[Bug 227404] UP FreeBSD VM always hangs on reboot since 20180329-r331740

[Dexuan Cui]

> From: Bruce Evans
> Sent: Tuesday, April 10, 2018 00:45
> 
> On Tue, 10 Apr 2018 a bug that doesn't want replies at freebsd.org wrote:
> 
> (The bug didn't even Cc freebsd-bugs for this followup.)

Thanks for the reminder! I Cc'd bugs@ just now.

> > --- Comment #4 from Dexuan Cui ---
> ...
> 
> I think I saw this a few months before that.
> 
> My only history of this is that I built a UP kernel on 17 Dec 2017 to see
> if UP kernels had the bug.  So SMP kernels probably had the bug then.
> 
> Bruce

Here the bug is that UP FreeBSD VM hangs on reboot or power-off, and
I'm sure this recent patch (which was commited by Jeff on Mar 26) caused this bug:
https://github.com/freebsd/freebsd/commit/63a483ed5f4eaadb8979992c7a5de24c7a471c61
("Fix a bug introduced in r329612 that slowly invalidates all clean bufs").

However, SMP VM with 2 or more CPUs doesn't hang on reboot/power-off
according to our tests.

Thanks,
-- Dexuan