From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755956Ab1FHWtu (ORCPT <rfc822;w@1wt.eu>);
	Wed, 8 Jun 2011 18:49:50 -0400
Received: from mail-qw0-f46.google.com ([209.85.216.46]:48956 "EHLO
	mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752090Ab1FHWtq (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 8 Jun 2011 18:49:46 -0400
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=date:from:to:cc:subject:message-id:references:mime-version
         :content-type:content-disposition:in-reply-to:user-agent;
        b=vtmMT4bbZs/QC/vaTlmcAoRGEHVLl13IS6MK6uGUreeXHuS6wJauBZEQ3wWuP7FjoS
         HzLbQRm+Rtg/EzZI+yJW0cfbfbFWHKt2PjD5mUJyjtH8YSXXk0ZAyPOsbFFVn2zMUxr2
         MYmnGdySrjnLKbbXZFZbBeB/dSyJKysXb4msc=
Date: Thu, 9 Jun 2011 00:49:41 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>, Len Brown <lenb@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Randy Dunlap <randy.dunlap@oracle.com>, Ingo Molnar <mingo@elte.hu>
Subject: Bug: ACPI, scheduling while atomic (was Re: [PATCH 0/4] sched: Make
 sleep inside atomic detection work on !PREEMPT)
Message-ID: <20110608224939.GC25771@somewhere.redhat.com>
References: <1307555315-30989-1-git-send-email-fweisbec@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1307555315-30989-1-git-send-email-fweisbec@gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Jun 08, 2011 at 07:48:31PM +0200, Frederic Weisbecker wrote:
> Aside it may mostly avoid the need for a specific PROVE_RCU
> check when we sleep inside an rcu read side critical section.
> 
> Better make sleeping inside atomic sections work everywhere.

BTW, it has led to detect a bug in the ACPI code. It happens in
!CONFIG_PREEMPT:

[    0.160187] BUG: scheduling while atomic: swapper/0/0x10000002
[    0.166016] no locks held by swapper/0.
[    0.170014] Modules linked in:
[    0.173107] Pid: 0, comm: swapper Not tainted 2.6.39+ #124
[    0.180014] Call Trace:
[    0.182481]  [<ffffffff81048685>] __schedule_bug+0x85/0x90
[    0.187967]  [<ffffffff817da98c>] schedule+0x75c/0xa40
[    0.190022]  [<ffffffff8109a1fd>] ? trace_hardirqs_on+0xd/0x10
[    0.200023]  [<ffffffff813879c0>] ? acpi_ps_free_op+0x22/0x24
[    0.205776]  [<ffffffff810554a5>] __cond_resched+0x25/0x40
[    0.210022]  [<ffffffff817daf3b>] _cond_resched+0x2b/0x40
[    0.215420]  [<ffffffff81386cbe>] acpi_ps_complete_op+0x262/0x278
[    0.220023]  [<ffffffff813874df>] acpi_ps_parse_loop+0x80b/0x960
[    0.230023]  [<ffffffff81386607>] acpi_ps_parse_aml+0x98/0x274
[    0.235859]  [<ffffffff81384cbb>] acpi_ns_one_complete_parse+0x103/0x120
[    0.240021]  [<ffffffff810886da>] ? up+0x2a/0x50
[    0.244641]  [<ffffffff81384cf3>] acpi_ns_parse_table+0x1b/0x34
[    0.250022]  [<ffffffff8138242a>] acpi_ns_load_table+0x4a/0x8c
[    0.260023]  [<ffffffff8138947c>] acpi_load_tables+0x9c/0x15d
[    0.265774]  [<ffffffff81d0b0f8>] acpi_early_init+0x6c/0xf7
[    0.270022]  [<ffffffff81cd8d31>] start_kernel+0x400/0x415
[    0.275508]  [<ffffffff81cd8346>] x86_64_start_reservations+0x131/0x135
[    0.280022]  [<ffffffff81cd844d>] x86_64_start_kernel+0x103/0x112

ACPI_PREEMPTION_POINT() is called from acpi_ps_complete_op() and schedules
if !PREEMPT. But preemption is disabled as we are in early bootup.