From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932072AbWGKSVh (ORCPT ); Tue, 11 Jul 2006 14:21:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932077AbWGKSVh (ORCPT ); Tue, 11 Jul 2006 14:21:37 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:24216 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S932072AbWGKSVg (ORCPT ); Tue, 11 Jul 2006 14:21:36 -0400 Date: Tue, 11 Jul 2006 11:22:15 -0700 From: "Paul E. McKenney" To: Alan Stern Cc: Matt Helsley , Andrew Morton , dipankar@in.ibm.com, Ingo Molnar , tytso@us.ibm.com, Darren Hart , oleg@tv-sign.ru, Jes Sorensen , LKML Subject: Re: SRCU-based notifier chains Message-ID: <20060711182215.GF1288@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <20060711173906.GC1288@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 11, 2006 at 02:03:50PM -0400, Alan Stern wrote: > On Tue, 11 Jul 2006, Paul E. McKenney wrote: > > > Looks sane to me. A couple of minor comments interspersed. > > Okay, I'll submit it with a proper writeup. > > > > +/* > > > + * SRCU notifier chain routines. Registration and unregistration > > > + * use a mutex, and call_chain is synchronized by SRCU (no locks). > > > + */ > > > > Hmmm... Probably my just failing to pay attention, but haven't noticed > > the double-header-comment style before. > > As far as I know, I made it up. It seemed appropriate, since the first > header applies to the entire group of three routines that follow whereas > the second header is kerneldoc just for the next function. Fair enough -- I missed the fact that the first header applies to all three functions. > > > /* > > > - * Notifier chains are of three types: > > > + * Notifier chains are of four types: > > > > Is it possible to subsume one of the other three types? > > > > Might not be, but have to ask... > > In principle we could replace blocking notifiers, but in practice we > can't. > > We can't just substitute one for the other for two reasons: SRCU notifiers > need special initialization which the blocking notifiers don't have, and > SRCU notifiers have different time/space tradeoffs which might not be > appropriate for all existing blocking notifiers. Again, fair enough! Thanx, Paul