panic: non-current pmap 0xffffa00020eab8f0 on Rpi3

[bob prohaska]

On Mon, Oct 19, 2020 at 04:39:54PM -0400, Mark Johnston wrote:
> 
> I think vmspace_exit() should issue a release fence with the cmpset and
> an acquire fence when handling the refcnt == 1 case, but I don't see why
> that would make a difference here.  So, if you can test a debug patch,
> this one will yield a bit more debug info.  If you can provide access to
> a vmcore and kernel debug symbols, that'd be even better.
> 

I haven't seen an invalid pmap panic since the report of October 5th.
Your patch  applied cleanly on the Pi3 running HEAD at r366780M, 
the M being due to patches supplied by Kyle Evans applied to 
M       sys/arm/broadcom/bcm2835/bcm2835_mbox.c
M       sys/arm/broadcom/bcm2835/bcm2835_sdhci.c
M       sys/arm/broadcom/bcm2835/bcm2835_vcbus.c
M       sys/arm/broadcom/bcm2835/bcm2835_vcbus.h

AIUI, they're something to do with DMA for peripherals. They've 
caused no obvious trouble, if you anticipate conflicts let me know 
and I'll remove them 

I've never seen either a vmcore file or debug symbols on this machine.
A sequence of instructions to generate the data needed would be helpful.

Thanks for reading!

bob prohaska