svn commit: r333703 - head/sys/vm

[Conrad Meyer]

On Wed, May 16, 2018 at 9:27 PM, Mark Johnston <markj at freebsd.org> wrote:
> Author: markj
> Date: Thu May 17 04:27:08 2018
> New Revision: 333703
> URL: https://svnweb.freebsd.org/changeset/base/333703
>
> Log:
>   Fix a race in vm_page_pagequeue_lockptr().
>
>   The value of m->queue must be cached after comparing it with PQ_NONE,
>   since it may be concurrently changing.
>
>   Reported by:  glebius

What were the symptoms of this issue?  The test plan in the linked
phabricator revision says:

"Gleb reported seeing panics as a result of the use of a bogus index
into the pagequeue array, and also reported that this patch fixed the
panics."

So an attempt to lock pagequeues[PQ_NONE=255].pq_mutex, which is
either something later in the vm_domain object, or bogus memory?  One
of the mtx asserts trips?

Thanks,
Conrad