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 71C19343213; Fri, 29 Aug 2025 15:49:33 +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=1756482573; cv=none; b=ckj5ETJTY8bzPxhc6/uwG1eMGlMkM1P4GPDQE8vbwn5gL79ZqxSWRtcr+XD9zx6RZTvWXBg/YassXW65wFdPU8uIlD0KcmWfJHhJ967fXdt5WIZRbWbILNxctosFM4fAOqg8zngh01w/vbVTpnR3TGcxZaP3r3mKOvOGRnfyhTE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756482573; c=relaxed/simple; bh=EmolSYetz1s/vfgGS0udWvK8bCbBeW5BQ9rcUHulJgU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=azgr67X4FhVxRy7RiszL1C6B/K0yo9J2rsNESX5s/SW8kr8PrhvbsTIuSckCSxgFw6fMwoWn+ETNfAWDDP+vL1JArUs/qYKZoRl54EJ5cq1sAzz1TLJtn5cVuTZa0qQcsXCx3ygEWVlWP+csWFwU63KCsiPV9SpmlCeQ5BRaWPU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=X/pUjtlN; 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="X/pUjtlN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BA13C4CEF5; Fri, 29 Aug 2025 15:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756482573; bh=EmolSYetz1s/vfgGS0udWvK8bCbBeW5BQ9rcUHulJgU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=X/pUjtlNA3q8T67DkXk64bvz6y4vf1gZ6dHbOkQSJuTI4OF6qrBqu5Azg6hPuGhFm u3YuLghkohNMiRlCWgTxFPn+r7RzhNeUwsX0DPcfpy1DdOwQd7MovxWTkwJ4PlBVnT QFFD1nUfxfhqp/BE2iFnFd0sxdqvXSC2SGI0VyF9fqvD+5kBx4kqStNdTT4HeCTKPh LZIrbLMvl/ZXJnLXM/Ek1PZ4ioC5muDBFSob5aphSZM6Itx38A5pdFvsvqV/omLn/I IQqUr5C2LEXVwhoAxB1qRTVza99aUGghEmAXVK6MjNsSQPDxkwVocHc7TEPuDKgpVg WNwn2SD2W3XHQ== From: Frederic Weisbecker To: LKML Cc: Gabriele Monaco , Johannes Weiner , Marco Crivellari , Michal Hocko , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Peter Zijlstra , Tejun Heo , Thomas Gleixner , Waiman Long , cgroups@vger.kernel.org, Frederic Weisbecker Subject: [PATCH 26/33] cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping Date: Fri, 29 Aug 2025 17:48:07 +0200 Message-ID: <20250829154814.47015-27-frederic@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250829154814.47015-1-frederic@kernel.org> References: <20250829154814.47015-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 Signed-off-by: Gabriele Monaco Signed-off-by: Frederic Weisbecker --- kernel/cgroup/cpuset.c | 57 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index df1dfacf5f9d..8260dd699fd8 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1275,6 +1275,19 @@ 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 @@ -1339,6 +1352,36 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent, return isolcpus_updated; } +/* + * isolcpus_nohz_conflict - check for isolated & nohz_full conflicts + * @new_cpus: cpu mask for cpus that are going to be isolated + * Return: true if there is conflict, false otherwise + * + * If nohz_full is enabled and we have isolated CPUs, their combination must + * still leave housekeeping CPUs. + */ +static bool isolcpus_nohz_conflict(struct cpumask *new_cpus) +{ + cpumask_var_t full_hk_cpus; + int res = false; + + if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE)) + return false; + + if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL)) + return true; + + 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_online_mask); + if (!cpumask_weight_andnot(full_hk_cpus, new_cpus)) + res = true; + + free_cpumask_var(full_hk_cpus); + return res; +} + static void update_housekeeping_cpumask(bool isolcpus_updated) { int ret; @@ -1453,6 +1496,9 @@ 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) && + isolcpus_nohz_conflict(tmp->new_cpus)) + return PERR_HKEEPING; spin_lock_irq(&callback_lock); isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus); @@ -1552,6 +1598,9 @@ 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) && + isolcpus_nohz_conflict(tmp->addmask)) + cs->prs_err = PERR_HKEEPING; if (cs->prs_err) goto invalidate; } @@ -1904,6 +1953,12 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, return err; } + if (deleting && isolated_cpus_should_update(new_prs, parent) && + isolcpus_nohz_conflict(tmp->delmask)) { + cs->prs_err = PERR_HKEEPING; + return PERR_HKEEPING; + } + /* * Change the parent's effective_cpus & effective_xcpus (top cpuset * only). @@ -2924,6 +2979,8 @@ static int update_prstate(struct cpuset *cs, int new_prs) * Need to update isolated_cpus. */ isolcpus_updated = true; + if (isolcpus_nohz_conflict(cs->effective_xcpus)) + err = PERR_HKEEPING; } else { /* * Switching back to member is always allowed even if it -- 2.51.0