From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: 4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable) To: Stefan Haberland , Christoph Hellwig , Jens Axboe Cc: Bart Van Assche , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Thomas Gleixner , linux-s390 , Martin Schwidefsky References: <20171123182542.GA2680@lst.de> <899f1638-cca4-28e6-3225-51505a053d45@de.ibm.com> <20171123183232.GA2845@lst.de> <92ef1aae-90b5-f14f-390e-bfab97899431@de.ibm.com> <419d8565-9cbe-16ac-3d5d-5945098694bc@de.ibm.com> <20171127155409.GA6937@lst.de> <20171204162108.GA12482@lst.de> <5ab91c56-b117-f4fa-3049-a4f8a5493155@de.ibm.com> <20171206232924.GA16584@lst.de> <0520e469-563b-486c-9ab8-00d8944ffa9d@linux.vnet.ibm.com> From: Christian Borntraeger Date: Wed, 20 Dec 2017 16:47:21 +0100 MIME-Version: 1.0 In-Reply-To: <0520e469-563b-486c-9ab8-00d8944ffa9d@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Message-Id: <04aff6c6-5c04-a2b5-e886-b747cb51f39e@de.ibm.com> List-ID: On 12/18/2017 02:56 PM, Stefan Haberland wrote: > On 07.12.2017 00:29, Christoph Hellwig wrote: >> On Wed, Dec 06, 2017 at 01:25:11PM +0100, Christian Borntraeger wrote: >> t > commit 11b2025c3326f7096ceb588c3117c7883850c068    -> bad >>>      blk-mq: create a blk_mq_ctx for each possible CPU >>> does not boot on DASD and >>> commit 9c6ae239e01ae9a9f8657f05c55c4372e9fc8bcc    -> good >>>     genirq/affinity: assign vectors to all possible CPUs >>> does boot with DASD disks. >>> >>> Also adding Stefan Haberland if he has an idea why this fails on DASD and adding Martin (for the >>> s390 irq handling code). >> That is interesting as it really isn't related to interrupts at all, >> it just ensures that possible CPUs are set in ->cpumask. >> >> I guess we'd really want: >> >> e005655c389e3d25bf3e43f71611ec12f3012de0 >> "blk-mq: only select online CPUs in blk_mq_hctx_next_cpu" >> >> before this commit, but it seems like the whole stack didn't work for >> your either. >> >> I wonder if there is some weird thing about nr_cpu_ids in s390? >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-s390" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at  http://vger.kernel.org/majordomo-info.html >> > > I tried this on my system and the blk-mq-hotplug-fix branch does not boot for me as well. > The disks get up and running and I/O works fine. At least the partition detection and EXT4-fs mount works. > > But at some point in time the disk do not get any requests. > > I currently have no clue why. > I took a dump and had a look at the disk states and they are fine. No error in the logs or in our debug entrys. Just empty DASD devices waiting to be called for I/O requests. > > Do you have anything I could have a look at? Jens, Christoph, so what do we do about this? To summarize: - commit 4b855ad37194f7 ("blk-mq: Create hctx for each present CPU") broke CPU hotplug. - Jens' quick revert did fix the issue and did not broke DASD support but has some issues with interrupt affinity. - Christoph patch set fixes the hotplug issue for virtio blk but causes I/O hangs on DASDs (even without hotplug). Christian