Re: [PATCH v4] lib/dlock-list: Scale dlock_lists_empty()

[Peter Zijlstra]

On Thu, Nov 09, 2017 at 09:24:08AM -0800, Davidlohr Bueso wrote:
> On Wed, 08 Nov 2017, Boqun Feng wrote:
> > Or worse:
> > 
> > 	 * CPU0				    CPU1
> > 	 * dlock_list_add()                 dlock_lists_empty()
> > 	 *					  smp_mb__before_atomic();
> > 	 *				      [L] atomic_read(used_lists)

Note that this is broken; smp_mb__before_atomic() is not valid on
atomic_read().

> > 	 *   [S] atomic_inc(used_lists);
> > 	 *       smp_mb__after_atomic();
> >