On Wed, 2016-02-03 at 14:28 -0500, Tejun Heo wrote:
> Hello,
>
> On Wed, Feb 03, 2016 at 08:12:19PM +0100, Thomas Gleixner wrote:
> > > Signed-off-by: Tejun Heo <t...@kernel.org>
> > > Reported-by: Mike Galbraith <umgwanakikb...@gmail.com>
> > > Cc: Tang Chen <tangc...@cn.fujitsu.com>
> > > Cc: Rafael J. Wysocki <raf...@kernel.org>
> > > Cc: Len Brown <len.br...@intel.com>
> > > Cc: sta...@vger.kernel.org # v4.3+
> >
> > 4.3+ ? Hasn't 874bbfe600a6 been backported to older stable kernels?
> >
> > Adding a 'Fixes: 874bbfe600a6 ...' tag is what you really want here.
>
> Oops, you're right. Will add that once Mike confirms the fix.
>
> > > @@ -570,6 +570,16 @@ static struct pool_workqueue
> > > *unbound_pwq_by_node(struct workqueue_struct *wq,
> > > > > > > > > > > > > > > > > > > > > > > > int node)
> > > {
> > > > > > > > > assert_rcu_or_wq_mutex_or_pool_mutex(wq);
> > > +
> > > +> > > > > > /*
> > > +> > > > > > * XXX: @node can be NUMA_NO_NODE if CPU goes offline
> > > while a
> > > +> > > > > > * delayed item is pending. The plan is to keep CPU ->
> > > NODE
> > > +> > > > > > * mapping valid and stable across CPU on/offlines. Once
> > > that
> > > +> > > > > > * happens, this workaround can be removed.
> >
> > So what happens if the complete node is offline?
>
> pool_workqueue lookup itself should be fine as dfl_pwq is assigned to
> all nodes by default. When the node comes back online, things can
> break currently because cpu to node mapping may change. That's what
> Tang has been working on.
That may make confirming the fix a bit problematic. The crash I was
looking at happened on a Fujitsu box.
-Mike
