From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.190 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794052906; b=d4L7u0GYL4791zqbFjxjOVmh5hZeIKHRv8PQ/ZU6EDZOS99vkvherFF4263JJmoW1ZYJ 7qqnH7fJiOsrsenOD/OB7XzEfIdwC2if5RLOGO2AUp4iiiUM2wdi9zLKTTYKaSAzB0p6d nBPijlU/vBFbJ1K9sSUeqdhIC4EU9X86mxMaYFviJICtB/JTI9RlVA3M+mydENkhLSAy0 uyKYoYqtmJP6urjw5xapCCNGq7xeqfoJcnAj6UUPO7I5ATODgZWcn+s9DdfFaNQll1jxt CJAUsuUVlPWBxYEayl3OntMhbfQc7/pSxtBH63y4G7eu8Q5j1MbAinRZ1L14B2C2Mig== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794052906; 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=0xbtiSBDr+hThAidCr/J/LOLvKxahveldkgX7OwOhiM=; b=G+wf/DI889gZT7sAYxsUjp2+4FzShh7bfCuxyRSm5mbaYUbmpWY36AxqO0E+mCnpLm2M rN+ITwFSeMK2+HTb29zNKRv+bcwYC4EoF3wrO4zKFidfpovSMhba9e7oH2tK8klIr9Ffu XNkiE8Wyj3gEGTs8+RBBJGbu9WqgD9g1gLV8x2BVjBTIHfgE1ZYklkgYfEbUkdOcrs/Fc AvWcbRlZsJl2oOVhOK24dlAAaA+LkQ4DT03/h7SI2yFytmdfdb5Zb4qhAYCX1ZjMSiZGT 9M8astH7zlHXk2wU79MbuRoEYghrc5RsBkNjjkz2kKguBcy7eSR/lrqRk/MW4BoJBZA== 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="U1mI2/Zf"; arc=none smtp.remote-ip=95.215.58.190 Received: from mta1.migadu.com (out-190.mta1.migadu.com [95.215.58.190]) (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 63D04606A32E for ; Sat, 7 Nov 2026 12:01:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 63D04606A32E 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=U1mI2/Zf X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Z5pn2ufKLm0b280oCpw4ducPgTBGcdOMUC/u1nj/vY8=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794052903; v=1; x=1794657703; b=U1mI2/ZfhBe9kwpur/B4hr3mZx5o23Mt+fTSFP1t/MLnTO2kYCghhYbhYTqzgXy9t6gRMKVo uZqMmYwI/kEI18Wz5Z7CkTl/nEPlexPnBEaolhJznzmcgOoUENgZtBBO+0/e9aj2R9jXCSWdr8V SMO5QhniiX5MMVJCJJHHGOZQ= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 4f9bfeffe3ff14be; Sat, 07 Nov 2026 12:01:43 +0000 X-Mizu-Trace-ID: 4f9bfeffe3ff14be 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 v3 3/4] cpuset: settle isolation state when CPUs are given back to parent Date: Sat, 7 Nov 2026 20:00:59 +0800 Message-Id: <20261107120100.3587595-4-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261107120100.3587595-1-ridong.chen@linux.dev> References: <20261107120100.3587595-1-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_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. 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 85e5b529d144..fc9de6e16ff5 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); @@ -2080,22 +2040,8 @@ 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 +2287,12 @@ 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); @@ -3108,7 +3048,7 @@ 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, cs->effective_xcpus); + isolated_cpus_update(new_prs, cs->effective_xcpus); spin_unlock_irq(&callback_lock); /* Force update if partition is disabled & update effective_xcpus */ -- 2.34.1