Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757477AbZISLUL (ORCPT ); Sat, 19 Sep 2009 07:20:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752226AbZISLUH (ORCPT ); Sat, 19 Sep 2009 07:20:07 -0400 Received: from casper.infradead.org ([85.118.1.10]:38748 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752106AbZISLUF (ORCPT ); Sat, 19 Sep 2009 07:20:05 -0400 Subject: Re: circular locking dependency detected panic in filldir when CONFIG_PROVE_LOCKING=y From: Peter Zijlstra To: Ingo Molnar Cc: Trond Myklebust , Andrew Morton , Joe Korty , Al Viro , Steve French , LKML In-Reply-To: <20090919072349.GC15292@elte.hu> References: <20090918211550.GA8258@tsunami.ccur.com> <1253309941.3183.104.camel@heimdal.trondhjem.org> <20090919072349.GC15292@elte.hu> Content-Type: text/plain Date: Sat, 19 Sep 2009 13:19:48 +0200 Message-Id: <1253359188.7085.0.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1745 Lines: 44 On Sat, 2009-09-19 at 09:23 +0200, Ingo Molnar wrote: > * Trond Myklebust wrote: > > > On Fri, 2009-09-18 at 17:15 -0400, Joe Korty wrote: > > > I experienced a might_fault panic from NFS's use of filldir > > > in a 2.6.31 kernel compiled with CONFIG_PROVE_LOCKING=y. > > > > > > Looking at filldir, I see it is accessing user space with > > > __put_dir's (which are inatomic) and with one copy_to_user > > > (which is not inatomic). It is the single copy_to_user > > > which is causing the might_fault panic. > > > > > > It doesn't make any sense to be mixing use of inatomic > > > and non-inatomic services in filldir. Either all should be > > > the inatomic version, or none should be. > > > > > > The might_fault condition being reported by the panic looks > > > real to me, so I suspect the wrong answer is converting > > > everything to the inatomic version, since that just > > > suppresses the circular dependency check while leaving > > > the circular dependency in place. > > > > Yes. This is known... Please see > > http://thread.gmane.org/gmane.linux.nfs/28578 > > and > > http://thread.gmane.org/gmane.linux.nfs/27406 > > > > I'm still hoping the VM folks can see fit to merge Peter's fix at some > > point... > > Ouch, those patches at: > > http://programming.kicks-ass.net/kernel-patches/mmap-vs-nfs/ > > .... are 2 years old. Higher intensity prodding needed to get this > moving? No I just need to find a way to clone() myself :-) -- 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/