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SubjectRe: [PATCH 1/1] kthread: fix possible infinite wait for parking when kthread exits meanwhile
Well. I was going to ignore this patch, I will leave this to Thomas
anyway...

But can't resist, because I have to admit I dislike this one too ;)

On 10/25, Roman Pen wrote:
>
> int kthread_park(struct task_struct *k)
> {
> - struct kthread *kthread = to_live_kthread_and_get(k);
> + struct kthread *kthread;
> int ret = -ENOSYS;
>
> - if (kthread) {
> - if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
> + /*
> + * Here we try to be careful and handle the case, when kthread
> + * is going to die and will never park.

But why?

IMO we should not complicate this code for the case when the kernel
thread crashes.

> + do {
> + kthread = to_live_kthread_and_get(k);
> + if (!kthread)
> + break;
> + if (!__kthread_isparked(kthread)) {
> set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
> if (k != current) {
> wake_up_process(k);
> wait_for_completion(&kthread->parked);
> }
> }
> + if (k == current || __kthread_isparked(kthread))
> + /* The way out */
> + ret = 0;

And why do we need to restart if __kthread_isparked() is false? In this
case we know that we were woken up by the exiting kthread which won't
park anyway.

Oleg.

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