Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754733Ab2FSTrf (ORCPT ); Tue, 19 Jun 2012 15:47:35 -0400 Received: from am1ehsobe005.messaging.microsoft.com ([213.199.154.208]:45976 "EHLO am1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753482Ab2FSTre (ORCPT ); Tue, 19 Jun 2012 15:47:34 -0400 X-Forefront-Antispam-Report: CIP:160.33.194.230;KIP:(null);UIP:(null);IPV:NLI;H:usculsndmail03v.am.sony.com;RD:mail03.sonyusa.com;EFVD:NLI X-SpamScore: -3 X-BigFish: VPS-3(zzbb2dI98dI1432Izz1202hzz8275bhz2fh2a8h668h839hd25hf0ah) Message-ID: <4FE0D70F.2000607@am.sony.com> Date: Tue, 19 Jun 2012 12:46:23 -0700 From: Frank Rowand Reply-To: User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: Aaditya Kumar , CC: Thomas Gleixner , "linux-kernel@vger.kernel.org" , "rostedt@goodmis.org" , "mingo@kernel.org" , "C.Emde@osadl.org" , "jkacur@redhat.com" , "Rowand, Frank" , "Bird, Tim" , "Ohara, Takuzo" , "Iibuchi, Kan (TDG)" Subject: Re: [RFC][RT][PATCH] mm: Do not use stop_machine() for __zone_pcp_udpate() for CONFIG_PREEMPT_RT_FULL References: In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-OriginatorOrg: am.sony.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2843 Lines: 79 Adding to the distribution list: the author of the patch that included the call to stop_machine() (commit 112067f0905b2de862c607ee62411cf47d2fe5c4). On 06/19/12 11:32, Aaditya Kumar wrote: > The code path of __zone_pcp_update() has following locks, which in > CONFIG_PREEMPT_RT_FULL=y are rt-mutex. > - pa_lock locked by cpu_lock_irqsave() > - zone->lock locked by free_pcppages_bulk() > > Since __zone_pcp_update() is called from stop_machine(), so with > CONFIG_PREEMPT_RT_FULL=y > we get following backtrace when __zone_pcp_update() is called during > memory hot plugging while > doing heavy file I/O. > > I think stop_machine() may not be required for calling __zone_pcp_update() > in case of CONFIG_PREEMPT_RT_FULL=y as acquiring pa_lock in __zone_pcp_update() > should be sufficient to isolate pcp pages and to setup per cpu pagesets. > > Can someone please let me know if am missing anything here? > > > The backtrace that this patch fixes: > BUG: scheduling while atomic: migration/0/7/0x00000002 > Modules linked in: v2p > Backtrace: > [<800111a0>] (dump_backtrace+0x0/0x10c) from [<802d7b7c>] > (dump_stack+0x18/0x1c) > r6:80c8fc28 r5:80c8f9a0 r4:00000000 r3:60000013 > [<802d7b64>] (dump_stack+0x0/0x1c) from [<8001e81c>] (__schedule_bug+0x64/0x74) > [<8001e7b8>] (__schedule_bug+0x0/0x74) from [<802d7fa0>] > (__schedule+0x68/0x604) > r4:8051bf00 r3:00000000 > [<802d7f38>] (__schedule+0x0/0x604) from [<802d8a78>] (schedule+0x98/0xbc) > [<802d89e0>] (schedule+0x0/0xbc) from [<802d9e14>] > (rt_spin_lock_slowlock+0x168/0x240) > r4:805228f4 r3:00000000 > [<802d9cac>] (rt_spin_lock_slowlock+0x0/0x240) from [<802da234>] > (rt_spin_lock+0x10/0x14) > [<802da224>] (rt_spin_lock+0x0/0x14) from [<8008694c>] > (__zone_pcp_update+0x58/0xd8) > [<800868f4>] (__zone_pcp_update+0x0/0xd8) from [<800603ec>] > (stop_machine_cpu_stop+0xb0/0x104) > [<8006033c>] (stop_machine_cpu_stop+0x0/0x104) from [<80060200>] > (cpu_stopper_thread+0xd4/0x188) > > > Signed-off-by: Aaditya Kumar > > --- > mm/page_alloc.c | 4 4 + 0 - 0 ! > 1 file changed, 4 insertions(+) > > Index: b/mm/page_alloc.c > =================================================================== > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3868,7 +3868,11 @@ static int __zone_pcp_update(void *data) > > void zone_pcp_update(struct zone *zone) > { > +#ifndef CONFIG_PREEMPT_RT_FULL > stop_machine(__zone_pcp_update, zone, NULL); > +#else > + __zone_pcp_update(zone); > +#endif > } > > static __meminit void zone_pcp_init(struct zone *zone) > > . > -- 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/