From 345f40166694e60db6d5cf02233814bb27ac5dec Mon Sep 17 00:00:00 2001 From: sunshaojie Date: Wed, 13 May 2026 18:37:38 +0800 Subject: [PATCH] cgroup/cpuset: Return only actually allocated CPUs during partition invalidation In update_parent_effective_cpumask() with partcmd_invalidate, the CPUs to return to the parent are computed as: adding = cpumask_and(tmp->addmask, xcpus, parent->effective_xcpus); where xcpus = user_xcpus(cs) which returns cs->exclusive_cpus (if set) or cs->cpus_allowed. When exclusive_cpus is not set, user_xcpus(cs) can contain CPUs that were never actually granted to the partition due to sibling exclusion in compute_excpus(). Consequently, the invalidation may return CPUs to the parent that remain in use by sibling partitions, causing overlapping effective_cpus and triggering the WARN_ON_ONCE(1) in generate_sched_domains(). Use cs->effective_xcpus instead, which reflects the CPUs actually granted to this partition. Reproducer (on a 4-CPU machine): cd /sys/fs/cgroup mkdir a1 b1 # a1 becomes partition root with CPUs 0-1 echo "0-1" > a1/cpuset.cpus echo "root" > a1/cpuset.cpus.partition # b1 becomes partition root with CPUs 1-2, but sibling exclusion # reduces its effective_xcpus to CPU 2 only echo "1-2" > b1/cpuset.cpus echo "root" > b1/cpuset.cpus.partition # b1 changes cpus_allowed to 0-1 -> partition invalidation echo "0-1" > b1/cpuset.cpus # Expected: CPUs 2-3 (only CPU 2 returned from b1) # Actual: CPUs 1-3 (CPU 0-1 returned, overlapping with a1) cat cpuset.cpus.effective dmesg will also show a WARNING from generate_sched_domains() reporting overlapping partition root effective_cpus. Fixes: 2a3602030d80 ("cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict") Cc: stable@vger.kernel.org # v7.0+ Signed-off-by: sunshaojie Tested-by: Chen Ridong Reviewed-by: Chen Ridong Reviewed-by: Waiman Long Signed-off-by: Tejun Heo --- kernel/cgroup/cpuset.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index e84e801e22cf..5c33ab20cc20 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1718,7 +1718,8 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, */ if (is_partition_valid(parent)) adding = cpumask_and(tmp->addmask, - xcpus, parent->effective_xcpus); + cs->effective_xcpus, + parent->effective_xcpus); if (old_prs > 0) new_prs = -old_prs;