From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757622Ab0GNVWE (ORCPT ); Wed, 14 Jul 2010 17:22:04 -0400 Received: from slow3-v.mail.gandi.net ([217.70.178.89]:59834 "EHLO slow3-v.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752566Ab0GNVWB (ORCPT ); Wed, 14 Jul 2010 17:22:01 -0400 X-WhiteListed: mail was accepted with no delay X-WhiteListed: mail was accepted with no delay X-Originating-IP: 217.70.178.41 X-Originating-IP: 74.107.143.84 Date: Wed, 14 Jul 2010 14:16:06 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com Subject: Re: [PATCH RFC tip/core/rcu 29/30] rcu: add boot parameter to suppress RCU CPU stall warning messages Message-ID: <20100714211606.GB4624@feather> References: <20100714200945.GA10535@linux.vnet.ibm.com> <1279138204-12849-29-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1279138204-12849-29-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 14, 2010 at 01:10:03PM -0700, Paul E. McKenney wrote: > Although the RCU CPU stall warning messages are a very good way to alert > people to a problem, once alerted, it is sometimes helpful to shut them > off in order to avoid obscuring other messages that might be being used > to track down the problem. Although you can rebuild the kernel with > CONFIG_RCU_CPU_STALL_DETECTOR=n, this is sometimes inconvenient. This > commit therefore adds a boot parameter named "rcu_cpu_stall_suppress" > that shuts these messages off without requiring a rebuild (though a > reboot might be needed for those not brave enough to patch their kernel > while it is running). > > This message-suppression was already in place for the panic case, so this > commit need only rename the variable and export it via module_param(). > > Signed-off-by: Paul E. McKenney > --- > kernel/rcutree.c | 11 ++++++++--- > 1 files changed, 8 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 5b1c3c2..f3d5906 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -143,6 +143,11 @@ module_param(blimit, int, 0); > module_param(qhimark, int, 0); > module_param(qlowmark, int, 0); > > +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR > +int rcu_cpu_stall_suppress __read_mostly; > +module_param(rcu_cpu_stall_suppress, int, 0); > +#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ In theory, you could change the permissions on this module_param from 0 to 0644, making it appear under /sys as a writable file. That would allow changing it at runtime rather than just at boot time. Looking at the use of this variable, changing it dynamically should work. - Josh Triplett