# Re: \[RFC PATCH 06/18\] signal/kthread: Initial implementation of kthread signal handling

- From: Petr Mladek \<hidden\>
- Date: 2015-06-16 07:54:26 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2015/06/4516480
- Thread: https://ratatoskr.run/linux-nfs/2015/06/4510097/t.md

```text
On Mon 2015-06-15 21:14:29, Oleg Nesterov wrote:
> Ah, understand. You think that we need to take ->siglock in advance
> to avoid the race with SIGCONT?

exactly

> No, we don't. Let me show you the code I suggested again:
> 
> 	void kthread_do_signal_stop(void)
> 	{
> 		spin_lock_irq(&curtent->sighand->siglock);
> 		if (current->jobctl & JOBCTL_STOP_DEQUEUED)
> 			__set_current_state(TASK_STOPPED);
> 		spin_unlock_irq(&current->sighand->siglock);
> 
> 		schedule();
> 	}
> 	
> so you can dequeue_signal() and call kthread_do_signal_stop() without
> holding ->siglock. We can rely on JOBCTL_STOP_DEQUEUED bit. SIGCONT
> clears it, so kthread_do_signal_stop() can't race.

Heureka, I have got it. I have previously missed the meaning of the
JOBCTL_STOP_DEQUEUED bit. Thanks for explanation.

Best Regards,
Petr
```