From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BA0C3C43458 for ; Mon, 29 Jun 2026 21:43:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9495A6B00D9; Mon, 29 Jun 2026 17:43:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8FB606B00DB; Mon, 29 Jun 2026 17:43:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C4D16B00DC; Mon, 29 Jun 2026 17:43:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 3DD766B00D9 for ; Mon, 29 Jun 2026 17:43:51 -0400 (EDT) Received: from smtpin07.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id AC9E016704E for ; Mon, 29 Jun 2026 21:43:50 +0000 (UTC) X-FDA: 84934277820.07.4F6C3C6 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf25.hostedemail.com (Postfix) with ESMTP id D8B87A000D for ; Mon, 29 Jun 2026 21:43:48 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=QHSUjjNq; spf=pass (imf25.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782769429; b=s1E/wVAhqUpYCP4mm1gn0dFfdrmAyR4JBHfxivuCKSKRbQPwB9smZlzci0amLEmkAWdF6T TUXZ6SNONtVZPffyUger9xr6c0KzsnogDN+V+on27PPL/CNZGxI2SzvygcuSWw0FpkQyx/ +qJ+dFfE16XCZjdoO8BgkeP1oM6m26M= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782769429; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Qaq/l48Qg4gbR4mCxjR4xD4x8eYI85JxPO6iTE5dUPU=; b=cCg/1AYCXwBKear0wI5a2hpm2lpY1xjSDjfy3louyfEzqoyam+KmQnOSheuFM7yTS6r2YC H0Sp+X7JSsGtSyQXhL8D0Nvjh1e+5pqQVnSj2KP/hsW3/upBwWyfvbftPgLJh8udPotaQx 1saCHz5mRJrELBJDz24zBakbokf97bU= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=QHSUjjNq; spf=pass (imf25.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C82F7408BD; Mon, 29 Jun 2026 21:43:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7E541F000E9; Mon, 29 Jun 2026 21:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782769427; bh=Qaq/l48Qg4gbR4mCxjR4xD4x8eYI85JxPO6iTE5dUPU=; h=Date:Subject:From:To:Cc:References:In-Reply-To; b=QHSUjjNq2QpStLa3GD6vl4jBsKzSmS/f8FfZfisfRKtOzuL8WHt31yfrKovezylrV UHtHGxR68i6JLUy5kS1QDnE3BdcJHAWj2IclDKFi4/o5DhnvILY1oqXtTiH6JIFDcq 5rrc0gG5aF2WIQuKUZMc7AALRZPyWCD89Ud8mclI+iS+0Yryru6qKY7Yk3L098LIO/ szaUqa6PCQOPHbiySzM1X+4jz7ZxUp1QbbEVNHStxqUDPIYzNe4V6kkP3RRbGtsSaT Memvf+g8UD3j5HiCkfykoEygeiItdjZbW1acNoIKGOriOASvINRoFR25X5ln7N7D/I e1y0YeP8AZtdA== Message-ID: <0a309ed3-378e-4d88-95a0-65bf47c5496d@kernel.org> Date: Mon, 29 Jun 2026 23:43:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] mm: memory-failure: fix HWPoison flag race with non-atomic page flag ops From: "David Hildenbrand (Arm)" To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Miaohe Lin , Naoya Horiguchi , Andrew Morton , Oscar Salvador , Andi Kleen , Hidehiro Kawai , Rik van Riel , Vlastimil Babka , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Hao Li , Kiryl Shutsemau , Byungchul Park , linux-mm@kvack.org, linux-cxl@vger.kernel.org References: <0b5f8b4b-d7dc-4b79-9555-a5b36265f3a9@kernel.org> <20260629030657-mutt-send-email-mst@kernel.org> <4f5ba5d6-246c-4430-9737-e8dd8e4c5142@kernel.org> <20260629092856-mutt-send-email-mst@kernel.org> <54c8cbee-9b26-458c-93ba-5aa594f5d1e8@kernel.org> Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <54c8cbee-9b26-458c-93ba-5aa594f5d1e8@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: iw136e3cqj1os31n8e3otigs34yjhzzk X-Rspamd-Queue-Id: D8B87A000D X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1782769428-10339 X-HE-Meta: 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 u1XjreIm ZFAS+HbReLb2toYm0D1cXl0rA4YlI9BTqIoT9FjlkKIVxxoA5JJMU69qNIu4yYFTVrlOCJD69O0Zm7F7yJJgbQa7xNhB21GHC4fmTSct2ETdQQPhZmM5ejbEB1pZV4fQHG2WV3wwaYdgG1oJPWwhHVqgAk/GWO/SlZCwHDEbDN92mnbz3zM9Wl234FtBXUykHQYVUWuOQR5siZcilVaQ7gZpq2j0zKIZBZVw/yU0q5JFscV4tdgSYJgeqdTDoLiQIT5GbkIryL3Pb1nQlvJkaKDTRTQaNnu8C1/iJFBebSajjk4DtsVubzZwsNr+9ARBY/+OxEUYyW7u0A6srXbKRkNVVOg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/29/26 23:22, David Hildenbrand (Arm) wrote: > [...] > >> >> And again, I'm really not sure fixing a theoretical race when memory >> is failing is worth slowing the world by 0.1-1% for. >> > > Fully agreed. I was hoping RCU was cheaper (I mean, we were once told that RCU > read side locking is essentially for free ... well in some configs :) ) > > The question if we could optimize it reasonably enough ... > >> >> From what I saw in my testing, if we allocate 4k pages >> it's hidden by the overhead. With hp and thp it's measureably >> worse than rcu on !preempt config. > > ... for example, by doing the rcu read lock + unlock around the > > for (i = 1; i < (1 << order); i++) { > > loop on the alloc path. But I suspect it's not going to make that much of a > difference. > > I concluded, similar to Andi, that stop_machine() is too big of a hammer. > > I wonder if something could be built out of preempt_disable() and sync SMP > calls. hmm :( Scrap that, shouldn't work I think ... -- Cheers, David