From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754471AbaBFSlw (ORCPT ); Thu, 6 Feb 2014 13:41:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57679 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751296AbaBFSlu (ORCPT ); Thu, 6 Feb 2014 13:41:50 -0500 Date: Thu, 6 Feb 2014 19:41:03 +0100 From: Oleg Nesterov To: "Srivatsa S. Bhat" Cc: paulus@samba.org, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org, mingo@kernel.org, paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, Toshi Kani , "Rafael J. Wysocki" Subject: Re: [PATCH 01/51] CPU hotplug: Provide lockless versions of callback registration functions Message-ID: <20140206184103.GA31410@redhat.com> References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> <20140205220447.19080.9460.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140205220447.19080.9460.stgit@srivatsabhat.in.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/06, Srivatsa S. Bhat wrote: > > The following method of CPU hotplug callback registration is not safe > due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock > and the cpu_hotplug.lock. Off-topic, but perhaps it also makes sense to add the lockdep annotations later, to catch other similar problems. Currently get_online_cpus() acquires nothing from lockdep pov. As for the this patch/series, personally I agree. Oleg.