Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262163AbVERKlD (ORCPT ); Wed, 18 May 2005 06:41:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262161AbVERKlC (ORCPT ); Wed, 18 May 2005 06:41:02 -0400 Received: from rev.193.226.233.9.euroweb.hu ([193.226.233.9]:26643 "EHLO dorka.pomaz.szeredi.hu") by vger.kernel.org with ESMTP id S262162AbVERKiW (ORCPT ); Wed, 18 May 2005 06:38:22 -0400 To: dhowells@redhat.com 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 In-reply-to: <6865.1116412354@redhat.com> (message from David Howells on Wed, 18 May 2005 11:32:34 +0100) Subject: Re: [PATCH] fix race in mark_mounts_for_expiry() 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> Message-Id: From: Miklos Szeredi Date: Wed, 18 May 2005 12:37:27 +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 789 Lines: 19 > > How about this patch? It tries to solve this race without additional > > locking. If refcount is already zero, it will increment and decrement > > it. So be careful to only call grab_namespace() with vfsmount_lock > > held, otherwise it could race with itself. (vfsmount_lock is also > > needed in this case so that mnt->mnt_namespace, doesn't change, while > > grabbing the namespace) > > How about using cmpxchg? How? If the count is nonzero, an incremented count must be stored. You can't do that atomically with cmpxchg. Miklos - 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/