Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757414AbbEVRr5 (ORCPT ); Fri, 22 May 2015 13:47:57 -0400 Received: from mga02.intel.com ([134.134.136.20]:24178 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756811AbbEVRr4 (ORCPT ); Fri, 22 May 2015 13:47:56 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,477,1427785200"; d="scan'208";a="575550836" Date: Fri, 22 May 2015 17:47:55 +0000 (UTC) From: Keith Busch X-X-Sender: vmware@localhost.lm.intel.com To: Parav Pandit cc: Keith Busch , linux-nvme@lists.infradead.org, Matthew Wilcox , Jens Axboe , linux-kernel@vger.kernel.org Subject: Re: [PATCH] NVMe: Avoid interrupt disable during queue init. In-Reply-To: Message-ID: References: <1432253553-17045-1-git-send-email-parav.pandit@avagotech.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1072 Lines: 32 On Fri, 22 May 2015, Parav Pandit wrote: > I agree to it that nvmeq won't be null after mb(); That alone is not sufficient. > > What I have proposed in previous email is, > > Converting, > > struct nvme_queue *nvmeq = dev->queues[i]; > if (!nvmeq) > continue; > spin_lock_irq(nvmeq->q_lock); > > to replace with, > > struct nvme_queue *nvmeq = rcu_dereference(dev->queues[i]); > if (!nvmeq) > continue; > spin_lock_irq(nvmeq->q_lock); > > This will prevent fetching content of q_lock before checking for NULL > condition. Classic usage or RCU. What the heck are you talking about? The value of dev->queue_count won't even let the thread iterate an nvmeq before q_lock is initialized. We used to rcu protect queue access, but that was to make nvme's make_request_fn safe to surprise removal, not for the polling thread. -- 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/