Re: [RFC][PATCH] sched/wait_bit: Introduce wait_var_event()/wake_up_var()

[Peter Zijlstra]

On Thu, Mar 15, 2018 at 02:45:20PM +0000, David Howells wrote:
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > Does the below address things sufficiently clear?
> 
> Yep.

Thanks!

> > +wait_queue_head_t *__var_waitqueue(void *p)
> > +{
> > +	if (BITS_PER_LONG == 64) {
> > +		unsigned long q = (unsigned long)p;
> > +
> > +		return bit_waitqueue((void *)(q & ~1), q & 1);
> > +	}
> > +	return bit_waitqueue(p, 0);
> > +}
> 
> You might be better off not using bit_waitqueue() but rather do the
> calculation directly since you don't actually have a bit number.

Yes, I did that in patch 11. The initial version uses the exact same
stuff wait_on_atomic_t() uses to avoid spurious changes.