On 7/5/23 01:56, Miaohe Lin wrote:
On 2023/7/5 11:14, Waiman Long wrote:
On 7/4/23 07:30, Miaohe Lin wrote:
kthread_is_per_cpu() can be called directly without checking whether
PF_KTHREAD is set in task->flags. So remove PF_KTHREAD check to make
code more concise.
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 58e6f18f01c1..601c40da8e03 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1230,7 +1230,7 @@ static void update_tasks_cpumask(struct cpuset *cs, struct cpumask *new_cpus)
/*
* Percpu kthreads in top_cpuset are ignored
*/
- if ((task->flags & PF_KTHREAD) && kthread_is_per_cpu(task))
+ if (kthread_is_per_cpu(task))
continue;
cpumask_andnot(new_cpus, possible_mask, cs->subparts_cpus);
} else {
The initial intention was to ignore only percpu kthreads. The current code likely ignore all the kthreads. Removing the PF_KTHREAD flag, however, may introduce unexpected regression at this point. I would like to hold off for now until more investigation are done.
IMHO, the current code will ignore only percpu kthreads:
1.If PF_KTHREAD is set in task->flags, this patch doesn't make any difference.
2.If PF_KTHREAD is not set in task->flags, kthread_is_per_cpu will *always return false*. So this patch doesn't make any functional change.
bool kthread_is_per_cpu(struct task_struct *p)
{
struct kthread *kthread = __to_kthread(p);
if (!kthread)
return false;
....
}
static inline struct kthread *__to_kthread(struct task_struct *p)
{
void *kthread = p->worker_private;
if (kthread && !(p->flags & PF_KTHREAD))
^^^^^^^^^^^^^^^^^^^^^^
PF_KTHREAD is not set, so kthread = NULL.
kthread = NULL;
return kthread;
}
Or am I miss something? Thanks for comment and review.
Yes, you are right. I was that conscious when I reviewed the patch last
night :-)
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
