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 0FA001F3FED; Wed, 24 Dec 2025 13:47:23 +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=1766584044; cv=none; b=ZGzYHFM5MV4MVut3tCbB64lTP0DREWUMYEE/f7hhmBp9Wt12P9rrIpdSh6A7BgmTEPd9PYnwwMrNNCZpMNXAyVozP7VkAp2BCOki/g6CzX7dVOtEqXWjUbKYiM/d7dhSKxwdqjjrtxIbpzRY69mme+VlwO3yM7T/DQyJ35n5GT8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766584044; c=relaxed/simple; bh=iE5HNXxcf5Yij69saaDAoVPz7iPaTsBAd7fg0JUxZYg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YKsYFOVPmn3IqjVizTJ2V8Q1V5EC0xDH6mwc0zJlE9sEwj+9eQVPzuDDVt0ufeq6VhOXmFI3ZpVYbS3D+YGcd1i+08VCrTUGqsSKvdsuAZnj3efjEUbrWTV3KdVIG4HaukN2Px+9vQ/tA32WC60qqQ1W6i2Eg83iMmI6V6xVzkY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j+0kp3PX; 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="j+0kp3PX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8E31C4CEFB; Wed, 24 Dec 2025 13:47:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766584043; bh=iE5HNXxcf5Yij69saaDAoVPz7iPaTsBAd7fg0JUxZYg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j+0kp3PXfL4fMYcXOUj1cc8tgE/z4aLg9deR40O8qj6JA02pU1GO35D4RicLAQ4z3 Vi9PPvhh57/Lw2GRBZcFeGl6IV0ToE4ficV44TIIEwSp+mjuaydtEFv/h2+AAbVdrk kMaRwxNZeysgzFLOLMU01Wq1dtqjTuYmFpM4UJn69PqDttAd8b20oJBt/n5Ywj760a Fh6r1Am3qgVxLfg7p3yhlJL9sJ0zhrSJcjJoKArtbDYKpaQIVpJ5pjLF1JufFcHOU5 jVbkTQGj1Kc0Ru0HHGaTgzOGYFwdNnRQnX7VIU7ZUtdL3fGLYyTljBCJ8Xn2auSZuA xjPvv5BqhpJDw== 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: Wed, 24 Dec 2025 14:45:00 +0100 Message-ID: <20251224134520.33231-14-frederic@kernel.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251224134520.33231-1-frederic@kernel.org> References: <20251224134520.33231-1-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 11a623fa6320..83be49ec2b06 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 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