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 | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 3d2d28f0fd03..850334dbc36a 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2050,6 +2050,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, struct cpuset *parent = parent_cs(cp); bool remote = is_remote_partition(cp); bool update_parent = false; + bool empty_xcpus;
old_prs = new_prs = cp->partition_root_state;
@@ -2160,20 +2161,14 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, new_prs = cp->partition_root_state; }
+ empty_xcpus = cpumask_empty(cp->exclusive_cpus); 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)) + if (((new_prs > 0) && empty_xcpus) || + ((cp != cs) && !empty_xcpus)) compute_excpus(cp, cp->effective_xcpus); - - /* - * Make sure effective_xcpus is properly set for 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) reset_partition_data(cp); spin_unlock_irq(&callback_lock);