Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934051AbbGHLx0 (ORCPT ); Wed, 8 Jul 2015 07:53:26 -0400 Received: from mail-ig0-f177.google.com ([209.85.213.177]:33577 "EHLO mail-ig0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932480AbbGHLxW (ORCPT ); Wed, 8 Jul 2015 07:53:22 -0400 MIME-Version: 1.0 In-Reply-To: <1435847397-724-4-git-send-email-akinobu.mita@gmail.com> References: <1435847397-724-1-git-send-email-akinobu.mita@gmail.com> <1435847397-724-4-git-send-email-akinobu.mita@gmail.com> Date: Wed, 8 Jul 2015 19:53:21 +0800 Message-ID: Subject: Re: [PATCH v2 3/6] blk-mq: fix q->mq_usage_counter access race From: Ming Lei To: Akinobu Mita Cc: Linux Kernel Mailing List , Jens Axboe 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: 1898 Lines: 58 On Thu, Jul 2, 2015 at 10:29 PM, Akinobu Mita wrote: > CPU hotplug handling for blk-mq (blk_mq_queue_reinit) accesses > q->mq_usage_counter while freezing all request queues in all_q_list. > On the other hand, q->mq_usage_counter is deinitialized in > blk_mq_free_queue() before deleting the queue from all_q_list. > > So if CPU hotplug event occurs in the window, percpu_ref_kill() is > called with q->mq_usage_counter which has already been marked dead, > and it triggers warning. Fix it by deleting the queue from all_q_list > earlier than destroying q->mq_usage_counter. > > Signed-off-by: Akinobu Mita > Cc: Jens Axboe > Cc: Ming Lei Reviewed-by: Ming Lei > --- > block/blk-mq.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index c5da908..ff72e18 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2070,15 +2070,16 @@ void blk_mq_free_queue(struct request_queue *q) > { > struct blk_mq_tag_set *set = q->tag_set; > > + mutex_lock(&all_q_mutex); > + list_del_init(&q->all_q_node); > + mutex_unlock(&all_q_mutex); > + > blk_mq_del_queue_tag_set(q); > > blk_mq_exit_hw_queues(q, set, set->nr_hw_queues); > blk_mq_free_hw_queues(q, set); > > percpu_ref_exit(&q->mq_usage_counter); > - mutex_lock(&all_q_mutex); > - list_del_init(&q->all_q_node); > - mutex_unlock(&all_q_mutex); > } > > /* Basically redo blk_mq_init_queue with queue frozen */ > -- > 1.9.1 > -- Ming Lei -- 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/