Re: WARNING: CPU: 3 PID: 1 at block/blk-mq-cpumap.c:90 blk_mq_map_hw_queues+0xf3/0x100

[Daniel Wagner]

On Wed, Jan 22, 2025 at 05:58:17PM -0500, Steven Rostedt wrote:
> On Wed, 22 Jan 2025 12:54:45 -0500
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> 
> > Not sure its related. I can see how reproducible this is, and if it is, I
> > can try to bisect it.
> 
> I bisected it down to: a5665c3d150c98 ("virtio: blk/scsi: replace
> blk_mq_virtio_map_queues with blk_mq_map_hw_queues")
> 
> And reverting that as well as:
> 
>   9bc1e897a821f ("blk-mq: remove unused queue mapping helpers")
> 
> It booted fine.

In the previous tests you just comment out the WARN_ON_ONCE or did you
also replace blk_mq_clear_mq_map with blk_mq_map_queues? The
blk_mq_clear_mq_map will map all queues to CPU 0 and if you offline CPU
0, there is nothing left to serve the hctx. I'll try to reproduce your
test and see if I my idea works.

Thanks,
Daniel