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

From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: "David Hildenbrand (Arm)" <david@kernel.org>,
	 Andrew Morton <akpm@linux-foundation.org>,
	Zi Yan <ziy@nvidia.com>,
	 Baolin Wang <baolin.wang@linux.alibaba.com>,
	"Liam R. Howlett" <liam@infradead.org>,
	 Nico Pache <nico.pache@linux.dev>,
	Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
	 Barry Song <baohua@kernel.org>,
	Lance Yang <lance.yang@linux.dev>,
	 Usama Arif <usama.arif@linux.dev>,
	Kiryl Shutsemau <kas@kernel.org>, Guo Ren <guoren@kernel.org>,
	 Brian Cain <bcain@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	 Dinh Nguyen <dinguyen@kernel.org>,
	Simon Schuster <schuster.simon@siemens-energy.com>,
	 Jonas Bonn <jonas@southpole.se>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	 Stafford Horne <shorne@gmail.com>, Rich Felker <dalias@libc.org>,
	 John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	Paul Walmsley <pjw@kernel.org>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Alexandre Ghiti <alex@ghiti.fr>,
	Russell King <linux@armlinux.org.uk>,
	 Vineet Gupta <vgupta@kernel.org>,
	Michal Simek <monstr@monstr.eu>, Chris Zankel <chris@zankel.net>,
	 Max Filippov <jcmvbkbc@gmail.com>, Will Deacon <will@kernel.org>,
	 "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
	Nick Piggin <npiggin@gmail.com>,
	 Peter Zijlstra <peterz@infradead.org>,
	"David S. Miller" <davem@davemloft.net>,
	 Andreas Larsson <andreas@gaisler.com>,
	Richard Henderson <richard.henderson@linaro.org>,
	 Matt Turner <mattst88@gmail.com>,
	Magnus Lindholm <linmag7@gmail.com>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	 Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	 Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	 Helge Deller <deller@gmx.de>,
	Madhavan Srinivasan <maddy@linux.ibm.com>,
	 Michael Ellerman <mpe@ellerman.id.au>,
	"Christophe Leroy (CS GROUP)" <chleroy@kernel.org>,
	 Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	 Alexander Gordeev <agordeev@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	 Sven Schnelle <svens@linux.ibm.com>,
	Richard Weinberger <richard@nod.at>,
	 Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	 Thomas Gleixner <tglx@kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	 Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	 Arnd Bergmann <arnd@arndb.de>, Mike Rapoport <rppt@kernel.org>,
	 Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>, Jason Gunthorpe <jgg@ziepe.ca>,
	 John Hubbard <jhubbard@nvidia.com>, Peter Xu <peterx@redhat.com>,
	 Yoshinori Sato <ysato@users.sourceforge.jp>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	 Jonathan Corbet <corbet@lwn.net>,
	Randy Dunlap <rdunlap@infradead.org>,
	linux-mm@kvack.org,  linux-kernel@vger.kernel.org,
	linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,
	 linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org,
	linux-sh@vger.kernel.org,  linux-riscv@lists.infradead.org,
	linux-snps-arc@lists.infradead.org, linux-arch@vger.kernel.org,
	 sparclinux@vger.kernel.org, linux-alpha@vger.kernel.org,
	loongarch@lists.linux.dev,  linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	 linux-s390@vger.kernel.org, linux-um@lists.infradead.org,
	Hugh Dickins <hughd@google.com>,  Qi Zheng <qi.zheng@linux.dev>,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH v4 00/12] mm: make userland page table freeing RCU-safe
Date: Wed, 23 Sep 2026 12:39:41 +0100	[thread overview]
Message-ID: <arO6UpHLChZqAjBm@gremlin> (raw)
In-Reply-To: <300f92ef-1526-44d9-a01f-e9b8f3fc0cd1@kernel.org>

On Wed, Sep 23, 2026 at 11:39:27AM +0200, Vlastimil Babka (SUSE) wrote:
> On 9/23/26 11:15, David Hildenbrand (Arm) wrote:
> > On 9/23/26 11:04, Lorenzo Stoakes (ARM) wrote:
> >> On Wed, Sep 23, 2026 at 10:45:33AM +0200, David Hildenbrand (Arm) wrote:
> >>> On 9/23/26 01:00, Andrew Morton wrote:
> >>>>
> >>>>
> >>>> 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.)
> >
> > Ack.
> >
> >>
> >> 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?
> >
> > I doubt we'll ever get sparc32 reviews :)
> >
> > I'd definitely appreciate some review on the arch bits from arch maintainers,
> > but if they don't reply within the next weeks I wouldn't wait on that.
>
> Indeed, for minor arches like this the lack of review (it would be a whole
> cycle by the merge window) shouldn't be a blocker for important tree-wide
> progress.

Thanks appreciated!

Greg from m68k has had a look so seems we have movement there anyway! :)

--
Cheers, Lorenzo