From 0a68853de27b522bca2b9934127277185374a24f Mon Sep 17 00:00:00 2001 From: Sun Shaojie Date: Wed, 27 May 2026 14:43:28 +0800 Subject: 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(-) (limited to 'kernel') 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; -- cgit v1.2.3