[RFC PATCH 09/18] kthread: Make it easier to correctly sleep in iterant kthreads

[Peter Zijlstra]

On Mon, 2015-06-08 at 12:01 +0200, Petr Mladek wrote:

> Just to be sure. Do you suggest to use TASK_IDLE everywhere in
> kthreads or only when the uninterruptible sleep is really needed?

Always, only use INTERRUPTIBLE when you're actually interruptible, that
is you want signals or such muck to terminate your wait.

> IMHO, we should not use TASK_IDLE in freezable kthreads because
> it would break freezing.

How so? The task is IDLE, its not doing anything.

>  Well, we could freezable_schedule() but only
> on locations where it is safe to get freezed. Anyway, we need to
> be careful here.

s/freezed/frozen/

Bah, you made me look at the freezer code, karma reduction for you.

And this is the arch typical freeze point if ever there was one, you're
checking kthread_stop, if we can terminate the kthread, we can certainly
get frozen.

> BTW: What is the preferred way of freezing, please? Is it better
> to end up in the fridge or is it fine to call freezer_do_not_count();
> or set PF_NOFREEZE when it is safe?

freezable_schedule() is fine in this case.