From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751735AbcF2WwR (ORCPT ); Wed, 29 Jun 2016 18:52:17 -0400 Received: from frisell.zx2c4.com ([192.95.5.64]:47197 "EHLO frisell.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751480AbcF2WwQ convert rfc822-to-8bit (ORCPT ); Wed, 29 Jun 2016 18:52:16 -0400 MIME-Version: 1.0 In-Reply-To: References: <1444474594-28359-1-git-send-email-Jason@zx2c4.com> <561ABFA6.8050102@vmware.com> From: "Jason A. Donenfeld" Date: Thu, 30 Jun 2016 00:52:02 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless To: Thomas Hellstrom , Dave Airlie Cc: LKML , Paul McKenney Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This was positively reviewed by maintainers but never picked up. Can someone queue this for 4.7 or 4.8? Thanks, Jason On Mon, Feb 1, 2016 at 10:53 PM, Jason A. Donenfeld wrote: > This was positively reviewed but never picked up. Can someone queue > this for rc3? > > Thanks, > Jason > > On Sun, Oct 11, 2015 at 9:59 PM, Thomas Hellstrom wrote: >> Reviewed-by: Thomas Hellstrom >> >> >> 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 >>> --- >>> 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_ */ >>