From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Lei Subject: Re: [PATCH] blk-mq: Fix several SCSI request queue lockups Date: Tue, 5 Dec 2017 09:18:51 +0800 Message-ID: <20171205011850.GD8365@ming.t460p> References: <20171204173032.16330-1-bart.vanassche@wdc.com> <20171204224200.GA6888@ming.t460p> <1512427697.2795.14.camel@wdc.com> <20171204230151.GD6888@ming.t460p> <1512430346.2795.34.camel@wdc.com> <20171205002040.GA8365@ming.t460p> <1512433798.2795.45.camel@wdc.com> <20171205010428.GB8365@ming.t460p> <1512436422.2795.47.camel@wdc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1512436422.2795.47.camel@wdc.com> Sender: linux-block-owner@vger.kernel.org To: Bart Van Assche Cc: "jthumshirn@suse.de" , "linux-block@vger.kernel.org" , "hch@lst.de" , "martin.petersen@oracle.com" , "axboe@kernel.dk" , "linux-scsi@vger.kernel.org" , "hare@suse.com" , "jejb@linux.vnet.ibm.com" List-Id: linux-scsi@vger.kernel.org On Tue, Dec 05, 2017 at 01:13:43AM +0000, Bart Van Assche wrote: > On Tue, 2017-12-05 at 09:04 +0800, Ming Lei wrote: > > Then no reason to revert commit(0df21c86bdbf scsi: implement .get_budget an > > .put_budget for blk-mq) for one issue which may never happen in reality since > > this reproducer need out-of-tree patch. > > Sorry but I disagree completely. You seem to overlook that there may be other > circumstances that trigger the same lockup, e.g. a SCSI queue full condition. If the scsi_dev_queue_ready() returns false, .get_budget() catches that and never add request to hctx->dispatch. And scsi_host_queue_ready() always returns true, since we respect per-host queue depth by blk_mq_get_driver_tag() before calling .queue_rq(). Or if I miss other cases, please point it out. -- Ming