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 41FD634DB59; Wed, 5 Nov 2025 21:07:27 +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=1762376848; cv=none; b=gxV8+hCug3ksK/YbMdyDXzjHksgdOGbTMS82TpW9P10q5m8yNfDxDG1E1xsLl9xhS98UxyFt91nmXbh0rAeFvYErXsJPzpNhwg0L9UpzBVNMYZ5AOYJmp7epUZyJARfY6woGaUno7Y6yFIKYFPlYaj+M/RSl9LXY5mOvngszOx4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762376848; c=relaxed/simple; bh=JHjdxV/oITldUpJEMoCsfp/cWcTZCJek1YGVWW127DY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=X9RQi6ht7pvrV/t2jrZrtvy1kuVxgO3O9dE8lpJWWtJJ32iLd/vIemFJsXPPd2cS8Pm0pelFikWUKpfHOv/8odQoeky+LOQRVDGYuN1aAGK4aszb4pF7J6ps/qNda1BrtwIWkE0/c5XP8dxdAfwBFQkti9Mnh8r/fvoinYLV57I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UOtgUGl4; 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="UOtgUGl4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75DB2C116B1; Wed, 5 Nov 2025 21:07:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762376847; bh=JHjdxV/oITldUpJEMoCsfp/cWcTZCJek1YGVWW127DY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UOtgUGl4EzIT/CXtpPARtWFryXQQmWL1KW/pmPm22LHMDdgbfer7GuF7zoHKnxHqD TB4QqR5XgJcd301661MTdPJCcxhHdWwK6+v9/a2D5jrHEcrxFjwsmYvJ69GAjnfSXc JmDP/+paNlSwRUwnoWVwq6PHqKb967VDINvF6ALtLmEl5ZK2M4Ofx/bl9AYMVJH9Rl AFMWTf7iYm9QKnVsrpVA/GIn0bAqNBwkTW1syD35Kawwb9Cd2hde1s5GBOrKRTLdqB /ASLAVCihQZyf2B71XvlxP0975zoCeKrez94TdSXcb1rVwMldhzZmmm9/IIfjVVqZs dlHQCiNEdGKYQ== From: Frederic Weisbecker To: LKML Cc: Gabriele Monaco , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Frederic Weisbecker , 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 26/31] cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping Date: Wed, 5 Nov 2025 22:03:42 +0100 Message-ID: <20251105210348.35256-27-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 From: Gabriele Monaco Currently the user can set up isolated cpus via cpuset and nohz_full in such a way that leaves no housekeeping CPU (i.e. no CPU that is neither domain isolated nor nohz full). This can be a problem for other subsystems (e.g. the timer wheel imgration). Prevent this configuration by blocking any assignation that would cause the union of domain isolated cpus and nohz_full to covers all CPUs. Acked-by: Frederic Weisbecker Reviewed-by: Waiman Long Signed-off-by: Gabriele Monaco Signed-off-by: Frederic Weisbecker --- kernel/cgroup/cpuset.c | 63 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index e19d3375a4ec..d1a799e361c3 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1327,6 +1327,19 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus cpumask_andnot(isolated_cpus, isolated_cpus, xcpus); } +/* + * isolated_cpus_should_update - Returns if the isolated_cpus mask needs update + * @prs: new or old partition_root_state + * @parent: parent cpuset + * Return: true if isolated_cpus needs modification, false otherwise + */ +static bool isolated_cpus_should_update(int prs, struct cpuset *parent) +{ + if (!parent) + parent = &top_cpuset; + return prs != parent->partition_root_state; +} + /* * partition_xcpus_add - Add new exclusive CPUs to partition * @new_prs: new partition_root_state @@ -1391,6 +1404,42 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent, return isolcpus_updated; } +/* + * isolated_cpus_can_update - check for isolated & nohz_full conflicts + * @add_cpus: cpu mask for cpus that are going to be isolated + * @del_cpus: cpu mask for cpus that are no longer isolated, can be NULL + * Return: false if there is conflict, true otherwise + * + * If nohz_full is enabled and we have isolated CPUs, their combination must + * still leave housekeeping CPUs. + */ +static bool isolated_cpus_can_update(struct cpumask *add_cpus, + struct cpumask *del_cpus) +{ + cpumask_var_t full_hk_cpus; + int res = true; + + if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE)) + return true; + + if (del_cpus && cpumask_weight_and(del_cpus, + housekeeping_cpumask(HK_TYPE_KERNEL_NOISE))) + return true; + + if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL)) + return false; + + cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE), + housekeeping_cpumask(HK_TYPE_DOMAIN)); + cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus); + cpumask_and(full_hk_cpus, full_hk_cpus, cpu_active_mask); + if (!cpumask_weight_andnot(full_hk_cpus, add_cpus)) + res = false; + + free_cpumask_var(full_hk_cpus); + return res; +} + static void update_housekeeping_cpumask(bool isolcpus_updated) { int ret; @@ -1538,6 +1587,9 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs, if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) || cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus)) return PERR_INVCPUS; + if (isolated_cpus_should_update(new_prs, NULL) && + !isolated_cpus_can_update(tmp->new_cpus, NULL)) + return PERR_HKEEPING; spin_lock_irq(&callback_lock); isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus); @@ -1637,6 +1689,9 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus, else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) || cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)) cs->prs_err = PERR_NOCPUS; + else if (isolated_cpus_should_update(prs, NULL) && + !isolated_cpus_can_update(tmp->addmask, tmp->delmask)) + cs->prs_err = PERR_HKEEPING; if (cs->prs_err) goto invalidate; } @@ -1984,6 +2039,12 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, return err; } + if (deleting && isolated_cpus_should_update(new_prs, parent) && + !isolated_cpus_can_update(tmp->delmask, tmp->addmask)) { + cs->prs_err = PERR_HKEEPING; + return PERR_HKEEPING; + } + /* * Change the parent's effective_cpus & effective_xcpus (top cpuset * only). @@ -2999,6 +3060,8 @@ static int update_prstate(struct cpuset *cs, int new_prs) * Need to update isolated_cpus. */ isolcpus_updated = true; + if (!isolated_cpus_can_update(cs->effective_xcpus, NULL)) + err = PERR_HKEEPING; } else { /* * Switching back to member is always allowed even if it -- 2.51.0