Re: [PATCH -v2 1/5] sched: Fix ttwu() race

[Paul E. McKenney]

On Thu, Jul 23, 2020 at 10:11:28PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 23, 2020 at 08:41:03PM +0100, Chris Wilson wrote:
> 
> > I am very sorry for the wild goose chase.
> 
> *phew*... all good then. I was starting to go a little ga-ga trying to
> make sense of things.
> 
> Arguably we should probably do something like:
> 
> 
> @@ -4555,7 +4572,7 @@ asmlinkage __visible void __sched preempt_schedule_irq(void)
>  int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
>  			  void *key)
>  {
> -	return try_to_wake_up(curr->private, mode, wake_flags);
> +	return try_to_wake_up(curr->private, mode, wake_flags & WF_SYNC);
>  }
>  EXPORT_SYMBOL(default_wake_function);

If you do:

Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

This was about nine hours of each of the default rcutorture scenarios.

							Thanx, Paul

> Since I don't think anybody uses anything other than WF_SYNC, ever. And
> the rest of the WF_flags are used internally.
> 
> Thanks Chris!