From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 78AB434D4E1; Wed, 5 Nov 2025 21:06:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762376816; cv=none; b=FbE/uDVH9p3z3OvyV9c1CBFdZ9I7U8EupxH0LI0KwEzFwnjHM3+YAgyPNBlZmaEAugokJtnq1rKDN5azFA+qMXGY4IKfvmfsjLNkZK5eB3KnbxgwQSrdS1HgSqbOFNf2BRAxZU5SvxOa/5pPrYu0VdmfNy308/lQua9buu383vU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762376816; c=relaxed/simple; bh=rc90r/VJRIFUeghTYji80GjIJHgeRfSLzAtAWtKNZdY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Td9iluG47f5twEtCRnu041Aj6TOxZPkhjNkUsMkS1jDkQqZJwOhnE81btX9q8zVQwgrLIs6yMLFnf74FxKVZ8pXp7jkDw86o5UyQAyRbzNmcBNEOUvYH7Js2TjQEIGEcHnpsxsTPP+JGSl1FUV1mc6BY+XzzQaa/YE1ppUIiAKo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hz7xihx1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hz7xihx1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 918F2C116B1; Wed, 5 Nov 2025 21:06:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762376816; bh=rc90r/VJRIFUeghTYji80GjIJHgeRfSLzAtAWtKNZdY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hz7xihx1glmCXa1xYOTXCOtZCwF0OTEG4MDXz4ESiFKIT/eSzyLgw6tdM/A/8ArrJ IEd6sw+KI8CCzzGQUHk4lbghlqPOFoH0V+bJWqxwNfBrriit2+q0O9a/xMKNAVftG1 pdEtz6CY10kisa6Dvp3UjaeNE1tQMLiHK0nc3QJKfijSBQW1LtHsUNCwdyFZvY3JRx 30ZUh5GLz8QEnuL2xArNJEP1+nfwTiM+E7KRZVU84r9zqRWV8rANivY1p/SX18pPk8 Q13aJlDvbtRaohmyRA5PXJR2bE/8UKI4+NRSo21D37HRxvequjK1Me/ZODpo/5OSaB S5lgY0KgQyIzw== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , 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 22/31] kthread: Include unbound kthreads in the managed affinity list Date: Wed, 5 Nov 2025 22:03:38 +0100 Message-ID: <20251105210348.35256-23-frederic@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251105210348.35256-1-frederic@kernel.org> References: <20251105210348.35256-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- kernel/kthread.c | 70 ++++++++++++++++++++++++++++-------------------- 1 file changed, 41 insertions(+), 29 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index c4dd967e9e9c..b4794241420f 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) @@ -924,8 +922,22 @@ 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); -- 2.51.0