On Wed, 13 May 2020 18:15:57 +0200
Sven Schnelle <svens@linux.ibm.com> wrote:

> Thanks for looking into this. I've attached my /proc/config.gz to this Mail.
> The x86 system is my Laptop which is a Thinkpad X280 with 4 HT CPUs (so 8 cpus
> in total). I've tried disabling preemption, but this didn't help.
> 
> It's always this check that causes the loop:
> 
> if (iter->head >= rb_page_size(iter->head_page)) {
> 	rb_inc_iter(iter);
> 	goto again;
> }
> 
> On the first loop iter->head is some value > 0 and rb_page_size returns
> 0, afterwards it gets twice to this check with both values 0. The third
> time the warning is triggered. Maybe that information helps.

Letting it run long enough, I was able to trigger it.

I think I know what's wrong with it. I'll put in some debugging to see if
my thoughts are accurate.

Thanks for bringing this back to my attention.

-- Steve