linux-kernel - Re: 4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with virtio-blk (also 4.12 stable)

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Date:   Mon, 18 Dec 2017 14:56:04 +0100
From:   Stefan Haberland <sth@...ux.vnet.ibm.com>
To:     Christoph Hellwig <hch@....de>,
        Christian Borntraeger <borntraeger@...ibm.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Bart Van Assche <Bart.VanAssche@....com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: 4.14: WARNING: CPU: 4 PID: 2895 at block/blk-mq.c:1144 with
 virtio-blk (also 4.12 stable)

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?
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>

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?