On 8/23/26 10:01 PM, Guopeng Zhang wrote:
From: Guopeng Zhang <[email protected]>isolated_cpus tracks CPUs isolated with isolcpus= as well as CPUs in isolated cpuset partitions. When an isolated partition is released, isolated_cpus_update() removes its whole CPU mask. This also clears CPUs which were already isolated at boot. This can be reproduced on a cgroup v2 system booted with isolcpus=domain,15: cd /sys/fs/cgroup echo +cpuset > cgroup.subtree_control mkdir cpuset-repro echo 15 > cpuset-repro/cpuset.cpus echo isolated > cpuset-repro/cpuset.cpus.partition echo member > cpuset-repro/cpuset.cpus.partition cat cpuset.cpus.isolated CPU 15 is absent before the change. It must remain in cpuset.cpus.isolated after the partition is released. Update isolated_cpus one CPU at a time and keep CPUs outside the boot-time domain housekeeping mask isolated. Fixes: c188f33c864e ("cgroup/cpuset: Account for boot time isolated CPUs") Signed-off-by: Guopeng Zhang <[email protected]> --- kernel/cgroup/cpuset.c | 39 +++++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 10 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index d100634fa12b..2538faac9aba 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1259,6 +1259,28 @@ static void reset_partition_data(struct cpuset *cs) cpumask_copy(cs->effective_cpus, parent->effective_cpus); }+/* Return true if isolated_cpus changes. */+static bool isolated_cpu_update(int new_prs, int cpu) +{ + lockdep_assert_held(&callback_lock); + lockdep_assert_held(&cpuset_mutex); + + if (new_prs == PRS_ISOLATED) { + if (cpumask_test_cpu(cpu, isolated_cpus)) + return false; + cpumask_set_cpu(cpu, isolated_cpus); + return true; + } + + /* CPUs isolated at boot must remain isolated. */ + if (!cpumask_test_cpu(cpu, + housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT)) || + !cpumask_test_cpu(cpu, isolated_cpus)) + return false; + cpumask_clear_cpu(cpu, isolated_cpus); + return true; +} + /* * isolated_cpus_update - Update the isolated_cpus mask * @old_prs: old partition_root_state @@ -1267,19 +1289,16 @@ static void reset_partition_data(struct cpuset *cs) */ static void isolated_cpus_update(int old_prs, 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); - if (new_prs == PRS_ISOLATED) { - if (cpumask_subset(xcpus, isolated_cpus)) - return; - cpumask_or(isolated_cpus, isolated_cpus, xcpus); - } else { - if (!cpumask_intersects(xcpus, isolated_cpus)) - return; - cpumask_andnot(isolated_cpus, isolated_cpus, xcpus); - } - update_housekeeping = true; + for_each_cpu(cpu, xcpus) + updated |= isolated_cpu_update(new_prs, cpu); + if (updated) + update_housekeeping = true; }/*
The code is technically correct. However, handling it one CPU at a time is less efficient from my point of view. It can be handled more efficiently from the cpumask level. I do notice that the new isolated_cpu_update() helper is being used in a later patch in your larger series. Maybe that is the reason why you do it this way.
I am OK with this change. Acked-by: Waiman Long <[email protected]>
