Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756067AbcC2Hn0 (ORCPT ); Tue, 29 Mar 2016 03:43:26 -0400 Received: from mail-ob0-f169.google.com ([209.85.214.169]:32771 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751867AbcC2HnX (ORCPT ); Tue, 29 Mar 2016 03:43:23 -0400 MIME-Version: 1.0 X-Originating-IP: [2a02:168:56b5:0:ac27:b86c:7764:9429] In-Reply-To: References: Date: Tue, 29 Mar 2016 09:43:22 +0200 Message-ID: Subject: Re: i915 4.5 bugfix backport and release management issue? From: Daniel Vetter To: Andy Lutomirski Cc: DRI , Dave Airlie , Matt Roper , Jani Nikula , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2358 Lines: 57 On Tue, Mar 29, 2016 at 4:39 AM, Andy Lutomirski wrote: > AFAICT something got rather screwed up in i915 land for 4.5. > > $ git log --oneline --grep='Pretend cursor is always on' v4.5 > drivers/gpu/drm/i915/ > e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM > calculations (v2) > > $ git log --oneline --grep='Pretend cursor is always on' v4.6-rc1 > drivers/gpu/drm/i915/ > e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM > calculations (v2) > b2435692dbb7 drm/i915: Pretend cursor is always on for ILK-style WM > calculations (v2) > > The two patches there are almost, but not quite, the same thing, which > makes me wonder how they both ended up in Linus' tree without an > obvious merge conflict. > > I have no idea what caused this. However, I think (on very little > inspection, but it's consistent with problems I have with 4.5 on my > laptop) that the first one is an *incorrect* fix for a regression in > 4.5 and the second is a correct fix for the same regression. 4.6-rc1 > seems okay. > > I reported the regression and everyone involved has known about it for > weeks. Nonetheless, 4.5 final is busted. Quoting from e2e407dc093f "(cherry picked from commit b2435692dbb709d4c8ff3b2f2815c9b8423b72bb)" i.e. this is intentionally twice in the history. We started to soak bugfixes in -next and then cherry pick them because we had too much fun with things blowing up, and also too much fun with really messy conflicts. It's not a botched patch in 4.5 or anything else nefarious at all. Which just means that there's another bugfix in 4.6-rc1 that needs to be backported to 4.5 but hasn't arrived in there yet. Two possible cases: - Greg is too slow with cc: stable patches - especially around releases we occasionally put the patch into the wrong branch at first, or it simply misses the last pull. 4.6 closes for drm drivers already at 4.5-rc5, so there's a sizeable overlap where placing patches correctly requires some juggling. - We've genuinely failed to cherry-pick a bugfix over. It happens, despite our best efforts (which of course includes running stuff on Linus' tree). Please do a reverse bisect so we know which precise commit fell through the cracks. Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch