Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751433AbWIONi7 (ORCPT ); Fri, 15 Sep 2006 09:38:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751437AbWIONi7 (ORCPT ); Fri, 15 Sep 2006 09:38:59 -0400 Received: from twin.jikos.cz ([213.151.79.26]:42454 "EHLO twin.jikos.cz") by vger.kernel.org with ESMTP id S1751433AbWIONi6 (ORCPT ); Fri, 15 Sep 2006 09:38:58 -0400 Date: Fri, 15 Sep 2006 15:38:51 +0200 (CEST) From: Jiri Kosina To: Dmitry Torokhov cc: Arjan van de Ven , lkml , Ingo Molnar Subject: Re: [PATCH 0/3] Synaptics - fix lockdep warnings In-Reply-To: Message-ID: References: <1158260584.4200.3.camel@laptopd505.fenrus.org> <1158298404.4332.18.camel@laptopd505.fenrus.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1412 Lines: 28 On Fri, 15 Sep 2006, Dmitry Torokhov wrote: > I understand what Ingo is saying about detecting deadlocks across the > pool of locks of the same class not waiting till they really clash, it > is really useful. I also want to make my code as independent of lockdep > as possible. Having a speciall marking on the locks themselves (done > upon creation) instead of altering call sites is the cleanest way IMHO. > Can we have a flag in the lock structure that would tell lockdep that it > is OK for the given lock to be taken several times (i.e. the locks are > really on the different objects)? This would still allow to detect > incorrect locking across different classes. Yes, but unfortunately marking the lock as 'can-be-taken-multiple-times' is weaker than using the nested locking provided by lockdep. i.e. if you mark a lock this way, it opens door for having deadlock, which won't be detected by lockdep. This will happen if the code, by mistake, really takes the _very same_ lock twice. lockdep will not be able to detect this, when the lock is marked in a way you propose, but is able to detect this when using the nested semantics. -- JiKos. - 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/