From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933532AbZJGNSN (ORCPT ); Wed, 7 Oct 2009 09:18:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933139AbZJGNSM (ORCPT ); Wed, 7 Oct 2009 09:18:12 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:37697 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933136AbZJGNSM (ORCPT ); Wed, 7 Oct 2009 09:18:12 -0400 Subject: Re: [PATCH tip/core/rcu 2/3] rcu: make hot-unplugged CPU relinquish its own RCU callbacks From: Steven Rostedt Reply-To: rostedt@goodmis.org To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com In-Reply-To: <1254890898456-git-send-email-> References: <20091007044748.GA12763@linux.vnet.ibm.com> <1254890898456-git-send-email-> Content-Type: text/plain Organization: Kihon Technologies Inc. Date: Wed, 07 Oct 2009 09:16:12 -0400 Message-Id: <1254921372.1696.132.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paul, Still suffering jetlag? ;-) On Tue, 2009-10-06 at 21:48 -0700, Paul E. McKenney wrote: > From: Paul E. McKenney > > The current interaction between RCU and CPU hotplug requires that > RCU block in CPU notifiers waiting for callbacks to drain. This can > be greatly simplified by haing each CPU relinquish its own callbacks, having > and for both _rcu_barrier() and CPU_DEAD notifiers to adopt all callbacks > that were previously relinquished. This change also eliminates the > possibility of certain types of hangs due to the previous practice of > waiting for callbacks to be invoked from within CPU notifiers. If you > don't every wait, you cannot hang. ever ;-) > > Signed-off-by: Paul E. McKenney -- Steve