From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59528) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZK1xa-0000g9-24 for qemu-devel@nongnu.org; Tue, 28 Jul 2015 06:18:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZK1xV-0006fz-2f for qemu-devel@nongnu.org; Tue, 28 Jul 2015 06:18:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58793) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZK1xU-0006fj-Us for qemu-devel@nongnu.org; Tue, 28 Jul 2015 06:18:05 -0400 References: <55B6E854.9090600@cn.fujitsu.com> <55B75278.80909@redhat.com> <55B7532D.9010506@cn.fujitsu.com> From: Paolo Bonzini Message-ID: <55B756D8.9090503@redhat.com> Date: Tue, 28 Jul 2015 12:18:00 +0200 MIME-Version: 1.0 In-Reply-To: <55B7532D.9010506@cn.fujitsu.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 for-2.5] rcu: Allow calling rcu_(un)register_thread() during synchronize_rcu() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wen Congyang , qemu-devl On 28/07/2015 12:02, Wen Congyang wrote: > I have a question about rcu: while do we call wait_for_readers() > twice for 32-bit host? Because there is a very small but non-zero probability of the counter going up by exactly 2^31 periods (periods are stored in bits 1-31 so you lose one bit) while the thread is sleeping. This detail of the implementation comes from URCU. Paolo