Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757653AbbEVQsr (ORCPT ); Fri, 22 May 2015 12:48:47 -0400 Received: from mail-ie0-f180.google.com ([209.85.223.180]:35966 "EHLO mail-ie0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756992AbbEVQso (ORCPT ); Fri, 22 May 2015 12:48:44 -0400 MIME-Version: 1.0 In-Reply-To: References: <1432253553-17045-1-git-send-email-parav.pandit@avagotech.com> Date: Fri, 22 May 2015 22:18:43 +0530 Message-ID: Subject: Re: [PATCH] NVMe: Avoid interrupt disable during queue init. From: Parav Pandit To: Keith Busch Cc: linux-nvme@lists.infradead.org, Matthew Wilcox , Jens Axboe , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1471 Lines: 35 On Fri, May 22, 2015 at 9:53 PM, Keith Busch wrote: > On Fri, 22 May 2015, Parav Pandit wrote: >> >> During normal positive path probe, >> (a) device is added to dev_list in nvme_dev_start() >> (b) nvme_kthread got created, which will eventually refers to >> dev->queues[qid] to check for NULL. >> (c) dev_start() worker thread has started probing device and creating >> the queue using nvme_alloc_queue >> This is is assigning the dev->queue[qid] new pointer. >> If this is done out of order, nvme_kthread will pickup uninitialized >> q_lock, cq_phase, q_db. > > > A memory barrier before incrementing the dev->queue_count (and assigning > the pointer in the array before that) should address this concern. > Sure. mb() will solve the publisher side problem. RCU is wrapper around mb(). However mb() doesn't solve the issue of q_lock variable getting fetched before if (!nvmeq) condition being executed, by value compilation optimizations in nvme_kthread(). So I was inclined towards more preferred method of rcu. >> Other thoughts to not create nvme_kthread until all the queues are active. > > > No good, we want to poll during queue creation to detect controller > errors and broken interrupts. -- 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/