From 0a68853de27b522bca2b9934127277185374a24f Mon Sep 17 00:00:00 2001 From: Sun Shaojie Date: Wed, 27 May 2026 14:43:28 +0800 Subject: [PATCH 1/3] cgroup/cpuset: Use effective_xcpus in partcmd_update add/del mask calculation When sibling CPU exclusion occurs, a partition's user_xcpus may contain CPUs that were never actually granted to it. These CPUs are present in user_xcpus(cs) but not in cs->effective_xcpus. The partcmd_update path in update_parent_effective_cpumask() uses user_xcpus(cs) (via the local variable xcpus) to compute the addmask (CPUs to return to parent) and delmask (CPUs to request from parent). This is incorrect: 1) When newmask removes a CPU that was previously excluded by a sibling, addmask incorrectly includes that CPU and tries to return it to the parent even though the partition never actually owned it, causing CPU overlap with sibling partitions and triggering warnings in generate_sched_domains(). 2) When newmask adds a previously excluded CPU that is now available, delmask fails to request it from the parent because user_xcpus(cs) already includes it. Fix this by using cs->effective_xcpus instead of user_xcpus(cs) in all partcmd_update paths that calculate addmask or delmask, including the PERR_NOCPUS error handling paths. Reproducers: Example 1 - Removing a sibling-excluded CPU incorrectly returns it: # cd /sys/fs/cgroup # echo "0-1" > a1/cpuset.cpus # echo "root" > a1/cpuset.cpus.partition # echo "0-2" > b1/cpuset.cpus # echo "root" > b1/cpuset.cpus.partition # echo "2" > b1/cpuset.cpus # cat cpuset.cpus.effective # Actual: 0-1,3 Expected: 3 Example 2 - Expanding to a previously excluded CPU fails to request it: # cd /sys/fs/cgroup # echo "0-1" > a1/cpuset.cpus # echo "root" > a1/cpuset.cpus.partition # echo "0-2" > b1/cpuset.cpus # echo "root" > b1/cpuset.cpus.partition # echo "member" > a1/cpuset.cpus.partition # echo "1-2" > b1/cpuset.cpus # cat cpuset.cpus.effective # Actual: 0-1,3 Expected: 0,3 Fixes: 2a3602030d80 ("cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict") Cc: stable@vger.kernel.org # v7.0+ Suggested-by: Zhang Guopeng Signed-off-by: Sun Shaojie Reviewed-by: Waiman Long Signed-off-by: Tejun Heo --- kernel/cgroup/cpuset.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 5c33ab20cc20..c9e14fda3d6f 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1811,9 +1811,9 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, * Compute add/delete mask to/from effective_cpus * * For valid partition: - * addmask = exclusive_cpus & ~newmask + * addmask = effective_xcpus & ~newmask * & parent->effective_xcpus - * delmask = newmask & ~exclusive_cpus + * delmask = newmask & ~effective_xcpus * & parent->effective_xcpus * * For invalid partition: @@ -1825,11 +1825,11 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, deleting = cpumask_and(tmp->delmask, newmask, parent->effective_xcpus); } else { - cpumask_andnot(tmp->addmask, xcpus, newmask); + cpumask_andnot(tmp->addmask, cs->effective_xcpus, newmask); adding = cpumask_and(tmp->addmask, tmp->addmask, parent->effective_xcpus); - cpumask_andnot(tmp->delmask, newmask, xcpus); + cpumask_andnot(tmp->delmask, newmask, cs->effective_xcpus); deleting = cpumask_and(tmp->delmask, tmp->delmask, parent->effective_xcpus); } @@ -1868,7 +1868,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, part_error = PERR_NOCPUS; deleting = false; adding = cpumask_and(tmp->addmask, - xcpus, parent->effective_xcpus); + cs->effective_xcpus, parent->effective_xcpus); } } else { /* @@ -1890,7 +1890,8 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, part_error = PERR_NOCPUS; if (is_partition_valid(cs)) adding = cpumask_and(tmp->addmask, - xcpus, parent->effective_xcpus); + cs->effective_xcpus, + parent->effective_xcpus); } else if (is_partition_invalid(cs) && !cpumask_empty(xcpus) && cpumask_subset(xcpus, parent->effective_xcpus)) { struct cgroup_subsys_state *css; From 645c3b7ef1a7eed9627664bd11d7a8eb4519ee15 Mon Sep 17 00:00:00 2001 From: Sun Shaojie Date: Wed, 27 May 2026 15:05:09 +0800 Subject: [PATCH 2/3] cgroup/cpuset: Add test cases for sibling CPU exclusion on partition update When sibling CPU exclusion occurs, a partition's effective_xcpus may be a subset of its user_xcpus. The partcmd_update path must use effective_xcpus instead of user_xcpus when calculating CPUs to return to or request from the parent. Add two test cases to verify this behavior: 1) Narrowing cpuset.cpus to only the sibling-excluded CPUs should not return CPUs to parent that the partition never actually owned. 2) Expanding cpuset.cpus after a sibling becomes a member should correctly request the additional CPUs from parent. Co-developed-by: Zhang Guopeng Signed-off-by: Zhang Guopeng Signed-off-by: Sun Shaojie Reviewed-by: Waiman Long Signed-off-by: Tejun Heo --- tools/testing/selftests/cgroup/test_cpuset_prs.sh | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index a56f4153c64d..683b05062810 100755 --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh @@ -492,6 +492,16 @@ REMOTE_TEST_MATRIX=( " C1-5:P1 . C1-4:P1 C2-3 . . \ . . . P1 . . p1:5|c11:1-4|c12:5 \ p1:P1|c11:P1|c12:P-1" + # Narrowing cpuset.cpus to previously sibling-excluded CPUs should + # not return CPUs that were never actually owned. + " C1-4:P1 . C1-2:P1 C1-3:P2 . . \ + . . . C3 . . p1:4|c11:1-2|c12:3 \ + p1:P1|c11:P1|c12:P2 3" + # Expanding cpuset.cpus to include a previously sibling-excluded CPU + # after the sibling has become a member should correctly request it. + " C1-4:P1 . C1-2:P1 C1-3:P2 . . \ + . . P0 C2-3 . . p1:1,4|c11:1|c12:2-3 \ + p1:P1|c11:P0|c12:P2 2-3" ) # From 57aff991119693e09b414aff3267c0eae5e81da0 Mon Sep 17 00:00:00 2001 From: Ridong Chen Date: Tue, 2 Jun 2026 17:10:38 +0800 Subject: [PATCH 3/3] cgroup/cpuset: Change Ridong's email The chenridong@huaweicloud.com is no longer a valid email, replace it with the personal email ridong.chen@linux.dev Signed-off-by: Ridong Chen Acked-by: Waiman Long Signed-off-by: Tejun Heo --- MAINTAINERS | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/MAINTAINERS b/MAINTAINERS index 74c86cf9bc65..634eb67acd06 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6526,7 +6526,7 @@ F: include/linux/blk-cgroup.h CONTROL GROUP - CPUSET M: Waiman Long -R: Chen Ridong +R: Ridong Chen L: cgroups@vger.kernel.org S: Maintained T: git git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git