Re: Xen panic in lwp_need_userret()

[Andrew Doran <ad%netbsd.org@localhost>]

Hi,

On Fri, Nov 29, 2019 at 09:42:44AM +0100, Manuel Bouyer wrote:

> > Yes indeed, since yesterday with rev 1.51 src/sys/kern/kern_softint.c.
> 
> Well, the 201911261940Z now panics with:
> [   1.0000000] xenbus0 at hypervisor0: Xen Virtual Bus Interface
> [   1.0000000] xencons0 at hypervisor0: Xen Virtual Console Driver
> [   1.0000030] panic: kernel diagnostic assertion "(flags & RESCHED_UPREEMPT) != 0" failed: file "/home/source/ab/HEAD/src/sys/arch/x86/x86/x86_machdep.c", line 317 
> [   1.0000030] cpu0: Begin traceback...
> [   1.0000030] vpanic() at netbsd:vpanic+0x146
> [   1.0000030] kern_assert() at netbsd:kern_assert+0x48
> [   1.0000030] cpu_need_resched() at netbsd:cpu_need_resched+0xb3
> [   1.0000030] hardclock() at netbsd:hardclock+0xc4
> [   1.0000030] xen_timer_handler() at netbsd:xen_timer_handler+0x66
> [   1.0000030] Xresume_xenev7() at netbsd:Xresume_xenev7+0x49
> [   1.0000030] --- interrupt ---
> [   1.0000030] Xspllower() at netbsd:Xspllower+0xe
> [   1.0000030] cpu0: End traceback...
> 
> (http://www-soc.lip6.fr/~bouyer/NetBSD-tests/xen/HEAD/amd64/201911261940Z_anita.txt)

You have a CPU hog stuck in kernel and it's trying to force it off with a
kernel preemption, but NetBSD/xen doesn't have kernel preemption.  I'll
fix it when I get home from work later.

Andrew