From nobody Sun Feb 8 11:43:10 2026 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 935B730F53E; Sun, 25 Jan 2026 22:47:37 +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=1769381257; cv=none; b=Ou6+gd5CMZWWC5DfaWKoJA7fkFWInpm8+lgtPD4HR89HSuowlMXkX5wbg0lUs/Bm4vzX711sB1VmwMtGKQz+HCn/KaU4QLmHZLONKMyzUwant599ULCR3MVjcJQ2R/8pmBK45znSOoMZ7SiLdMCi4bTvMMzfe5AYCHF6zQNGWeg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769381257; c=relaxed/simple; bh=wMXJKwwq0CUGfNI5Ih4i6lhiz7gOrxOgiKsZySY9z0I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qD++KwQPFyXuW1Iv3cUQ6tWL0YsjsP/cvVWZ59aV0JuL1cyjcG8kZbOp3YelzMWsSRqUFDSZPCVWIgtyxq913VgR5hUt+pexCwg3SAfDLgV//U/5PELg6Os30GHjmckFygDAmiBpYNQ1P+YlM5zxqk3ycwZIPr1iIqjEMcDJIuQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=p61JT54g; 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="p61JT54g" 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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); =20 struct housekeeping { - cpumask_var_t cpumasks[HK_TYPE_MAX]; + struct cpumask __rcu *cpumasks[HK_TYPE_MAX]; unsigned long flags; }; =20 @@ -33,17 +33,28 @@ bool housekeeping_enabled(enum hk_type type) } EXPORT_SYMBOL_GPL(housekeeping_enabled); =20 +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; =20 if (static_branch_unlikely(&housekeeping_overridden)) { if (housekeeping.flags & BIT(type)) { - cpu =3D sched_numa_find_closest(housekeeping.cpumasks[type], smp_proces= sor_id()); + cpu =3D sched_numa_find_closest(housekeeping_cpumask(type), smp_process= or_id()); if (cpu < nr_cpu_ids) return cpu; =20 - cpu =3D cpumask_any_and_distribute(housekeeping.cpumasks[type], cpu_onl= ine_mask); + cpu =3D cpumask_any_and_distribute(housekeeping_cpumask(type), cpu_onli= ne_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); =20 -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); =20 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.flag= s & 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) =20 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 =3D kmalloc(cpumask_size(), GFP_KERNEL); + + if (WARN_ON_ONCE(!nmask)) + return; + + omask =3D 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()); } } =20 static void __init housekeeping_setup_type(enum hk_type type, cpumask_var_t housekeeping_staging) { + struct cpumask *mask =3D memblock_alloc_or_panic(cpumask_size(), SMP_CACH= E_BYTES); =20 - 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); } =20 static int __init housekeeping_setup(char *str, unsigned long flags) @@ -162,7 +176,7 @@ static int __init housekeeping_setup(char *str, unsigne= d long flags) =20 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=3D must match isolcpus=3D\n"); goto free_housekeeping_staging; } @@ -183,7 +197,7 @@ static int __init housekeeping_setup(char *str, unsigne= d long flags) iter_flags =3D flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMAIN); first_cpu =3D (type =3D=3D 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 >=3D min(nr_cpu_ids, setup_max_cpus)) { pr_warn("Housekeeping: must include one present CPU " "neither in nohz_full=3D nor in isolcpus=3Ddomain, " 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 --=20 2.51.1