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 4AC3C34DB78; Wed, 5 Nov 2025 21:05:37 +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=1762376738; cv=none; b=RE+VAJ0l2+bf756uLzWD0BZVywvO9/ZS48xMwxtuQFG0PL1Vgpk5IF3HSY+SV3M0X2Ef6m5ERHcr6IlTd0M7FOkJe8dYFqA9sGy6h6MpN9yVlQfXr96GTZBpTd5ku5zDgaV9ffAyz/Tl3jNXh42dXZIF3vBji7Vbq9RYMEbq2lM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762376738; c=relaxed/simple; bh=ZZ+yP0oE5nMuQO76ubRYWghmJmjtLp6J4+mGRrvjt9Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CAqS9LOpefzj2vGVPvchia5p+wcARp9R62JOqQ6xULlKxyEwE2BEXno2Hk5oQbsjwo8pV58X4XdPpMZqAwdl9IHIsWEJzDlR5b6sUlkTEZ4AbwUpk2Ro7i3Zp8PMYTOPm3vD9x2+82uWJcQDu7BpPA0/FHPdjsc++q5m+66D6MU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iz1hWSwd; 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="iz1hWSwd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AEAC4C16AAE; Wed, 5 Nov 2025 21:05:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762376736; bh=ZZ+yP0oE5nMuQO76ubRYWghmJmjtLp6J4+mGRrvjt9Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iz1hWSwdNKtj6UL9xcFuZBN1Kztkumf9wbEcmW5UjeJ2+UdL5tz673c7YJbvnt7/W c/EsY/6qjrORrgn3JfyeSAFSA6yfuYj5MTyOVvQkADRrio6BIJnZRu8YgpBrNgVOTQ eB/pL0KTpvOBNIGNkXD26pikUAULqAaaEwLWkA8jIkjfsA7l7XWyC38MgQB4N6su+k xJuzdIt/BEh9tFL8ETLq2lHz2UCG4Z9ajVxdFB5FH9oWQbaVglAAEfr62yb7elqNOG NuaQirecRskVf5fcOpqOIlmu+m4oVCOMYMKsiFs1KZvDxh3o6NbGgk4qDg0Xqhox9y ldKy71009PlQQ== 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 12/31] sched/isolation: Convert housekeeping cpumasks to rcu pointers Date: Wed, 5 Nov 2025 22:03:28 +0100 Message-ID: <20251105210348.35256-13-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: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 | 58 +++++++++++++++++++++++++--------------- kernel/sched/sched.h | 1 + 2 files changed, 37 insertions(+), 22 deletions(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 8690fb705089..bee6c04be103 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; } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index adfb6e3409d7..2fc1ddde3120 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include -- 2.51.0