[PATCH v4 00/12] mm: make userland page table freeing RCU-safe

[Lorenzo Stoakes (ARM)]

On Wed, Sep 23, 2026 at 10:45:33AM +0200, David Hildenbrand (Arm) wrote:
> On 9/23/26 01:00, Andrew Morton wrote:
> > On Tue, 22 Sep 2026 16:35:31 +0100 "Lorenzo Stoakes (ARM)" <ljs at kernel.org> wrote:
> >
> >> The majority of architectures in the kernel defer page table freeing until
> >> an RCU grace period has elapsed, this series converts all remaining
> >> architectures to do so too and eliminates CONFIG_MMU_GATHER_RCU_TABLE_FREE
> >> altogether.
> >>
> >> This is important because it enables safe lockless page table walking under
> >> RCU alone.
> >
> > Do we have reason to believe that anyone is seeing any effects from
> > their arch's failure to rcu-free the page tables?
> >
> > This sounds like a rather long-standing wart, yes?
> >
> > The patchset is thinly reviewed and mm.git is bursting at the seams
> > again.  I'll play wait-and-see on this series.
> Do we want to nudge arch maintainers to review?

(Just to note that I replied separately, 'thinly reviewed' is incorrect, it's
been in -next for weeks and the whole thing was reviewed by Kiryl.)

The only places where that would be useful is m68k motorola, sparc32.

But in any case it has been heavily tested including on every single arch
listed with stress testing performed (I think I cover that in the cover
letter).

The changes are not controversial so I don't think that's a blocker, but
it'd be nice?

>
> --
> Cheers,
>
> David

--
Cheers, Lorenzo