From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756730AbZCUHj4 (ORCPT ); Sat, 21 Mar 2009 03:39:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753457AbZCUHjo (ORCPT ); Sat, 21 Mar 2009 03:39:44 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:52056 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753336AbZCUHjn (ORCPT ); Sat, 21 Mar 2009 03:39:43 -0400 To: Andrew Morton Cc: Ingo Molnar , Jan Beulich , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, Gautham R Shenoy , Peter Zijlstra , Alexey Dobriyan , References: <49B91A7E.76E4.0078.0@novell.com> <1236934491.5188.209.camel@laptop> <49BA33BE.76E4.0078.0@novell.com> <1236937423.22914.3698.camel@twins> <20090313103828.GB31094@elte.hu> <20090320085205.GB16021@elte.hu> <20090320182404.GA31629@elte.hu> <1237575134.4667.5.camel@laptop> <1237577688.4667.68.camel@laptop> From: ebiederm@xmission.com (Eric W. Biederman) Date: Sat, 21 Mar 2009 00:39:28 -0700 In-Reply-To: <1237577688.4667.68.camel@laptop> (Peter Zijlstra's message of "Fri\, 20 Mar 2009 20\:34\:48 +0100") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in01.mta.xmission.com;;;ip=67.169.126.145;;;frm=ebiederm@xmission.com;;;spf=neutral X-SA-Exim-Connect-IP: 67.169.126.145 X-SA-Exim-Rcpt-To: akpm@linux-foundation.org, netdev@vger.kernel.org, adobriyan@gmail.com, peterz@infradead.org, ego@in.ibm.com, linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, tglx@linutronix.de, jbeulich@novell.com, mingo@elte.hu X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa04 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Andrew Morton X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 3.0 XMNoVowels Alpha-numberic number with no vowels * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa04 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral Subject: [PATCH 0/2] sysctl: lockdep support. X-SA-Exim-Version: 4.2.1 (built Thu, 25 Oct 2007 00:26:12 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The problem: There is a class of deadlocks that we currently have in the kernel that lockdep does not recognize. In particular with the network stack we can have: rtnl_lock(); use_table(); unregister_netdevice(); rtnl_lock(); unregister_sysctl_table(); .... wait_for_completion(); rtnl_lock(); .... unuse_table() rtnl_unlock(); complete(); Where we never make it to the lines labled .... My patch following patches treats the sysctl use count as a read/writer lock for purposes of lockdep. The code works but I'm not certain I have plugged into lockdep quite correctly. Eric