From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa2.hgst.iphmx.com ([68.232.143.124]:22006 "EHLO esa2.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751100AbdCQX0g (ORCPT ); Fri, 17 Mar 2017 19:26:36 -0400 From: Bart Van Assche To: "linux-kernel@vger.kernel.org" , "hch@infradead.org" , "linux-block@vger.kernel.org" , "tom.leiming@gmail.com" , "axboe@fb.com" CC: "yizhan@redhat.com" , "tj@kernel.org" Subject: Re: [PATCH v1 3/3] blk-mq: start to freeze queue just after setting dying Date: Fri, 17 Mar 2017 23:26:26 +0000 Message-ID: <1489793173.2826.23.camel@sandisk.com> References: <20170317095711.5819-1-tom.leiming@gmail.com> <20170317095711.5819-4-tom.leiming@gmail.com> In-Reply-To: <20170317095711.5819-4-tom.leiming@gmail.com> Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Fri, 2017-03-17 at 17:57 +0800, Ming Lei wrote: > Given blk_set_queue_dying() is always called in remove path > of block device, and queue will be cleaned up later, we don't > need to worry about undoing the counter. >=20 > diff --git a/block/blk-core.c b/block/blk-core.c > index d772c221cc17..62d4967c369f 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -500,9 +500,12 @@ void blk_set_queue_dying(struct request_queue *q) > queue_flag_set(QUEUE_FLAG_DYING, q); > spin_unlock_irq(q->queue_lock); > =20 > - if (q->mq_ops) > + if (q->mq_ops) { > blk_mq_wake_waiters(q); > - else { > + > + /* block new I/O coming */ > + blk_mq_freeze_queue_start(q); > + } else { > struct request_list *rl; > =20 > spin_lock_irq(q->queue_lock); Hello Ming, The blk_freeze_queue() call in blk_cleanup_queue() waits until q_usage_coun= ter drops to zero. Since the above blk_mq_freeze_queue_start() call increases t= hat counter by one, how is blk_freeze_queue() expected to finish ever? Bart.=