From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933387AbcBIWzw (ORCPT ); Tue, 9 Feb 2016 17:55:52 -0500 Received: from mga09.intel.com ([134.134.136.24]:56388 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932805AbcBIWzu (ORCPT ); Tue, 9 Feb 2016 17:55:50 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,423,1449561600"; d="scan'208";a="649781466" Date: Tue, 9 Feb 2016 22:55:49 +0000 From: Keith Busch To: Wenbo Wang Cc: Jens Axboe , Wenbo Wang , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "Wenwei.Tao" Subject: Re: [PATCH] NVMe: do not touch sq door bell if nvmeq has been suspended Message-ID: <20160209225548.GA32064@localhost.localdomain> References: <1454341324-21273-1-git-send-email-mail_weber_wang@163.com> <56AF8DB5.70206@fb.com> <20160203144123.GB23910@localhost.localdomain> <20160203163808.GC23910@localhost.localdomain> <20160208150132.GA25111@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 09, 2016 at 11:22:04AM +0000, Wenbo Wang wrote: > In most cases, rcu read lock is just a preempt_disable, which is what get_cpu does. I don't see any risk. Yes, many rcu_read_lock cases expand similarly to get_cpu. What about the other cases? FWIW, I don't think we'll hit the problem with the proposed rcu sync. Heck, we don't even have a synchronize today and we don't hit the theoretical problem.