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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D6A4AEEEC1C for ; Thu, 1 Jan 2026 22:18:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Qz+DGGx2ncZ3Mxc9/jgxTMCGdzAmp3ATkT9oSs7t3lw=; b=ILup5qmft77U+dkGgLzc9WnZK3 vC9eP/Nk9jxXPXGnilLDw5tj8uEkYFnMA+OFQYqusmcHIPQQUJ79b7GdUIrzmbESPQslliq/Lr1kI miTrtv4gIzG8xJMT+uQvbTMOPxwu5Zxx4fU87VaqNPFknvcFGRGtqMqgq/e4V5ZXh32trvRNflNrH 0095IFqrUiiCg/Vp/oKeR2MDnUDz5AfKOW/TTLAECrEBhMIPKSn5SyhkUYdfgdyKJ5GrbWtdwt2YI MHBBWtxrVq4+LMGn0m3fhGAveMKQg5EHyLQdJsuO+2okML1V1CRW6dyqUm2AuVVbRlUJ+ndd9Tyc+ 0k78e2vQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vbQzM-00000007ZIu-2E25; Thu, 01 Jan 2026 22:17:48 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vbQzD-00000007ZAv-0lEz for linux-arm-kernel@lists.infradead.org; Thu, 01 Jan 2026 22:17:42 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 890D660054; Thu, 1 Jan 2026 22:17:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE941C4CEF7; Thu, 1 Jan 2026 22:17:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767305858; bh=FQiUYX134QuRdMK2UHqgCPVDFLi7Mj4zGAJtAEtu0Bs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XUUyVasV1u3U2OAhlAsfAFSvZ4/84T9b+/Yagnb//7l06XW+pfb5SupHsl14EiZpO A7lsNvE8Gz+f+oav882CaJu+Xr395Aa7paTMq2wgWOtR+SCJ7KEkBgm/Nqga2j78Uv n0MCp/pybncPc+ax+ldjdWVCiUZtymea0X7ESH0dyW5NSBWCHbzy4fDnSkNN0RchSd 9li0iyITeAlfDOmRXA/n5dUyWiFv4oc1wW0hluBRrDSwHC9VV3yDZGdZ3gy3FS4xaB r1/38N02msJBlnvE+rPs8/2v5u9pgbKK9m+UOQpt8txpDDJyrkxcvJloMMe3jpoqJf D1of5SnkyyUJA== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Chen Ridong , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH 25/33] kthread: Include unbound kthreads in the managed affinity list Date: Thu, 1 Jan 2026 23:13:50 +0100 Message-ID: <20260101221359.22298-26-frederic@kernel.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20260101221359.22298-1-frederic@kernel.org> References: <20260101221359.22298-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The managed affinity list currently contains only unbound kthreads that have affinity preferences. Unbound kthreads globally affine by default are outside of the list because their affinity is automatically managed by the scheduler (through the fallback housekeeping mask) and by cpuset. However in order to preserve the preferred affinity of kthreads, cpuset will delegate the isolated partition update propagation to the housekeeping and kthread code. Prepare for that with including all unbound kthreads in the managed affinity list. Signed-off-by: Frederic Weisbecker Reviewed-by: Waiman Long --- kernel/kthread.c | 70 ++++++++++++++++++++++++++++-------------------- 1 file changed, 41 insertions(+), 29 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index f1e4f1f35cae..51c0908d3d02 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -365,9 +365,10 @@ static void kthread_fetch_affinity(struct kthread *kthread, struct cpumask *cpum if (kthread->preferred_affinity) { pref = kthread->preferred_affinity; } else { - if (WARN_ON_ONCE(kthread->node == NUMA_NO_NODE)) - return; - pref = cpumask_of_node(kthread->node); + if (kthread->node == NUMA_NO_NODE) + pref = housekeeping_cpumask(HK_TYPE_KTHREAD); + else + pref = cpumask_of_node(kthread->node); } cpumask_and(cpumask, pref, housekeeping_cpumask(HK_TYPE_KTHREAD)); @@ -380,32 +381,29 @@ static void kthread_affine_node(void) struct kthread *kthread = to_kthread(current); cpumask_var_t affinity; - WARN_ON_ONCE(kthread_is_per_cpu(current)); + if (WARN_ON_ONCE(kthread_is_per_cpu(current))) + return; - if (kthread->node == NUMA_NO_NODE) { - housekeeping_affine(current, HK_TYPE_KTHREAD); - } else { - if (!zalloc_cpumask_var(&affinity, GFP_KERNEL)) { - WARN_ON_ONCE(1); - return; - } - - mutex_lock(&kthread_affinity_lock); - WARN_ON_ONCE(!list_empty(&kthread->affinity_node)); - list_add_tail(&kthread->affinity_node, &kthread_affinity_list); - /* - * The node cpumask is racy when read from kthread() but: - * - a racing CPU going down will either fail on the subsequent - * call to set_cpus_allowed_ptr() or be migrated to housekeepers - * afterwards by the scheduler. - * - a racing CPU going up will be handled by kthreads_online_cpu() - */ - kthread_fetch_affinity(kthread, affinity); - set_cpus_allowed_ptr(current, affinity); - mutex_unlock(&kthread_affinity_lock); - - free_cpumask_var(affinity); + if (!zalloc_cpumask_var(&affinity, GFP_KERNEL)) { + WARN_ON_ONCE(1); + return; } + + mutex_lock(&kthread_affinity_lock); + WARN_ON_ONCE(!list_empty(&kthread->affinity_node)); + list_add_tail(&kthread->affinity_node, &kthread_affinity_list); + /* + * The node cpumask is racy when read from kthread() but: + * - a racing CPU going down will either fail on the subsequent + * call to set_cpus_allowed_ptr() or be migrated to housekeepers + * afterwards by the scheduler. + * - a racing CPU going up will be handled by kthreads_online_cpu() + */ + kthread_fetch_affinity(kthread, affinity); + set_cpus_allowed_ptr(current, affinity); + mutex_unlock(&kthread_affinity_lock); + + free_cpumask_var(affinity); } static int kthread(void *_create) @@ -919,8 +917,22 @@ static int kthreads_online_cpu(unsigned int cpu) ret = -EINVAL; continue; } - kthread_fetch_affinity(k, affinity); - set_cpus_allowed_ptr(k->task, affinity); + + /* + * Unbound kthreads without preferred affinity are already affine + * to housekeeping, whether those CPUs are online or not. So no need + * to handle newly online CPUs for them. + * + * But kthreads with a preferred affinity or node are different: + * if none of their preferred CPUs are online and part of + * housekeeping at the same time, they must be affine to housekeeping. + * But as soon as one of their preferred CPU becomes online, they must + * be affine to them. + */ + if (k->preferred_affinity || k->node != NUMA_NO_NODE) { + kthread_fetch_affinity(k, affinity); + set_cpus_allowed_ptr(k->task, affinity); + } } free_cpumask_var(affinity); -- 2.51.1