From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752562Ab3FZOvW (ORCPT ); Wed, 26 Jun 2013 10:51:22 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:21780 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751355Ab3FZOvR (ORCPT ); Wed, 26 Jun 2013 10:51:17 -0400 X-Authority-Analysis: v=2.0 cv=KtrPKBqN c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=k2iftdwf7gsA:10 a=5SG0PmZfjMsA:10 a=IkcTkHD0fZMA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=lolsShB3EWcA:10 a=SwdnOlKBk8mc9e08x5sA:9 a=QEXdDO2ut3YA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-ID: <1372258271.18733.256.camel@gandalf.local.home> Subject: Re: [PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline From: Steven Rostedt To: paulmck@linux.vnet.ibm.com Cc: David Laight , "Srivatsa S. Bhat" , peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, walken@google.com, mingo@kernel.org, linux-arch@vger.kernel.org, vincent.guittot@linaro.org, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, namhyung@kernel.org, tglx@linutronix.de, laijs@cn.fujitsu.com, zhong@linux.vnet.ibm.com, netdev@vger.kernel.org, oleg@redhat.com, sbw@mit.edu, tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Date: Wed, 26 Jun 2013 10:51:11 -0400 In-Reply-To: <20130626143424.GN3828@linux.vnet.ibm.com> References: <20130625202452.16593.22810.stgit@srivatsabhat.in.ibm.com> <20130625202755.16593.67819.stgit@srivatsabhat.in.ibm.com> <20130625220026.GG3828@linux.vnet.ibm.com> <51CAF624.6060004@linux.vnet.ibm.com> <20130626143424.GN3828@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2013-06-26 at 07:34 -0700, Paul E. McKenney wrote: > On Wed, Jun 26, 2013 at 03:29:40PM +0100, David Laight wrote: > > > Once stop_machine() is gone from the CPU offline path, we won't be able > > > to depend on disabling preemption to prevent CPUs from going offline > > > from under us. > > > > Could you use an rcu-like sequence so that disabling pre-emption > > would be enough? > > > > Something like rebuilding the cpu list, then forcing yourself > > to run on all the cpu. > > > > That would be far less intrusive. > > It would also increase the latency of CPU-hotunplug operations. > Is that a big deal? -- Steve