From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757683Ab0GNXae (ORCPT ); Wed, 14 Jul 2010 19:30:34 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:39059 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756776Ab0GNXad (ORCPT ); Wed, 14 Jul 2010 19:30:33 -0400 Date: Wed, 14 Jul 2010 16:30:29 -0700 From: "Paul E. McKenney" To: Josh Triplett 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: <20100714233029.GK2417@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100714200945.GA10535@linux.vnet.ibm.com> <1279138204-12849-29-git-send-email-paulmck@linux.vnet.ibm.com> <20100714211606.GB4624@feather> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100714211606.GB4624@feather> 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 02:16:06PM -0700, Josh Triplett wrote: > 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. Will give it a try! Thanx, Paul