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 C7420D7237B for ; Sun, 25 Jan 2026 22:49:24 +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=neU0GC3bglMYYBWUhbgBncqUt1 Nz6fIFIjDxBrW5K783SYTfOsf5DHY4ww2WNfUL2QWBOagSRwphSbfnhFJ22phWtNAHwiYKnbp74dX /2Yi5Q2pwtIcvr+9W85U4NB4ZddzFllU2CGEDK3b3Ngjfmm8oaPySh1TK9VyIpOj5ZblYgU3eEEUT zzHmr11l2hfW+g/Tegro+92P3VIC5wVqSJPFn2f8ZbOm30+2dQc6JXkqqg1/eqGGPKqD1sJ95eXpO qW0GCAj3L39UcF3DI8Hk4GQcVMAJ5KOBoc9DowZdxOb0J1Oa51kTU07aFO6WnEAO+QYLmrt+XrCgQ bHoD8r8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vk8v0-0000000BdEN-2nO3; Sun, 25 Jan 2026 22:49:18 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vk8uy-0000000BdBV-0ulu for linux-arm-kernel@lists.infradead.org; Sun, 25 Jan 2026 22:49:17 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id E1881443D8; Sun, 25 Jan 2026 22:49:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1ECDC2BC87; Sun, 25 Jan 2026 22:49:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769381355; bh=FQiUYX134QuRdMK2UHqgCPVDFLi7Mj4zGAJtAEtu0Bs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UgViSQhGT3Wuke/Yit+vSr4vsPQsGUB9TksMilPkbw8ucPH88dnfcU8EQRgMLb06e lN2gyJnxemaInoGQz3B75xDql7Evl1TQQ4zZmMsXAnbD1Urr7NwOnt6wOnaYCOQeeQ sgfXCryqqyMrpzQwx8K3coFYao2XKspATR/APoqQUbITIoNDoEi47ehdm2MK1mENnZ ywxEht8+8pss3W8QMkb/rQLYybf1dBhLQUt9LxeRxUkMJZvTICvHfAVqI24kffYkw6 adk3FM+FdCMT9PgkO4j8TJQKImvmwOStO+j50JTiTr4NKwPRgOc7x/stxI36amWxYC ikhAsOpNxxM2A== 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: Sun, 25 Jan 2026 23:45:32 +0100 Message-ID: <20260125224541.50226-26-frederic@kernel.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20260125224541.50226-1-frederic@kernel.org> References: <20260125224541.50226-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260125_144916_338632_AB3BC6C9 X-CRM114-Status: GOOD ( 18.61 ) 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