Re: sem_lock() vs qspinlocks

[Davidlohr Bueso]

On Fri, 20 May 2016, Peter Zijlstra wrote:

> On Thu, May 19, 2016 at 10:39:26PM -0700, Davidlohr Bueso wrote:
> >  In addition, this makes me wonder if queued_spin_is_locked() should then be:
> >
> > -	return atomic_read(&lock->val);
> > +	return atomic_read(&lock->val) & _Q_LOCKED_MASK;
> >
> > And avoid considering pending waiters as locked.
>
> Probably

Similarly, and I know you hate it, but afaict, then semantically
queued_spin_is_contended() ought to be:

-       return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
+       return atomic_read(&lock->val);

Thanks,
Davidlohr