From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757162AbcLPHgx (ORCPT ); Fri, 16 Dec 2016 02:36:53 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:35321 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753839AbcLPHgp (ORCPT ); Fri, 16 Dec 2016 02:36:45 -0500 Date: Fri, 16 Dec 2016 08:36:32 +0100 From: Daniel Vetter To: Greg KH Cc: "Jason A. Donenfeld" , Christoph Hellwig , Thomas Hellstrom , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Daniel Vetter Subject: Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless Message-ID: <20161216073632.ma3fqcjhgzfyebog@phenom.ffwll.local> Mail-Followup-To: Greg KH , "Jason A. Donenfeld" , Christoph Hellwig , Thomas Hellstrom , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20161215185554.21931-1-Jason@zx2c4.com> <20161215191049.GB19707@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161215191049.GB19707@kroah.com> X-Operating-System: Linux phenom 4.8.0-1-amd64 User-Agent: NeoMutt/20161126 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 15, 2016 at 11:10:49AM -0800, Greg KH wrote: > On Thu, Dec 15, 2016 at 07:55:54PM +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 > > Reviewed-by: Thomas Hellstrom > > Reviewed-by: Christoph Hellwig > > --- > > Sorry to submit this again, but people keep reviewing it saying it's fine, > > but then point to somebody else to actually merge this. At the end of the > > chain of fingerpointing is usually Greg. "Just have Greg do it." At this > > point I'm confused, but it's certainly been sufficiently reviewed and > > accepted. So can one of you just respond saying "I'll take it!" > > Well, the crazies over in drm land were the ones that merged this new > api, so they should be the ones responsible for it. But that was way > back in 2012, odds are they don't remember it given the lunacy that is > their subsystem... We do, it's just that I couldn't find Jason's patch when Thomas reviewed it and asked for a resend and it took Jason a while to do that ... Maybe we even remember this api way too well, we're constantly adding new users of it in drm ;-) > I'll take it after 4.10-rc1 is out, thanks. Oh, here's another resubmission of this patch. I've already applied this to my 4.11 queue, will show up in linux-next as soon as -rc1 is out. Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless Date: Fri, 16 Dec 2016 08:36:32 +0100 Message-ID: <20161216073632.ma3fqcjhgzfyebog@phenom.ffwll.local> References: <20161215185554.21931-1-Jason@zx2c4.com> <20161215191049.GB19707@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from mail-wm0-x241.google.com (mail-wm0-x241.google.com [IPv6:2a00:1450:400c:c09::241]) by gabe.freedesktop.org (Postfix) with ESMTPS id 167DD6EB12 for ; Fri, 16 Dec 2016 07:36:37 +0000 (UTC) Received: by mail-wm0-x241.google.com with SMTP id g23so3472657wme.1 for ; Thu, 15 Dec 2016 23:36:36 -0800 (PST) Content-Disposition: inline In-Reply-To: <20161215191049.GB19707@kroah.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Greg KH Cc: "Jason A. Donenfeld" , Thomas Hellstrom , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Christoph Hellwig List-Id: dri-devel@lists.freedesktop.org T24gVGh1LCBEZWMgMTUsIDIwMTYgYXQgMTE6MTA6NDlBTSAtMDgwMCwgR3JlZyBLSCB3cm90ZToK PiBPbiBUaHUsIERlYyAxNSwgMjAxNiBhdCAwNzo1NTo1NFBNICswMTAwLCBKYXNvbiBBLiBEb25l bmZlbGQgd3JvdGU6Cj4gPiBPbiBtb3N0IHBsYXRmb3JtcywgdGhlcmUgZXhpc3RzIHRoaXMgaWZk ZWY6Cj4gPiAKPiA+ICAjZGVmaW5lIGF0b21pY19pbmNfbm90X3plcm8odikgYXRvbWljX2FkZF91 bmxlc3MoKHYpLCAxLCAwKQo+ID4gCj4gPiBUaGlzIG1ha2VzIHRoaXMgcGF0Y2ggZnVuY3Rpb25h bGx5IHVzZWxlc3MuIEhvd2V2ZXIsIG9uIFBQQywgdGhlcmUgaXMKPiA+IGFjdHVhbGx5IGFuIGV4 cGxpY2l0IGRlZmluaXRpb24gb2YgYXRvbWljX2luY19ub3RfemVybyB3aXRoIGl0cyBvd24KPiA+ IGFzc2VtYmx5IHRoYXQgaXMgc2xpZ2h0bHkgbW9yZSBvcHRpbWl6ZWQgdGhhbiBhdG9taWNfYWRk X3VubGVzcy4gU28sCj4gPiB0aGlzIHBhdGNoIGNoYW5nZXMga3JlZiB0byB1c2UgYXRvbWljX2lu Y19ub3RfemVybyBpbnN0ZWFkLCBmb3IgUFBDIGFuZAo+ID4gYW55IGZ1dHVyZSBwbGF0Zm9ybXMg dGhhdCBtaWdodCBwcm92aWRlIGFuIGV4cGxpY2l0IGltcGxlbWVudGF0aW9uLgo+ID4gCj4gPiBU aGlzIGFsc28gcHV0cyB0aGlzIHVzYWdlIG9mIGtyZWYgbW9yZSBpbiBsaW5lIHdpdGggYSB2ZXJi YXRpbSByZWFkaW5nCj4gPiBvZiB0aGUgZXhhbXBsZXMgaW4gUGF1bCBNY0tlbm5leSdzIHBhcGVy IFsxXSBpbiB0aGUgc2VjdGlvbiB0aXRsZWQgIjIuNAo+ID4gQXRvbWljIENvdW50aW5nIFdpdGgg Q2hlY2sgYW5kIFJlbGVhc2UgTWVtb3J5IEJhcnJpZXIiLCB3aGljaCB1c2VzCj4gPiBhdG9taWNf aW5jX25vdF96ZXJvLgo+ID4gCj4gPiBbMV0gaHR0cDovL29wZW4tc3RkLm9yZy9qdGMxL3NjMjIv d2cyMS9kb2NzL3BhcGVycy8yMDA3L24yMTY3LnBkZgo+ID4gCj4gPiBTaWduZWQtb2ZmLWJ5OiBK YXNvbiBBLiBEb25lbmZlbGQgPEphc29uQHp4MmM0LmNvbT4KPiA+IFJldmlld2VkLWJ5OiBUaG9t YXMgSGVsbHN0cm9tIDx0aGVsbHN0cm9tQHZtd2FyZS5jb20+Cj4gPiBSZXZpZXdlZC1ieTogQ2hy aXN0b3BoIEhlbGx3aWcgPGhjaEBsc3QuZGU+Cj4gPiAtLS0KPiA+IFNvcnJ5IHRvIHN1Ym1pdCB0 aGlzIGFnYWluLCBidXQgcGVvcGxlIGtlZXAgcmV2aWV3aW5nIGl0IHNheWluZyBpdCdzIGZpbmUs Cj4gPiBidXQgdGhlbiBwb2ludCB0byBzb21lYm9keSBlbHNlIHRvIGFjdHVhbGx5IG1lcmdlIHRo aXMuIEF0IHRoZSBlbmQgb2YgdGhlCj4gPiBjaGFpbiBvZiBmaW5nZXJwb2ludGluZyBpcyB1c3Vh bGx5IEdyZWcuICJKdXN0IGhhdmUgR3JlZyBkbyBpdC4iIEF0IHRoaXMKPiA+IHBvaW50IEknbSBj b25mdXNlZCwgYnV0IGl0J3MgY2VydGFpbmx5IGJlZW4gc3VmZmljaWVudGx5IHJldmlld2VkIGFu ZAo+ID4gYWNjZXB0ZWQuIFNvIGNhbiBvbmUgb2YgeW91IGp1c3QgcmVzcG9uZCBzYXlpbmcgIkkn bGwgdGFrZSBpdCEiCj4gCj4gV2VsbCwgdGhlIGNyYXppZXMgb3ZlciBpbiBkcm0gbGFuZCB3ZXJl IHRoZSBvbmVzIHRoYXQgbWVyZ2VkIHRoaXMgbmV3Cj4gYXBpLCBzbyB0aGV5IHNob3VsZCBiZSB0 aGUgb25lcyByZXNwb25zaWJsZSBmb3IgaXQuICBCdXQgdGhhdCB3YXMgd2F5Cj4gYmFjayBpbiAy MDEyLCBvZGRzIGFyZSB0aGV5IGRvbid0IHJlbWVtYmVyIGl0IGdpdmVuIHRoZSBsdW5hY3kgdGhh dCBpcwo+IHRoZWlyIHN1YnN5c3RlbS4uLgoKV2UgZG8sIGl0J3MganVzdCB0aGF0IEkgY291bGRu J3QgZmluZCBKYXNvbidzIHBhdGNoIHdoZW4gVGhvbWFzIHJldmlld2VkCml0IGFuZCBhc2tlZCBm b3IgYSByZXNlbmQgYW5kIGl0IHRvb2sgSmFzb24gYSB3aGlsZSB0byBkbyB0aGF0IC4uLgoKTWF5 YmUgd2UgZXZlbiByZW1lbWJlciB0aGlzIGFwaSB3YXkgdG9vIHdlbGwsIHdlJ3JlIGNvbnN0YW50 bHkgYWRkaW5nIG5ldwp1c2VycyBvZiBpdCBpbiBkcm0gOy0pCgo+IEknbGwgdGFrZSBpdCBhZnRl ciA0LjEwLXJjMSBpcyBvdXQsIHRoYW5rcy4KCk9oLCBoZXJlJ3MgYW5vdGhlciByZXN1Ym1pc3Np b24gb2YgdGhpcyBwYXRjaC4gSSd2ZSBhbHJlYWR5IGFwcGxpZWQgdGhpcwp0byBteSA0LjExIHF1 ZXVlLCB3aWxsIHNob3cgdXAgaW4gbGludXgtbmV4dCBhcyBzb29uIGFzIC1yYzEgaXMgb3V0LgoK VGhhbmtzLCBEYW5pZWwKLS0gCkRhbmllbCBWZXR0ZXIKU29mdHdhcmUgRW5naW5lZXIsIEludGVs IENvcnBvcmF0aW9uCmh0dHA6Ly9ibG9nLmZmd2xsLmNoCl9fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fCmRyaS1kZXZlbCBtYWlsaW5nIGxpc3QKZHJpLWRldmVs QGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3RzLmZyZWVkZXNrdG9wLm9yZy9tYWls bWFuL2xpc3RpbmZvL2RyaS1kZXZlbAo=