From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:55072 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753707AbdLDK5d (ORCPT ); Mon, 4 Dec 2017 05:57:33 -0500 Date: Mon, 4 Dec 2017 18:57:21 +0800 From: Ming Lei To: Alban Browaeys , Paolo Valente Cc: Jens Axboe , linux-block@vger.kernel.org Subject: Re: blk-mq + bfq: udevd hang on usb2 storages Message-ID: <20171204105720.GA6884@ming.t460p> References: <1512147869.8698.21.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1512147869.8698.21.camel@gmail.com> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Fri, Dec 01, 2017 at 06:04:29PM +0100, Alban Browaeys wrote: > I initially reported as https://bugzilla.kernel.org/show_bug.cgi?id=198 > 023 . > > I have now bisected this issue to commit a6a252e6491443c1c1 "blk-mq- > sched: decide how to handle flush rq via RQF_FLUSH_SEQ". > > This is with an USB stick Sandisk Cruzer (USB Version: 2.10) I > regressed with. > systemctl restart systemd-udevd restores sanity. > > PS: With an USB3 Lexar (USB Version: 3.00) I get more severe an issue > (not bisected) where I find no way out of reboot. My report to bugzilla > has logs when I was swapping between the these keys. The logs attached > there mixes what looks like two different behaviors. Hi Paolo, >>From both Alban's trace and my trace, looks this issue is in BFQ, since request can't be retrieved via e->type->ops.mq.dispatch_request() in blk_mq_do_dispatch_sched() after it is inserted into BFQ's queue. https://bugzilla.kernel.org/show_bug.cgi?id=198023#c4 https://marc.info/?l=linux-block&m=151214241518562&w=2 BTW, I have tried to reproduce the issue with scsi_debug, but not succeed, and it can't be reproduced with other schedulers(mq-deadline, none) too. So could you take a look? Thanks, Ming