From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0A55B4BFE90; Thu, 10 Sep 2026 12:09:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789042143; cv=none; b=kpvE8EDRewoWopFxUQ9lvRFM3di/Hfz0FNupYTO98RBldLRgknOgVlMfNjuQnMjGH7pqPg+voKvLIPJsJw+amdn5VMgEFfgJo2ysry7Qi6dwv0PzJY2xLlVJ3y9ZuKYUklQU55FfcPv+AM4NSvfsD/lKvb4osjgv/zLaiEiFp3c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789042143; c=relaxed/simple; bh=+QdmijMIX+OLPq1F9xtXWRLOsn6p6ZPKWz+6/lwS9oc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=B2gCkSHMBqW9PDITLUlutAdF6ssbeldsv930ErsQIBCB/h5ggAwnM0sYAV8EUJEEcfedloKC8Ye7mEA/kTKtPJuPhHGN9k9JiKZrYS79MRsa/bhnvq87j6ZFfaT7GJdP40lQPKEAHV0QF9Uh5WsfbMFxlxg0xSR4VPakI9ZHvKU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R9XvPJax; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R9XvPJax" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E17AD1F00893; Thu, 10 Sep 2026 12:08:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789042141; bh=h8JhehTldcB3FE9LGKhQNq/e+HX2lvut2PpvhgojHPY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=R9XvPJaxnWBT/hhlHZmNBez+Xu7yQO9mAv8dduJTjSJl0gZxISR+BHcwPyiidi1F1 jRKYzFm5oXjvXRnAP6U2pqltMLSl2J8ZQ9WdTNMfl4z61gvUyOWbzyK3Ub4Mw8QuQ/ HFv6DmfgE3cPnMmOo+TKucAGzNXH2GdATJ/t/rZQnGcTM5RCHGS56zOQx045SPfRCx Eh9nVKgokLYia9TMkboW3F9ft5E/ybtN5blbY1wMqkcJStzGzWhQk9A6OS1zAAxuLC C6zxYi09inIeB3Vmv7mraQXhcpNdhDre/6j2qK0OsdoydY771AplJyUt5L0iTDWCpT CjuHp3FDi2xCA== Date: Thu, 10 Sep 2026 14:08:52 +0200 From: "Oscar Salvador (SUSE)" To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , Brendan Jackman , Johannes Weiner , Zi Yan , Oscar Salvador , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Jan Kiszka , Kieran Bingham , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, driver-core@lists.linux.dev, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 08/12] mm/sparse: move __highest_used_section_nr handling Message-ID: References: <20260909-b4-sparsemem_cleanups-v1-0-008fc8d579fe@kernel.org> <20260909-b4-sparsemem_cleanups-v1-8-008fc8d579fe@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Sep 10, 2026 at 11:13:18AM +0200, David Hildenbrand (Arm) wrote: > If you have something consuming __highest_used_section_nr while concurrently > updating it, you might get torn reads/writes that mess up the value on the > reader side. > > For example, mm/compaction.c consuming __highest_used_section_nr. Right, but I guess that if we get a 'wild' value, at least we are guarded by online_section_nr() performing the right thing? Not really figthing anything here, just convincing myself :-) But yes, I guess that we should fix this in case we add more consumers of __highest_used_section_nr in the future. -- Oscar Salvador SUSE Labs