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Fri, 30 Oct 2026 19:07:14 +0000 (UTC) Received: from llong-thinkpadp16vgen1.rmtusnh.csb (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id EB16F1956087; Fri, 30 Oct 2026 19:07:12 +0000 (UTC) From: Waiman Long To: Ridong Chen , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Shuah Khan Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Guopeng Zhang , Waiman Long Subject: [PATCH v2 1/3] cgroup/cpuset: Fix incorrect CPU accounting with parent's effective_xcpus expansion Date: Fri, 30 Oct 2026 15:06:59 -0400 Message-ID: <20261030190701.78308-2-longman@redhat.com> In-Reply-To: <20261030190701.78308-1-longman@redhat.com> References: <20261030190701.78308-1-longman@redhat.com> X-Mailing-List: linux-kselftest@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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Commit ec0254b9eb49 ("cgroup/cpuset: Release invalid isolated CPUs with a shrunk root partition parent") fixes incorrect isolated_cpus accounting when contraction of a parent's effective_xcpus can cause a child partition to lose isolated CPUs. Expansion of parent's effective_cpus can also allow a child partition to gain more effective_xcpus. However, the current code doesn't handle this case correctly leading to incorrect effective_cpus and isolated_cpus accounting. Fix that by looking for this possible expansion of effective_xcpus and perform the proper accounting action. New test cases are added to test this effective_xcpus expansion scenarios. Reported-by: Guopeng Zhang Link: https://lore.kernel.org/lkml/20261027123837.100909-1-guopeng.zhang@linux.dev Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 12 ++++++++++++ tools/testing/selftests/cgroup/test_cpuset_prs.sh | 15 +++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 3219f927c35e..39c81a0a8ab9 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2097,6 +2097,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, 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; @@ -2106,11 +2107,22 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, parent->effective_xcpus); } else if ((parent_prs == PRS_ISOLATED) && ((old_prs == PRS_ROOT) || (old_prs == -PRS_ROOT))) { + /* Parent partition state changed to PRS_ISOLATED */ part_error = PERR_ISOPARENT; if (old_prs == PRS_ROOT) { cpumask_copy(tmp->addmask, cs->effective_xcpus); adding = true; } + } else if (is_partition_valid(cs) && + !cpumask_equal(tmp->delmask, cs->effective_xcpus)) { + /* + * If there is an expansion of parent's effective_xcpus, + * we may take more xcpus from parent. The parent's + * effective_cpus should still have active CPUs or nocpu + * should have been set. + */ + deleting = cpumask_andnot(tmp->delmask, tmp->delmask, + cs->effective_xcpus); } else if (is_partition_invalid(cs)) { struct cgroup_subsys_state *css; struct cpuset *child; diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index 83ef6c781af3..844efdf029cd 100755 --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh @@ -531,6 +531,21 @@ TEST_MATRIX=( " C1-4:P1 C3-4:P2 . . T:C4-6 . . . 0 A1:5-6|A2:4 A1:P1|A2:P2 4" " C1-4:P1 C1-2:P2 . . T:C4-6 . . . 0 A1:4-6|A2:4-6 A1:P1|A2:P-2 ." + # The extra CPUs gained by a child partition when its parent expands the + # exclusive CPUs have to be taken away from the parent. + " C2-6:X2-5:P1 CX3-6:P1 \ + . . X2-6 . . . 0 A1:2|A2:3-6|XA2:3-6 A1:P1|A2:P1 ." + " C2-6:X2-5:P1 CX3-6:P2 \ + . . X2-6 . . . 0 A1:2|A2:3-6|XA2:3-6 A1:P1|A2:P2 3-6" + + # Both expansion and contraction of parent's effective_xcpus will be + # correctly handled in child partition and the child can be invalidated + # if a populated parent could lose all its effective_cpus. + " C2-6:X2-5:P1 CX3,5-6:P2 \ + . . X4-6 . . . 0 A1:4|A2:5-6|XA2:5-6 A1:P1|A2:P2 5-6" + " C2-6:X2-5:P1 CX3-6:P2 \ + . . T:X4-6 . . . 0 A1:4-6|A2:4-6 A1:P1|A2:P-2 ." + # # old-A1 old-A2 old-A3 old-B1 new-A1 new-A2 new-A3 new-B1 fail ECPUs Pstate ISOLCPUS # ------ ------ ------ ------ ------ ------ ------ ------ ---- ----- ------ -------- -- 2.56.0