cgroup/cpuset: Drop redundant no-cpu check in partcmd_update with newmask

update_parent_effective_cpumask() with a non-NULL newmask is only ever
reached from partition_cpus_change(), and only after validate_partition()
has checked the very same condition with the very same arguments:

  tasks_nocpu_error(parent_cs(cs), cs, trialcs->effective_xcpus)

since newmask is exactly trialcs->effective_xcpus and both functions use
parent_cs(cs) as the parent. cs, parent and cpu_active_mask cannot change
in between either, as cpuset_mutex and cpu_read_lock are held for the
whole operation. Hence

  nocpu = tasks_nocpu_error(parent, cs, newmask);

is always false here and the block that turns a "nocpu" condition into
PERR_NOCPUS is dead code. A new CPU list that would drain the parent is
fully handled by validate_partition(), which routes the write to
partcmd_invalidate and hands the partition's CPUs back to the parent.

The "!adding || !cpumask_intersects(addmask, cpu_active_mask)" test that
guards the block does not change this: the block can only be entered when
nocpu is true, and that never happens here.

Drop the redundant check and the dead PERR_NOCPUS block, and leave a
comment pointing at where the "parent could be drained" case is handled.
The empty-newmask check in the same branch is left alone: it validates
the newmask argument of this function, while what is removed here is a
decision that belongs to validate_partition().

No functional change.

Signed-off-by: Shaojie Sun <sunshaojie@kylinos.cn>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions