Re: [PATCH v3] mm: fix tick timer stall during deferred page init

[Pavel Tatashin]

On Wed, Apr 1, 2020 at 12:26 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>
> On Wed 01-04-20 12:18:10, Daniel Jordan wrote:
> > On Wed, Apr 01, 2020 at 06:12:43PM +0200, Michal Hocko wrote:
> > > On Wed 01-04-20 12:09:29, Daniel Jordan wrote:
> > > > On Wed, Apr 01, 2020 at 06:00:48PM +0200, Michal Hocko wrote:
> > > > > On Wed 01-04-20 17:50:22, David Hildenbrand wrote:
> > > > > > On 01.04.20 17:42, Michal Hocko wrote:
> > > > > > > This needs a double checking but I strongly believe that the lock can be
> > > > > > > simply dropped in this path.
> > > >
> > > > This is what my fix does, it limits the time the resize lock is held.
> > >
> > > Just remove it from the deferred intialization and add a comment that we
> > > deliberately not taking the lock here because abc
> >
> > I think it has to be a little more involved because of the window where
> > interrupts might allocate during deferred init, as Vlastimil pointed out a few
> > years ago when the change was made.
>
> I do not remember any details but do we have any actual real allocation
> failure or was this mostly a theoretical concern. Vlastimil? For your
> context we are talking about 3a2d7fa8a3d5 ("mm: disable interrupts while
> initializing deferred pages")

I do not remember seeing any real failures, this was a theoretical
window. So, we could potentially simply remove these locks until we
see a real boot failure in some interrupt thread. The allocation has
to be rather large as well.

Pasha