        Konstantin Khlebnikov <khlebnikov@openvz.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Hugh Dickins <hughd@google.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in
 numa_maps
In-Reply-To: <CA+1xoqd6MEFP-eWdnWOrcz2EmE6tpd7UhgJyS8HjQ8qrGaMMMw@mail.gmail.com>
Message-ID: <alpine.DEB.2.00.1210241659260.22819@chino.kir.corp.google.com>
References: <20121008150949.GA15130@redhat.com> <CAHGf_=pr1AYeWZhaC2MKN-XjiWB7=hs92V0sH-zVw3i00X-e=A@mail.gmail.com> <alpine.DEB.2.00.1210152055150.5400@chino.kir.corp.google.com> <CAHGf_=rLjQbtWQLDcbsaq5=zcZgjdveaOVdGtBgBwZFt78py4Q@mail.gmail.com>
 <alpine.DEB.2.00.1210152306320.9480@chino.kir.corp.google.com> <CAHGf_=pemT6rcbu=dBVSJE7GuGWwVFP+Wn-mwkcsZ_gBGfaOsg@mail.gmail.com> <alpine.DEB.2.00.1210161657220.14014@chino.kir.corp.google.com> <alpine.DEB.2.00.1210161714110.17278@chino.kir.corp.google.com>
 <20121017040515.GA13505@redhat.com> <alpine.DEB.2.00.1210162222100.26279@chino.kir.corp.google.com> <CA+1xoqe74R6DX8Yx2dsp1MkaWkC1u6yAEd8eWEdiwi88pYdPaw@mail.gmail.com> <alpine.DEB.2.00.1210241633290.22819@chino.kir.corp.google.com>
 <CA+1xoqd6MEFP-eWdnWOrcz2EmE6tpd7UhgJyS8HjQ8qrGaMMMw@mail.gmail.com>
User-Agent: Alpine 2.00 (DEB 1167 2008-08-23)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 3075
Lines: 60

On Wed, 24 Oct 2012, Sasha Levin wrote:

> > This should be fixed by 9e7814404b77 ("hold task->mempolicy while
> > numa_maps scans.") in 3.7-rc2, can you reproduce any issues reading
> > /proc/pid/numa_maps on that kernel?
> 
> I was actually referring to the warnings Dave Jones saw when fuzzing
> with trinity after the
> original patch was applied.
> 
> I still see the following when fuzzing:
> 
> [  338.467156] BUG: sleeping function called from invalid context at
> kernel/mutex.c:269
> [  338.473719] in_atomic(): 1, irqs_disabled(): 0, pid: 6361, name: trinity-main
> [  338.481199] 2 locks held by trinity-main/6361:
> [  338.486629]  #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff810aa314>]
> __do_page_fault+0x1e4/0x4f0
> [  338.498783]  #1:  (&(&mm->page_table_lock)->rlock){+.+...}, at:
> [<ffffffff8122f017>] handle_pte_fault+0x3f7/0x6a0
> [  338.511409] Pid: 6361, comm: trinity-main Tainted: G        W
> 3.7.0-rc2-next-20121024-sasha-00001-gd95ef01-dirty #74
> [  338.530318] Call Trace:
> [  338.534088]  [<ffffffff8114e393>] __might_sleep+0x1c3/0x1e0
> [  338.539358]  [<ffffffff83ae5209>] mutex_lock_nested+0x29/0x50
> [  338.545253]  [<ffffffff8124fc3e>] mpol_shared_policy_lookup+0x2e/0x90
> [  338.545258]  [<ffffffff81219ebe>] shmem_get_policy+0x2e/0x30
> [  338.545264]  [<ffffffff8124e99a>] get_vma_policy+0x5a/0xa0
> [  338.545267]  [<ffffffff8124fce1>] mpol_misplaced+0x41/0x1d0
> [  338.545272]  [<ffffffff8122f085>] handle_pte_fault+0x465/0x6a0
> [  338.545278]  [<ffffffff81131e04>] ? __rcu_read_unlock+0x44/0xb0
> [  338.545282]  [<ffffffff81230baa>] handle_mm_fault+0x32a/0x360
> [  338.545286]  [<ffffffff810aa5b0>] __do_page_fault+0x480/0x4f0
> [  338.545293]  [<ffffffff8111a706>] ? del_timer+0x26/0x80
> [  338.545298]  [<ffffffff811c7313>] ? rcu_cleanup_after_idle+0x23/0x170
> [  338.545302]  [<ffffffff811ca9a4>] ? rcu_eqs_exit_common+0x64/0x3a0
> [  338.545305]  [<ffffffff811c8c66>] ? rcu_eqs_enter_common+0x7c6/0x970
> [  338.545309]  [<ffffffff811cafdc>] ? rcu_eqs_exit+0x9c/0xb0
> [  338.545312]  [<ffffffff810aa666>] do_page_fault+0x26/0x40
> [  338.545317]  [<ffffffff810a3a40>] do_async_page_fault+0x30/0xa0
> [  338.545321]  [<ffffffff83ae9268>] async_page_fault+0x28/0x30
> 

Ok, this looks the same but it's actually a different issue: 
mpol_misplaced(), which now only exists in linux-next and not in 3.7-rc2, 
calls get_vma_policy() which may take the shared policy mutex.  This 
happens while holding page_table_lock from do_huge_pmd_numa_page() but 
also from do_numa_page() while holding a spinlock on the ptl, which is 
coming from the sched/numa branch.

Is there anyway that we can avoid changing the shared policy mutex back 
into a spinlock (it was converted in b22d127a39dd ["mempolicy: fix a race 
in shared_policy_replace()"])?

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