From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7152E5505DA for ; Tue, 22 Sep 2026 23:00:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=172.234.252.31 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790118027; cv=none; b=jbPm9ZJT8sloLLjHByVf+/YsJWGbD9CIGRedTUbUF5aFNW93/VSRJiuO5Ld3zfxFp25WoPn6kNKAmyhEmaY5VRoU0pMbPu24dv0bCYykoFUUvhSF7FMnQc8J0ML5AuppxcQ44syyqatyD2UMlrkMZrml3qhkFFybCUA89GJ6CDA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790118027; c=relaxed/simple; bh=ci3RJD+6cjIcB//FMXtTCbAxugVqCax+YSAYM1WDFm4=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=WJNuWjq8geEGvcCdyIxlYlAueaccM2e58xPqEwTQiTmRMa4pMtoUJirc3VcgyPFzCqcQKMOT4EMvzwnrwHOBScI2cdECZfNRnb2vBmvX98MC3hQQGvM0BXbrZvBP/B6W+hgCoXL6O24J5m8MoFZbiFCtDSrHE9Vje0DCT5ma57w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org; spf=pass smtp.mailfrom=linux-foundation.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=f4enYMEQ; arc=none smtp.client-ip=172.234.252.31 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux-foundation.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="f4enYMEQ" Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 87FC943584; Tue, 22 Sep 2026 23:00:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B2DD81F000FF; Tue, 22 Sep 2026 23:00:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790118024; bh=67Wnb1WqUtfvvqvCH5gthEhN54uXfj3OJmtQ8451vqc=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=f4enYMEQW7QizF7EO1g1cQ4u8gA82wou/SQ/2W3Thvjli+h6aobD5ZlJDs/jfh1FV zSB+Kfk4FuUqyw9bmcvk46t07MCBzK0NBIy1fjrGw3Rhfy7nWNjaUOxIcpoiKWtmMx CWvPp7SZoe+aH84d+5DNVA8gveOr1sRQo2MPtAwc= Date: Tue, 22 Sep 2026 16:00:21 -0700 From: Andrew Morton To: "Lorenzo Stoakes (ARM)" Cc: David Hildenbrand , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Guo Ren , Brian Cain , Geert Uytterhoeven , Dinh Nguyen , Simon Schuster , Jonas Bonn , Stefan Kristiansson , Stafford Horne , Rich Felker , John Paul Adrian Glaubitz , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Russell King , Vineet Gupta , Michal Simek , Chris Zankel , Max Filippov , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , "David S. Miller" , Andreas Larsson , Richard Henderson , Matt Turner , Magnus Lindholm , Catalin Marinas , Mark Rutland , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Richard Weinberger , Anton Ivanov , Johannes Berg , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jason Gunthorpe , John Hubbard , Peter Xu , Yoshinori Sato , Shakeel Butt , Jonathan Corbet , Randy Dunlap , 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-arm-kernel@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 , Qi Zheng , linux-doc@vger.kernel.org Subject: Re: [PATCH v4 00/12] mm: make userland page table freeing RCU-safe Message-Id: <20260922160021.a2fc65d05d9b867a141e5457@linux-foundation.org> In-Reply-To: <20260922-rcu-pagetable-freeing-v4-0-fe1ad1f1e303@kernel.org> References: <20260922-rcu-pagetable-freeing-v4-0-fe1ad1f1e303@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-m68k@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 22 Sep 2026 16:35:31 +0100 "Lorenzo Stoakes (ARM)" 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. Feel free to cluebat me if that's a bad call.