On Thu, Dec 15, 2016 at 06:01:10AM +0100, Jason A. Donenfeld wrote: > On most platforms, there exists this ifdef: > > #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0) > > This makes this patch functionally useless. However, on PPC, there is > actually an explicit definition of atomic_inc_not_zero with its own > assembly that is slightly more optimized than atomic_add_unless. So, > this patch changes kref to use atomic_inc_not_zero instead, for PPC and > any future platforms that might provide an explicit implementation. > > This also puts this usage of kref more in line with a verbatim reading > of the examples in Paul McKenney's paper [1] in the section titled "2.4 > Atomic Counting With Check and Release Memory Barrier", which uses > atomic_inc_not_zero. > > [1] http://open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2167.pdf > > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> > Reviewed-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx> Applied to drm-misc, but for 4.11 since 4.10 is bugfixes only already. Thanks, Daniel > --- > This was reviewed favorably 14 months ago but never picked up. > I'm resubmitting it now in hopes that you can finally queue it > up for 4.10. > > include/linux/kref.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/kref.h b/include/linux/kref.h > index e15828fd71f1..62f0a84ae94e 100644 > --- a/include/linux/kref.h > +++ b/include/linux/kref.h > @@ -133,6 +133,6 @@ static inline int kref_put_mutex(struct kref *kref, > */ > static inline int __must_check kref_get_unless_zero(struct kref *kref) > { > - return atomic_add_unless(&kref->refcount, 1, 0); > + return atomic_inc_not_zero(&kref->refcount); > } > #endif /* _KREF_H_ */ > -- > 2.11.0 > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
