Since commit f62a5d39368e ("cgroup/cpuset: Remove remote_partition_check() & make update_cpumasks_hier() handle remote partition"), the compute_effective_exclusive_cpumask() helper was extended to strip exclusive CPUs from siblings when computing effective_xcpus (cpuset.cpus.exclusive.effective). This helper was later renamed to compute_excpus() in commit 86bbbd1f33ab ("cpuset: Refactor exclusive CPU mask computation logic").
This helper is supposed to be used consistently to compute effective_xcpus. However, there is an exception within the callback critical section in update_cpumasks_hier() when exclusive_cpus of a valid partition root is empty. This can cause effective_xcpus value to differ depending on where exactly it is last computed. Fix this by using compute_excpus() in this case to give a consistent result.
Signed-off-by: Waiman Long longman@redhat.com --- kernel/cgroup/cpuset.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index da2b3b51630e..894131f47f78 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2168,17 +2168,13 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, spin_lock_irq(&callback_lock); cpumask_copy(cp->effective_cpus, tmp->new_cpus); cp->partition_root_state = new_prs; - if (!cpumask_empty(cp->exclusive_cpus) && (cp != cs)) - compute_excpus(cp, cp->effective_xcpus); - /* - * Make sure effective_xcpus is properly set for a valid - * partition root. + * Need to compute effective_xcpus if either exclusive_cpus + * is non-empty or it is a valid partition root. */ - if ((new_prs > 0) && cpumask_empty(cp->exclusive_cpus)) - cpumask_and(cp->effective_xcpus, - cp->cpus_allowed, parent->effective_xcpus); - else if (new_prs < 0) + if ((new_prs > 0) || !cpumask_empty(cp->exclusive_cpus)) + compute_excpus(cp, cp->effective_xcpus); + if (new_prs <= 0) reset_partition_data(cp); spin_unlock_irq(&callback_lock);