Messages in this thread | | | Subject | Re: 4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable) | From | Stefan Haberland <> | Date | Thu, 11 Jan 2018 14:17:06 +0100 |
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On 11.01.2018 12:44, Christian Borntraeger wrote: > > On 01/11/2018 10:13 AM, Ming Lei wrote: >> On Wed, Dec 20, 2017 at 04:47:21PM +0100, Christian Borntraeger wrote: >>> 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). >> Hello, >> >> This one is a valid use case for VM, I think we need to fix that. >> >> Looks there is issue on the fouth patch("blk-mq: only select online >> CPUs in blk_mq_hctx_next_cpu"), I fixed it in the following tree, and >> the other 3 patches are same with Christoph's: >> >> https://github.com/ming1/linux.git v4.15-rc-block-for-next-cpuhot-fix >> >> gitweb: >> https://github.com/ming1/linux/commits/v4.15-rc-block-for-next-cpuhot-fix >> >> Could you test it and provide the feedback? >> >> BTW, if it can't help this issue, could you boot from a normal disk first >> and dump blk-mq debugfs of DASD later? > That kernel seems to boot fine on my system with DASD disks. > > -- > 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 did some regression testing and it works quite well. Boot works, attaching CPUs during runtime on z/VM and enabling them in Linux works as well. I also did some DASD online/offline CPU enable/disable loops.
Regards, Stefan
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