Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262158AbVERKyi (ORCPT ); Wed, 18 May 2005 06:54:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262161AbVERKyi (ORCPT ); Wed, 18 May 2005 06:54:38 -0400 Received: from rev.193.226.233.9.euroweb.hu ([193.226.233.9]:14863 "EHLO dorka.pomaz.szeredi.hu") by vger.kernel.org with ESMTP id S262158AbVERKyb (ORCPT ); Wed, 18 May 2005 06:54:31 -0400 To: dhowells@redhat.com CC: miklos@szeredi.hu, 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: <7230.1116413175@redhat.com> (message from David Howells on Wed, 18 May 2005 11:46:15 +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> <7230.1116413175@redhat.com> Message-Id: From: Miklos Szeredi Date: Wed, 18 May 2005 12:53:28 +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 795 Lines: 29 > Yes you can. cmpxchg() is atomic. Several archs implement atomic_inc() and co > with cmpxchg() or similar. > > Something like: > > static inline struct namespace *grab_namespace(struct namespace *n) > { > int old = atomic_read(&n->count); > > while (old > 0) { > /* attempt to increment the counter */ > old = cmpxchg(&n->count, old, old + 1); > } > > return old > 0 ? n : NULL; > } > Ahh OK :) There's still the problem of cmpxchg meddling in the internals of an atomic_t. Is that OK? Will that work on all archs? 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/