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 6E63DD7237B for ; Sun, 25 Jan 2026 22:47:45 +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=7by5a2QpHbVkkGG0Gwa33bTUu1MH/K3rRGRtuel9660=; b=hzrpIuvb5pyAVs8D8zSPCaDLdU CiVmkbZFLeJ0N7feriPiJq7UBiMMCKbfse4Mod+fn42h5REVVvjJhcMbVYBBVaHJepswllYAymS6H UuwG5NHBrnvfWrldrUmlGkxd+UJKdKB4CN1V0HQDGI/TVX6J7VTiniVnytni//WfPYVxD1ZDrsmvK +RWy60PcEoRGaykTB4nUYofBTYonoDw/mTsXOdmFKS80O6QEYEHeffHnv3f4bjlc1auejSoaxTBQY U/g55Xhs0p07+Cq0LEnAEeIpTc7ieRoGDdTeMyKPQa0hrC2f+n2ZCNyUU5w25BAtonYzb77bH8dZn +w/lZj2Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vk8tQ-0000000Bc2Q-1ice; Sun, 25 Jan 2026 22:47:40 +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 1vk8tO-0000000Bc0T-1SkE for linux-arm-kernel@lists.infradead.org; Sun, 25 Jan 2026 22:47:38 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id C20A86011E; Sun, 25 Jan 2026 22:47:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AA36C4CEF1; Sun, 25 Jan 2026 22:47:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769381257; bh=wMXJKwwq0CUGfNI5Ih4i6lhiz7gOrxOgiKsZySY9z0I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p61JT54g4toxPnCarvpaFbBjsBbe7y1z48sMSn4GtBKRchfD+DJ6Ktg76jyXqw1QB rOKCvVHN/cqoTXvZZNshucufY4VXA3FM2YoP7ajXUrLgGIEsRmQ8ilZpXbOJVt//Kh NHd7eHilOaEKEtxmiz5uPC9PGvIKQcatLEuwA3+kF8nHRUjAJggboXdirVq/Wz122y rVLgihCncKuJChsc7b2WZT87+bDFo+VCqhKkZUIYeBoDqrIrWZKlWqVn01mGIpDcCI 5cnFi+ABhROKFCwKxe2jKb0e2Yz56ybW7n6Q8jOpO2+5RsvgD2a81S3GiOt0HY23nc s1yjuVMQYNeJw== 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 13/33] sched/isolation: Convert housekeeping cpumasks to rcu pointers Date: Sun, 25 Jan 2026 23:45:20 +0100 Message-ID: <20260125224541.50226-14-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-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 HK_TYPE_DOMAIN's cpumask will soon be made modifiable by cpuset. A synchronization mechanism is then needed to synchronize the updates with the housekeeping cpumask readers. Turn the housekeeping cpumasks into RCU pointers. Once a housekeeping cpumask will be modified, the update side will wait for an RCU grace period and propagate the change to interested subsystem when deemed necessary. Signed-off-by: Frederic Weisbecker --- kernel/sched/isolation.c | 60 +++++++++++++++++++++++++--------------- kernel/sched/sched.h | 1 + 2 files changed, 38 insertions(+), 23 deletions(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 11a623fa6320..6f77289c14c3 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -21,7 +21,7 @@ DEFINE_STATIC_KEY_FALSE(housekeeping_overridden); EXPORT_SYMBOL_GPL(housekeeping_overridden); struct housekeeping { - cpumask_var_t cpumasks[HK_TYPE_MAX]; + struct cpumask __rcu *cpumasks[HK_TYPE_MAX]; unsigned long flags; }; @@ -33,17 +33,28 @@ bool housekeeping_enabled(enum hk_type type) } EXPORT_SYMBOL_GPL(housekeeping_enabled); +const struct cpumask *housekeeping_cpumask(enum hk_type type) +{ + if (static_branch_unlikely(&housekeeping_overridden)) { + if (housekeeping.flags & BIT(type)) { + return rcu_dereference_check(housekeeping.cpumasks[type], 1); + } + } + return cpu_possible_mask; +} +EXPORT_SYMBOL_GPL(housekeeping_cpumask); + int housekeeping_any_cpu(enum hk_type type) { int cpu; if (static_branch_unlikely(&housekeeping_overridden)) { if (housekeeping.flags & BIT(type)) { - cpu = sched_numa_find_closest(housekeeping.cpumasks[type], smp_processor_id()); + cpu = sched_numa_find_closest(housekeeping_cpumask(type), smp_processor_id()); if (cpu < nr_cpu_ids) return cpu; - cpu = cpumask_any_and_distribute(housekeeping.cpumasks[type], cpu_online_mask); + cpu = cpumask_any_and_distribute(housekeeping_cpumask(type), cpu_online_mask); if (likely(cpu < nr_cpu_ids)) return cpu; /* @@ -59,28 +70,18 @@ int housekeeping_any_cpu(enum hk_type type) } EXPORT_SYMBOL_GPL(housekeeping_any_cpu); -const struct cpumask *housekeeping_cpumask(enum hk_type type) -{ - if (static_branch_unlikely(&housekeeping_overridden)) - if (housekeeping.flags & BIT(type)) - return housekeeping.cpumasks[type]; - return cpu_possible_mask; -} -EXPORT_SYMBOL_GPL(housekeeping_cpumask); - void housekeeping_affine(struct task_struct *t, enum hk_type type) { if (static_branch_unlikely(&housekeeping_overridden)) if (housekeeping.flags & BIT(type)) - set_cpus_allowed_ptr(t, housekeeping.cpumasks[type]); + set_cpus_allowed_ptr(t, housekeeping_cpumask(type)); } EXPORT_SYMBOL_GPL(housekeeping_affine); bool housekeeping_test_cpu(int cpu, enum hk_type type) { - if (static_branch_unlikely(&housekeeping_overridden)) - if (housekeeping.flags & BIT(type)) - return cpumask_test_cpu(cpu, housekeeping.cpumasks[type]); + if (static_branch_unlikely(&housekeeping_overridden) && housekeeping.flags & BIT(type)) + return cpumask_test_cpu(cpu, housekeeping_cpumask(type)); return true; } EXPORT_SYMBOL_GPL(housekeeping_test_cpu); @@ -96,20 +97,33 @@ void __init housekeeping_init(void) if (housekeeping.flags & HK_FLAG_KERNEL_NOISE) sched_tick_offload_init(); - + /* + * Realloc with a proper allocator so that any cpumask update + * can indifferently free the old version with kfree(). + */ for_each_set_bit(type, &housekeeping.flags, HK_TYPE_MAX) { + struct cpumask *omask, *nmask = kmalloc(cpumask_size(), GFP_KERNEL); + + if (WARN_ON_ONCE(!nmask)) + return; + + omask = rcu_dereference(housekeeping.cpumasks[type]); + /* We need at least one CPU to handle housekeeping work */ - WARN_ON_ONCE(cpumask_empty(housekeeping.cpumasks[type])); + WARN_ON_ONCE(cpumask_empty(omask)); + cpumask_copy(nmask, omask); + RCU_INIT_POINTER(housekeeping.cpumasks[type], nmask); + memblock_free(omask, cpumask_size()); } } static void __init housekeeping_setup_type(enum hk_type type, cpumask_var_t housekeeping_staging) { + struct cpumask *mask = memblock_alloc_or_panic(cpumask_size(), SMP_CACHE_BYTES); - alloc_bootmem_cpumask_var(&housekeeping.cpumasks[type]); - cpumask_copy(housekeeping.cpumasks[type], - housekeeping_staging); + cpumask_copy(mask, housekeeping_staging); + RCU_INIT_POINTER(housekeeping.cpumasks[type], mask); } static int __init housekeeping_setup(char *str, unsigned long flags) @@ -162,7 +176,7 @@ static int __init housekeeping_setup(char *str, unsigned long flags) for_each_set_bit(type, &iter_flags, HK_TYPE_MAX) { if (!cpumask_equal(housekeeping_staging, - housekeeping.cpumasks[type])) { + housekeeping_cpumask(type))) { pr_warn("Housekeeping: nohz_full= must match isolcpus=\n"); goto free_housekeeping_staging; } @@ -183,7 +197,7 @@ static int __init housekeeping_setup(char *str, unsigned long flags) iter_flags = flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMAIN); first_cpu = (type == HK_TYPE_MAX || !iter_flags) ? 0 : cpumask_first_and_and(cpu_present_mask, - housekeeping_staging, housekeeping.cpumasks[type]); + housekeeping_staging, housekeeping_cpumask(type)); if (first_cpu >= min(nr_cpu_ids, setup_max_cpus)) { pr_warn("Housekeeping: must include one present CPU " "neither in nohz_full= nor in isolcpus=domain, " diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d30cca6870f5..475bdab3b8db 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include -- 2.51.1