Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753018AbbGRQ3E (ORCPT ); Sat, 18 Jul 2015 12:29:04 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:35296 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752899AbbGRQ3A (ORCPT ); Sat, 18 Jul 2015 12:29:00 -0400 From: Akinobu Mita To: linux-kernel@vger.kernel.org Cc: Akinobu Mita , Jens Axboe , Ming Lei Subject: [PATCH v3 4/7] blk-mq: fix q->mq_usage_counter access race Date: Sun, 19 Jul 2015 01:28:20 +0900 Message-Id: <1437236903-31617-5-git-send-email-akinobu.mita@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1437236903-31617-1-git-send-email-akinobu.mita@gmail.com> References: <1437236903-31617-1-git-send-email-akinobu.mita@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1659 Lines: 50 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 Reviewed-by: Ming Lei Cc: Jens Axboe Cc: 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 9328405..d5d93e0 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2077,15 +2077,16 @@ 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 -- 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/