From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757218Ab1AMPok (ORCPT ); Thu, 13 Jan 2011 10:44:40 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:50569 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757207Ab1AMPoi (ORCPT ); Thu, 13 Jan 2011 10:44:38 -0500 Date: Thu, 13 Jan 2011 07:42:57 -0800 From: "Paul E. McKenney" To: Thomas Weber Cc: Russell King , Linux Kernel List Subject: Re: INFO: task rcu_kthread:6 blocked for more than 120 seconds. Message-ID: <20110113154257.GK17328@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110112174300.GA6504@flint.arm.linux.org.uk> <20110112222219.GA17328@linux.vnet.ibm.com> <4D2F179E.40401@corscience.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D2F179E.40401@corscience.de> User-Agent: Mutt/1.5.20 (2009-06-14) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 13, 2011 at 04:17:50PM +0100, Thomas Weber wrote: > Am 12.01.2011 23:22, schrieb Paul E. McKenney: > > On Wed, Jan 12, 2011 at 05:43:00PM +0000, Russell King wrote: > >> I'm seeing rcu_kthread get stuck from time to time on ARM Versatile PB > >> (ARM926). Kernel is based upon commit 9e9bc973 (immediately prior to > >> the merge of the OMAP tree.) > >> > >> ~ # ps aux|grep rcu > >> root 6 0.0 0.0 0 0 ? S 02:31 0:01 [rcu_kthread] > >> root 502 9.0 0.3 3740 472 ttyAMA0 S+ 02:59 0:00 grep rcu > >> ~ # ps aux|grep rcu > >> root 6 0.0 0.0 0 0 ? D 02:31 0:01 [rcu_kthread] > >> root 504 0.0 0.3 3740 472 ttyAMA0 S+ 03:00 0:00 grep rcu > >> ~ # ps aux|grep rcu > >> root 6 0.0 0.0 0 0 ? D 02:31 0:01 [rcu_kthread] > >> root 506 0.0 0.3 3740 472 ttyAMA0 S+ 03:00 0:00 grep rcu > >> ~ # ps aux|grep rcu > >> root 6 0.0 0.0 0 0 ? D 02:31 0:01 [rcu_kthread] > >> root 508 0.0 0.3 3740 472 ttyAMA0 S+ 03:00 0:00 grep rcu > >> ~ # cat /proc/6/wchan > >> rcu_kthread > >> ~ # INFO: task rcu_kthread:6 blocked for more than 120 seconds. > >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > >> rcu_kthread D c02c6684 0 6 2 0x00000000 > >> Backtrace: > >> [] (schedule+0x0/0x354) from [] (rcu_kthread+0x78/0xf4) > >> [] (rcu_kthread+0x0/0xf4) from [] (kthread+0x88/0x90) > >> [] (kthread+0x0/0x90) from [] (do_exit+0x0/0x5f8) > >> r7:00000013 r6:c004d12c r5:c0063324 r4:c181df28 > >> no locks held by rcu_kthread/6. > > > > Does the following patch help? > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 70ce43253a4465211a9c51e33d56a417c759a718 > > Author: Paul E. McKenney > > Date: Wed Jan 12 14:18:11 2011 -0800 > > > > rcu: avoid pointless blocked-task warnings > > > > If the RCU callback-processing kthread has nothing to do, it parks in > > a wait_event(). If RCU remains idle for more than two minutes, the > > kernel complains about this. This commit changes from wait_event() > > to wait_event_interruptible() to prevent the kernel from complaining > > just because RCU is idle. > > > > Reported-by: Russell King > > Signed-off-by: Paul E. McKenney > > > > diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c > > index 0344937..0c343b9 100644 > > --- a/kernel/rcutiny.c > > +++ b/kernel/rcutiny.c > > @@ -189,7 +189,8 @@ static int rcu_kthread(void *arg) > > unsigned long flags; > > > > for (;;) { > > - wait_event(rcu_kthread_wq, have_rcu_kthread_work != 0); > > + wait_event_interruptible(rcu_kthread_wq, > > + have_rcu_kthread_work != 0); > > morework = rcu_boost(); > > local_irq_save(flags); > > work = have_rcu_kthread_work; > > -- > > 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/ > > Hello Paul, > here it helps. Tested on Devkit8000 (omap3, beagleboard clone). Without > this patch I had permanent crashes. With this patch board is running. > > Tested-by: Thomas Weber Thank you, Thomas!!! I have added your Tested-by. Thanx, Paul