From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423747Ab2LGSQS (ORCPT ); Fri, 7 Dec 2012 13:16:18 -0500 Received: from mail-pb0-f46.google.com ([209.85.160.46]:38305 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423669Ab2LGSQP (ORCPT ); Fri, 7 Dec 2012 13:16:15 -0500 Date: Fri, 7 Dec 2012 10:16:08 -0800 From: Tejun Heo To: "Srivatsa S. Bhat" Cc: tglx@linutronix.de, peterz@infradead.org, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, vincent.guittot@linaro.org, oleg@redhat.com, sbw@mit.edu, amit.kucheria@linaro.org, rostedt@goodmis.org, rjw@sisk.pl, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3 1/9] CPU hotplug: Provide APIs to prevent CPU offline from atomic context Message-ID: <20121207181608.GB2821@htj.dyndns.org> References: <20121207173702.27305.1486.stgit@srivatsabhat.in.ibm.com> <20121207173759.27305.84316.stgit@srivatsabhat.in.ibm.com> <20121207175724.GA2821@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121207175724.GA2821@htj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, again. On Fri, Dec 07, 2012 at 09:57:24AM -0800, Tejun Heo wrote: > possible. Also, I think the right approach would be auditing each > get_online_cpus_atomic() callsites and figure out proper locking order > rather than implementing a construct this unusual especially as > hunting down the incorrect cases shouldn't be difficult given proper > lockdep annotation. On the second look, it looks like you're implementing proper percpu_rwlock semantics as readers aren't supposed to induce circular dependency directly. Can you please work with Oleg to implement proper percpu-rwlock and use that for CPU hotplug rather than implementing it inside CPU hotplug? Thanks. -- tejun