From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755231AbaEOXYP (ORCPT ); Thu, 15 May 2014 19:24:15 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39710 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752088AbaEOXYO (ORCPT ); Thu, 15 May 2014 19:24:14 -0400 Date: Thu, 15 May 2014 16:24:12 -0700 From: Andrew Morton To: riel@redhat.com Cc: linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, rdunlap@infradead.org, richard@nod.at, umgwanakikbuti@gmail.com Subject: Re: [PATCH 2/2] sysrq,rcu: suppress RCU stall warnings while sysrq runs Message-Id: <20140515162412.51355f308c34768ad08c0e2f@linux-foundation.org> In-Reply-To: <1398794796-17464-3-git-send-email-riel@redhat.com> References: <1398794796-17464-1-git-send-email-riel@redhat.com> <1398794796-17464-3-git-send-email-riel@redhat.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Apr 2014 14:06:36 -0400 riel@redhat.com wrote: > From: Rik van Riel > > Some sysrq handlers can run for a long time, because they dump a lot > of data onto a serial console. Having RCU stall warnings pop up in > the middle of them only makes the problem worse. > > This patch temporarily disables RCU stall warnings while a sysrq > request is handled. > > ... > > drivers/tty/sysrq.c | 3 +++ > include/linux/rcupdate.h | 12 ++++++++++++ > kernel/rcu/update.c | 12 ++++++++++++ OK, what's going on here. Someone (of, I suspect, a Paulish nature) has plucked out the rcu parts of this patch, put them in linux-next and omitted the drivers/tty part. Very tricky! I have done the opposite and have staged two patches against linux-next: http://ozlabs.org/~akpm/mmots/broken-out/sysrq-rcu-ify-__handle_sysrq.patch http://ozlabs.org/~akpm/mmots/broken-out/sysrqrcu-suppress-rcu-stall-warnings-while-sysrq-runs.patch Please check, review, comment, etc.