Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262184AbVERLw0 (ORCPT ); Wed, 18 May 2005 07:52:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262169AbVERLwZ (ORCPT ); Wed, 18 May 2005 07:52:25 -0400 Received: from mx1.redhat.com ([66.187.233.31]:29120 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S262180AbVERLwK (ORCPT ); Wed, 18 May 2005 07:52:10 -0400 From: David Howells In-Reply-To: References: <1116005355.6248.372.camel@localhost> <1116012287.6248.410.camel@localhost> <1116013840.6248.429.camel@localhost> <1116256279.4154.41.camel@localhost> <20050516111408.GA21145@mail.shareable.org> <1116301843.4154.88.camel@localhost> <20050517012854.GC32226@mail.shareable.org> <1116360352.24560.85.camel@localhost> <1116399887.24560.116.camel@localhost> <1116400118.24560.119.camel@localhost> <6865.1116412354@redhat.com> <7230.1116413175@redhat.com> <8247.1116413990@redhat.com> To: Miklos Szeredi Cc: linuxram@us.ibm.com, jamie@shareable.org, viro@parcelfarce.linux.theplanet.co.uk, akpm@osdl.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] fix race in mark_mounts_for_expiry() X-Mailer: MH-E 7.82; nmh 1.0.4; GNU Emacs 22.0.50.1 Date: Wed, 18 May 2005 12:51:39 +0100 Message-ID: <9498.1116417099@redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1076 Lines: 25 Miklos Szeredi wrote: > Do you think my original fix is wrong, or is this just cosmetics? What you're doing is tricky. It's asking for a race. Admittedly, it may not occur in the particular situation you're looking at, but can you always guarantee that? Remember, it may be a race against some piece of code that's not yet written, by an author who doesn't realise what _you_ are doing here because their changeset doesn't intersect with yours. Remember: you have, in effect, made the usage count on that structure non-atomic. I do something like that in rwsems and it's something I have to be very careful about. The main reason I can get away with it is that the actual implementation of rwsems is small and is located in a very restrictes set of places and it's not intermingled with other stuff. David - 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/