From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261474AbUIAARN (ORCPT ); Tue, 31 Aug 2004 20:17:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264531AbUIAAO3 (ORCPT ); Tue, 31 Aug 2004 20:14:29 -0400 Received: from rwcrmhc13.comcast.net ([204.127.198.39]:12261 "EHLO rwcrmhc13.comcast.net") by vger.kernel.org with ESMTP id S264261AbUIAAOB (ORCPT ); Tue, 31 Aug 2004 20:14:01 -0400 Subject: Re: [RFC&PATCH] Alternative RCU implementation From: Jim Houston Reply-To: jim.houston@comcast.net To: dipankar@in.ibm.com Cc: paulmck@us.ibm.com, linux-kernel@vger.kernel.org In-Reply-To: <20040830173853.GB4639@in.ibm.com> References: <20040830004322.GA2060@us.ibm.com> <1093886020.984.238.camel@new.localdomain> <20040830173853.GB4639@in.ibm.com> Content-Type: text/plain Organization: Message-Id: <1093997450.4069.1.camel@new.localdomain> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.2 (1.2.2-4) Date: 31 Aug 2004 20:10:50 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-08-30 at 13:38, Dipankar Sarma wrote: > > I'm also trying to figure out if I need the call_rcu_bh() changes. > > Since my patch will recognize a grace periods as soon as any > > pending read-side critical sections complete, I suspect that I > > don't need this change. > > Except that under a softirq flood, a reader in a different read-side > critical section may get delayed a lot holding up RCU. Let me know > if I am missing something here. Hi Dipankar, O.k. That makes sense. So the rcu_read_lock_bh(), rcu_read_unlock_bh() and call_rcu_bh() would be the preferred interface. Are there cases where they can't be used? How do you decide where to use the _bh flavor? I see that local_bh_enable() WARNS if interrupts are disabled. Is that the issue? Are rcu_read_lock()/rcu_read_unlock() ever called from code which disables interrupts? Jim Houston - Concurrent Computer Corp.