From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.147 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794453591; b=Kx/5ErNcgUaFwQfKXe3hxAAd9+4thjXGDVsivzlBlYQXDFu1v1ey/pXeupzjvRYGEpYL qVbn6X9GLB2qGSLNE8T7wGVToIZoP2NCKxH8JmQyCoMT0xPaHDoZd4LqBPra5fC9rcbt6 VfBN44dIdseo2+QufPpLqZs/eObKltfNSguAofFe21v6pszld6DBYvZETcb8tAO/mujcw n77hNu0r1gmuw/VBu6p7jvrzaVklah+iDHCyLwpObfJh4txwCG35dgwSfj3tFDRPlCGsW RUBLscCGWR8Qk+vSt9ugp3x1ErKX4h+BW74J/dy+CFhVskiWxVZlcM3B7IbYS8t0+Tg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794453591; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-Id: X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=nvUZ34nPxZazwlTbD/8PsuETHVUvr3C/ri4cQ71QSpw=; b=Jo55ZRIw0AOMw1gyoKUJCkwT2mZTorw6ru64xCyartk4R6jcmBUGFKpl/3pxRSTGgXJt 8Kiar3BqTp/KnNNDqBpXVNMRfKRJuxfXgCsXtzDOQTc0MFwJwDZQReEUPHsNgebO9wLa9 gZqDEUZkUoOuXoX0gWBazV5jRoW3YUftEGJn0nWIon8q/+cItGs+TwPHfJsgCnhqh4Vxk W9UQJNwqbY4jevq3Rm6SHipUXcw+nliWC0K4K8Hc5IoZeRWWdOVBE1JTLnIdMb3staY3F v6t29e2lWcQ9UWFsK3bi5Q5VpRvtVWepMF0VGFTZWkSXCfphmh5qnG73eePdRPARE5Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=Wcd+OcGL; arc=none smtp.remote-ip=91.218.175.147 Received: from mta0.migadu.com (out-147.mta0.migadu.com [91.218.175.147]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A5C7606A33B for ; Thu, 12 Nov 2026 03:19:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 2A5C7606A33B Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=Wcd+OcGL X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=y1rD3PoK2TZr83Gmj3bPRPvTiuuUx5VKCCC9EHCyIZM=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794453588; v=1; x=1795058388; b=Wcd+OcGLTOx5w+FydobYkvUjXvt8ldh8GxbfPRG7oPK/d1am+3DFfZXXewkxooBlwwdd3tvx hVklkrJqgcex8ue986eqHIprSnXhWvWZ6bXao5mj5KbocpL/yzy+SSGW6anns5DaENV1KDRT4Tx ASKKl1xhmi95xYQ5WM+bSCow= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 1a56a09c29a54ed5; Thu, 12 Nov 2026 03:19:48 +0000 X-Mizu-Trace-ID: 1a56a09c29a54ed5 X-Migadu-Flow: FLOW_OUT From: Ridong Chen To: Waiman Long , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Shuah Khan Cc: Ridong Chen , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Guopeng Zhang , Ridong Chen Subject: [PATCH for-7.4-fixes v4 1/2] cpuset: settle isolation state when CPUs are given back to parent Date: Thu, 12 Nov 2026 11:19:30 +0800 Message-Id: <20261112031931.2815548-2-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261112031931.2815548-1-ridong.chen@linux.dev> References: <20261112031931.2815548-1-ridong.chen@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ridong Chen partition_xcpus_del() only updates isolated_cpus when the partition that gives back the CPUs has a different state than its parent. CPUs that were further distributed to descendant isolated partitions are not taken into account, so isolated_cpus_release() has to be called afterwards in several places to walk up the ancestors and fix isolated_cpus. This misses some cases and leaks isolated CPUs, as reported by Guopeng. An isolated partition can be invalidated after its parent has already become invalid, and its CPUs are left in isolated_cpus. For example, on a 32-CPU system with all CPUs online and without isolcpus= or nohz_full= boot parameters: cd /sys/fs/cgroup echo +cpuset > cgroup.subtree_control mkdir A echo 0,2-31 > A/cpuset.cpus echo root > A/cpuset.cpus.partition echo +cpuset > A/cgroup.subtree_control mkdir A/B echo 2-3 > A/B/cpuset.cpus echo isolated > A/B/cpuset.cpus.partition cat cpuset.cpus.isolated 2-3 echo 0 > /sys/devices/system/cpu/cpu1/online cat A/B/cpuset.cpus.partition isolated invalid cat cpuset.cpus.isolated 2-3 When A is invalidated, partition_xcpus_del() gives CPUs 0,2-31 back to top cpuset. Both A and top cpuset are root partitions, so isolated_cpus is left untouched although CPUs 2-3 were distributed to the isolated B. B is then invalidated with an invalid parent, and nothing releases CPUs 2-3 either. Make partition_xcpus_del() always set the isolation state of the given back CPUs to the state of the parent that receives them. As the effective_xcpus of a partition covers the CPUs distributed to its descendants, the isolation state of those CPUs is settled at the same time. Boot-time isolated CPUs are still preserved by isolated_cpu_update(). compute_partition_effective_cpumask() invalidates a child partition without going through partition_xcpus_del(), so do the same there: the CPUs of the invalidated child take the isolation state of its parent. As the parent may be shrunk and its effective_xcpus not updated yet, only do so for the CPUs the parent still owns. This is to keep the isolation state correct for now, the in-place invalidation here will be removed later in the partition rework. isolated_cpus_update() assumes the old and new states are different, which no longer holds now that partition_xcpus_del() proceeds regardless of the states. Drop its @old_prs argument and the WARN_ON_ONCE() so that it simply sets the isolation state of the given CPUs, and use it everywhere. The state check in partition_xcpus_add() is dropped as well, as setting the state is a no-op when the states are the same. isolated_cpus_release() is no longer needed and is removed. Fixes: 11e5f407b64a ("cgroup/cpuset: Keep track of CPUs in isolated partitions") Reported-by: Guopeng Zhang Closes: https://lore.kernel.org/all/20261105130344.664336-4-guopeng.zhang@linux.dev/ Signed-off-by: Ridong Chen --- kernel/cgroup/cpuset.c | 98 ++++++++---------------------------------- 1 file changed, 19 insertions(+), 79 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 06ceeb0ac8c0..c7d4cfb615b7 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1244,17 +1244,17 @@ static bool isolated_cpu_update(int new_prs, int cpu) } /* - * isolated_cpus_update - Update the isolated_cpus mask - * @old_prs: old partition_root_state - * @new_prs: new partition_root_state - * @xcpus: exclusive CPUs with state change + * isolated_cpus_update - Set the isolation state of @xcpus + * @new_prs: partition root state that @xcpus will belong to + * @xcpus: exclusive CPUs whose isolation state may change + * + * CPUs isolated at boot time are kept isolated. */ -static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus) +static void isolated_cpus_update(int new_prs, struct cpumask *xcpus) { bool updated = false; int cpu; - WARN_ON_ONCE(old_prs == new_prs); lockdep_assert_held(&callback_lock); lockdep_assert_held(&cpuset_mutex); for_each_cpu(cpu, xcpus) @@ -1263,45 +1263,6 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus update_housekeeping = true; } -/* - * isolated_cpus_release - Remove the relevant CPUs in @xcpus from isolated_cpus - * @cs: the current cpuset - * @xcpus: the set of effective xcpus to be considered for removal - * - * This function is called when an isolated partition is invalidated or when - * some of its effective xcpus are to be removed from isolated_cpus due to - * changes in parent cpuset. The given @xcpus must be modifiable as the function - * will update its value to determine the right set of CPUs to be removed. - */ -static void isolated_cpus_release(struct cpuset *cs, struct cpumask *xcpus) -{ - struct cpuset *ancestor = parent_cs(cs); - struct cpuset *iancestor = NULL; - - /* - * Search the furthest isolated partition root ancestor available - * until top_cpuset or a remote partition root is hit. - */ - for (; ancestor; ancestor = parent_cs(ancestor)) { - if (ancestor->partition_root_state == PRS_ISOLATED) - iancestor = ancestor; - if (is_remote_partition(ancestor)) - break; - } - - /* - * If a furthest isolated partition acnestor is found, use it to - * determine which of the CPUs in @xcpus should be removed from - * isolated_cpus. Otherwise, all of them will be removed. - */ - if (iancestor && !cpumask_andnot(xcpus, xcpus, iancestor->effective_xcpus)) - return; /* No CPU should be removed from isolated_cpus */ - - spin_lock_irq(&callback_lock); - isolated_cpus_update(PRS_ISOLATED, PRS_ROOT, xcpus); - spin_unlock_irq(&callback_lock); -} - /* * partition_xcpus_add - Add new exclusive CPUs to partition * @new_prs: new partition_root_state @@ -1325,9 +1286,7 @@ static void partition_xcpus_add(int new_prs, struct cpuset *parent, if (parent == &top_cpuset) cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus); - if (new_prs != parent->partition_root_state) - isolated_cpus_update(parent->partition_root_state, new_prs, - xcpus); + isolated_cpus_update(new_prs, xcpus); cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus); } @@ -1355,9 +1314,8 @@ static void partition_xcpus_del(int old_prs, struct cpuset *parent, if (parent == &top_cpuset) cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus); - if (old_prs != parent->partition_root_state) - isolated_cpus_update(old_prs, parent->partition_root_state, - xcpus); + /* CPUs given back, including those of descendants, take parent's state */ + isolated_cpus_update(parent->partition_root_state, xcpus); cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus); cpumask_and(parent->effective_cpus, parent->effective_cpus, cpu_active_mask); @@ -1612,6 +1570,7 @@ static void compute_partition_effective_cpumask(struct cpuset *cs, struct cgroup_subsys_state *css; struct cpuset *child; bool populated = partition_is_populated(cs, NULL); + static cpumask_t xcpus; /* Protected by cpuset_mutex */ /* * Check child partition roots to see if they should be invalidated @@ -1640,14 +1599,15 @@ static void compute_partition_effective_cpumask(struct cpuset *cs, int parent_prs = cs->partition_root_state; /* - * Invalidate child partition and update isolated_cpus - * if necessary. + * Invalidate child partition. Its CPUs still owned by + * cs take the isolation state of cs. effective_xcpus + * of cs may not be updated yet, so recompute it. */ spin_lock_irq(&callback_lock); WRITE_ONCE(child->prs_err, PERR_NOCPUS); - if ((old_prs == PRS_ISOLATED) && (parent_prs == PRS_ROOT)) - isolated_cpus_update(PRS_ISOLATED, PRS_ROOT, - child->effective_xcpus); + compute_excpus(cs, &xcpus); + cpumask_and(&xcpus, &xcpus, child->effective_xcpus); + isolated_cpus_update(parent_prs, &xcpus); child->partition_root_state = -old_prs; spin_unlock_irq(&callback_lock); notify_partition_change(child, old_prs); @@ -2090,22 +2050,8 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, * * A partition error happens when parent has tasks and all * its effective CPUs will have to be distributed out. - * - * For an isolated partition with a shrunk root partition parent - * we may need to return some or all of its isolated CPUs. */ nocpu |= cpumask_empty(tmp->delmask); - if ((parent_prs == PRS_ROOT) && (old_prs == PRS_ISOLATED)) { - cpumask_clear(tmp->addmask); - if (nocpu) - cpumask_copy(tmp->addmask, cs->effective_xcpus); - else if (!cpumask_subset(cs->effective_xcpus, parent->effective_xcpus)) - cpumask_andnot(tmp->addmask, cs->effective_xcpus, - parent->effective_xcpus); - if (!cpumask_empty(tmp->addmask)) - isolated_cpus_release(cs, tmp->addmask); - /* Expansion of parent's effective_xcpus is handled below */ - } if (nocpu) { part_error = PERR_NOCPUS; if (is_partition_valid(cs)) @@ -2345,18 +2291,12 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, /* * When parent is not a valid partition root, * child partition roots become invalid too. - * - * For a to be invalidated isolated partition, - * call return_isolated_cpus() to remove the - * relevant CPUs from isolated_cpus. + * The isolation state of their CPUs has been + * settled when the parent gave them back. */ if (is_partition_valid(cp)) new_prs = -old_prs; - if (old_prs == PRS_ISOLATED) { - cpumask_copy(tmp->delmask, cp->effective_xcpus); - isolated_cpus_release(cp, tmp->delmask); - } WRITE_ONCE(cp->prs_err, is_partition_invalid(parent) ? PERR_INVPARENT : PERR_NOTPART); @@ -3132,7 +3072,7 @@ static int update_prstate(struct cpuset *cs, int new_prs) if (!is_partition_valid(cs)) reset_partition_data(cs); else if (isolcpus_updated) - isolated_cpus_update(old_prs, new_prs, tmpmask.new_cpus); + isolated_cpus_update(new_prs, tmpmask.new_cpus); spin_unlock_irq(&callback_lock); /* Force update if partition is disabled & update effective_xcpus */ -- 2.34.1