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

[Christoph Hellwig]

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?