Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753357AbaLJBUX (ORCPT ); Tue, 9 Dec 2014 20:20:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38098 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752886AbaLJBUW (ORCPT ); Tue, 9 Dec 2014 20:20:22 -0500 Date: Wed, 10 Dec 2014 01:26:19 +0100 From: Oleg Nesterov To: "Paul E. McKenney" Cc: David Hildenbrand , linux-kernel@vger.kernel.org, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, rafael.j.wysocki@intel.com, peterz@infradead.org, bp@suse.de, jkosina@suse.cz Subject: Re: [PATCH v3] CPU hotplug: active_writer not woken up in some cases - deadlock Message-ID: <20141210002619.GB516@redhat.com> References: <1418127811-22629-1-git-send-email-dahi@linux.vnet.ibm.com> <20141209141903.GB25340@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141209141903.GB25340@linux.vnet.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 12/09, Paul E. McKenney wrote: > > Would wait_event()/wake_up() work for the wakeup-writer case? Yes, and in this case we could probably kill this puts_pending logic and avoid cpu_hotplug.lock in put_online_cpus() altogether? Can't we just make cpu_hotplug.refcount atomic_t? Anyway, this makes me think again that this code should use percpu_rwsem. Perhaps I'll try to make a patch next week... (we need down_write_recursive_readers(), and probably rcusync patches). Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/