From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266010AbUGIWXh (ORCPT ); Fri, 9 Jul 2004 18:23:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266009AbUGIWXh (ORCPT ); Fri, 9 Jul 2004 18:23:37 -0400 Received: from mail.kroah.org ([69.55.234.183]:33958 "EHLO perch.kroah.org") by vger.kernel.org with ESMTP id S266006AbUGIWXf (ORCPT ); Fri, 9 Jul 2004 18:23:35 -0400 Date: Fri, 9 Jul 2004 15:21:54 -0700 From: Greg KH To: Andrew Morton Cc: Jesse Stockall , s.rivoir@gts.it, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu Subject: Re: 2.6.7-mm7 Message-ID: <20040709222154.GC6284@kroah.com> References: <20040708235025.5f8436b7.akpm@osdl.org> <40EE5418.2040000@gts.it> <20040709024112.7ef44d1d.akpm@osdl.org> <40EE732C.5020404@gts.it> <1089373506.8067.7.camel@homer.blizzard.org> <20040709115411.23d96699.akpm@osdl.org> <1089402736.8067.12.camel@homer.blizzard.org> <20040709130045.211b6d50.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040709130045.211b6d50.akpm@osdl.org> User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 09, 2004 at 01:00:45PM -0700, Andrew Morton wrote: > Jesse Stockall wrote: > > > > On Fri, 2004-07-09 at 14:54, Andrew Morton wrote: > > down_write_trylock(&usb_all_devices_rwsem)); > > > > > > That's a bit unusual. Could you (or Alan) please explain the reason for > > > this a little more? > > > > I believe you want this thread > > > > http://marc.theaimsgroup.com/?l=linux-usb-devel&m=108923404032264&w=2 > > Oh, OK. Recursively taking an rwsem for reading is certainly deadlocky. > The main reason for not supporting this is that heavy down_read() traffic > can trivially livelock down_write() waiters. Alan's patch will introduce > that shortcoming. > > Really, it would be better to get the locking sorted out. I agree, and we will before submitting the code to Linus. thanks, greg k-h