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

- From: Steven Rostedt \<hidden\>
- Date: 2015-06-08 17:48:22 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2015/06/4511292
- Thread: https://ratatoskr.run/linux-nfs/2015/06/4510097/t.md

```text
On Fri, 5 Jun 2015 18:10:21 +0200
Peter Zijlstra [ref] wrote:

> On Fri, Jun 05, 2015 at 05:01:08PM +0200, Petr Mladek wrote:
> > Many kthreads go into an interruptible sleep when there is nothing
> > to do. They should check if anyone did not requested the kthread
> > to terminate, freeze, or park in the meantime. It is easy to do
> > it a wrong way.
> 
> INTERRUPTIBLE is the wrong state to idle in for kthreads, use
> TASK_IDLE.
> 
> ---
> 
> commit 80ed87c8a9ca0cad7ca66cf3bbdfb17559a66dcf
> Author: Peter Zijlstra [ref]
> Date:   Fri May 8 14:23:45 2015 +0200
> 
>     sched/wait: Introduce TASK_NOLOAD and TASK_IDLE
>     
>     Currently people use TASK_INTERRUPTIBLE to idle kthreads and wait for
>     'work' because TASK_UNINTERRUPTIBLE contributes to the loadavg. Having
>     all idle kthreads contribute to the loadavg is somewhat silly.

Not to mention, tasks in TASK_UNINTERRUPTIBLE state for too long will
trigger hung task detection.


>     
>     Now mostly this works OK, because kthreads have all their signals
>     masked. However there's a few sites where this is causing problems and
>     TASK_UNINTERRUPTIBLE should be used, except for that loadavg issue.
>     
>     This patch adds TASK_NOLOAD which, when combined with
>     TASK_UNINTERRUPTIBLE avoids the loadavg accounting.
>     
>     As most of imagined usage sites are loops where a thread wants to
>     idle, waiting for work, a helper TASK_IDLE is introduced.
>     
>     Signed-off-by: Peter Zijlstra (Intel) [ref]

Acked-by: Steven Rostedt <redacted>

-- Steve

>     Cc: Julian Anastasov [ref]
>     Cc: Linus Torvalds [ref]
>     Cc: NeilBrown [ref]
>     Cc: Oleg Nesterov [ref]
>     Cc: Peter Zijlstra [ref]
>     Cc: Thomas Gleixner [ref]
>     Signed-off-by: Ingo Molnar [ref]
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
```