From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.42 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793962588; b=NiodVh2F34c+otx0t2p+BDHI+raKb9EbzcXaK3eXoS9oADal/6ooh7Bad2aGZgbWlhg3 qt0PeDr542uz+GodtCXoZ5ThfEOxKZsdJSlJNq3N5vDj+ufTCuqRHPqVTvkMrGQs90450 OJKNCrx/ealCkX0Ib2PcPKIlJDx7LyIgbeF5gtz+TSgbRMy8wuzAnDd0ocxNZ1XDDpAw/ AweSMQPoNltmrHvKaRuTywDn55l69Dec51MnDazxB6y8Uz4y10emD5Xl8W5TcOa9S+/FS nzVKgn15TLXas0P0/RdQeHoOyzbhIxg7+wgbwcyS8OqVsgS711iRgOk+LMB5s6z7gZA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793962588; 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=bi3IKqIUyGEPrpZA3dOlAN5KHpvQga9uYOwi+9H0Yb4=; b=nZ4H7ct1b3zV1vPHdUeb+xaibqwFD0S4BFvXpzk4zLli37MHog1HSMIgQCm+yZUbvDk1 cCIbYYPUGDhQFz0SaqEOiLIe94YPmmNaGIpUmS5uGbgrIYG52XmAyTYEjsSRQ28Je1Wp4 2X593xLUsjyMzyMF6euFOQJbl5g02Uz00pMPqfZRHzBYlCnV9McDKCGgCdFhAH0szlAUS /Z/KUYfUth4f9RHsR6B0LgHdgOjCOXpQZNeRtRqpIcizbPlg8HZIv0C6v/3cKchxTu3mz rJdt7WClZdPUMjMtuR0lkggOPc8ylA6JyRJnPtJanF1Qid32LBF6g178T9OT2wizb6g== 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=BS0UWPba; arc=none smtp.remote-ip=91.218.175.42 Received: from mta0.migadu.com (out-42.mta0.migadu.com [91.218.175.42]) (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 B4084606A331 for ; Fri, 6 Nov 2026 10:56:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org B4084606A331 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=BS0UWPba X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=AWLLW7Uy/s4T7E9FPecPDz3V1rl29a7Rnr/Fax4shEI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793962585; v=1; x=1794567385; b=BS0UWPbasE6+2icfuViHjejryOglQfSmidPJ2viBDE2F4S+RUUsU2r1VIWd7nBm2sQxS7y4n dviQlkSiNi5op1YrxWATFxGtvsFoZmHYNDz/l4BKdet4teel7l/E/tw9VwzwmVAV9PRrab5COEr 9ducdQyIOzjYh3qLLcu4zqf0= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id ade68e5ef1a406f3; Fri, 06 Nov 2026 10:56:25 +0000 X-Mizu-Trace-ID: ade68e5ef1a406f3 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 , Chen Ridong , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Sashiko , Guopeng Zhang , Ridong Chen Subject: [PATCH v2 3/4] cpuset: settle isolation state when CPUs are given back to parent Date: Fri, 6 Nov 2026 18:55:37 +0800 Message-Id: <20261106105538.2915492-4-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261106105538.2915492-1-ridong.chen@linux.dev> References: <20261106105538.2915492-1-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. 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_release() is no longer needed and is removed. Acked-by: Guopeng Zhang Signed-off-by: Ridong Chen --- kernel/cgroup/cpuset.c | 86 +++++++++++------------------------------- 1 file changed, 23 insertions(+), 63 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 85e5b529d144..a5ab9396eb61 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1264,42 +1264,21 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus } /* - * 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. + * isolated_cpus_set_state - Set the isolation state of @xcpus + * @prs: partition root state that @xcpus will belong to + * @xcpus: exclusive CPUs whose isolation state may change */ -static void isolated_cpus_release(struct cpuset *cs, struct cpumask *xcpus) +static void isolated_cpus_set_state(int prs, 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 */ + bool updated = false; + int cpu; - spin_lock_irq(&callback_lock); - isolated_cpus_update(PRS_ISOLATED, PRS_ROOT, xcpus); - spin_unlock_irq(&callback_lock); + lockdep_assert_held(&callback_lock); + lockdep_assert_held(&cpuset_mutex); + for_each_cpu(cpu, xcpus) + updated |= isolated_cpu_update(prs, cpu); + if (updated) + update_housekeeping = true; } /* @@ -1355,9 +1334,8 @@ 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_set_state(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 +1590,7 @@ 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 +1619,15 @@ 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_set_state(parent_prs, &xcpus); child->partition_root_state = -old_prs; spin_unlock_irq(&callback_lock); notify_partition_change(child, old_prs); @@ -2080,22 +2060,8 @@ 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)) @@ -2341,18 +2307,12 @@ 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); -- 2.34.1