Reviewed-by: Thomas Hellstrom <thellst...@vmware.com>
On 10/10/2015 12:56 PM, 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] > https://urldefense.proofpoint.com/v2/url?u=http-3A__open-2Dstd.org_jtc1_sc22_wg21_docs_papers_2007_n2167.pdf&d=BQIBAg&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=vpukPkBtpoNQp2IUKuFviOmPNYWVKmen3Jeeu55zmEA&m=z5Nd9sYiJMKiphNjyZp6XT5CbayXMBlcb903f260pDY&s=HEHX3CuXRs2GRRQWuC4Vef6iJMwdilKVRkiZgJpjEpA&e= > > > Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com> > --- > 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 484604d..83d1f94 100644 > --- a/include/linux/kref.h > +++ b/include/linux/kref.h > @@ -166,6 +166,6 @@ 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_ */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/