Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752103AbdFTJao (ORCPT ); Tue, 20 Jun 2017 05:30:44 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:36690 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751098AbdFTJ3g (ORCPT ); Tue, 20 Jun 2017 05:29:36 -0400 Date: Tue, 20 Jun 2017 11:29:21 +0200 From: Daniel Vetter To: Andrey Grodzovsky Cc: Sean Paul , Harry Wentland , intel-gfx@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [Intel-gfx] [PATCH] drm/core: Fail atomic IOCTL with no CRTC state but with signaling. Message-ID: <20170620092921.hk5dofw2v52b3s7b@phenom.ffwll.local> Mail-Followup-To: Andrey Grodzovsky , Sean Paul , Harry Wentland , intel-gfx@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <1497043819-28591-1-git-send-email-Andrey.Grodzovsky@amd.com> <0d603149-3fb0-3d48-89e5-77e3f7686415@amd.com> <20170619192431.tbsntjjdkianx2kc@art_vandelay> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux phenom 4.9.0-2-amd64 User-Agent: NeoMutt/20170306 (1.8.0) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4615 Lines: 125 On Mon, Jun 19, 2017 at 04:11:35PM -0400, Andrey Grodzovsky wrote: > > > On 06/19/2017 03:24 PM, Sean Paul wrote: > > On Mon, Jun 19, 2017 at 11:35:28AM -0400, Harry Wentland wrote: > > > On 2017-06-09 05:30 PM, Andrey Grodzovsky wrote: > > > > Problem: > > > > While running IGT kms_atomic_transition test suite i encountered > > > > a hang in drmHandleEvent immidietly follwoing an atomic_commit. > > > s/immidietly/immediately/g > > > s/follwoing/following/g > > > > > > > After dumping the atomic state I relized that in this case there was > > > > not even one CRTC attached to the state and only disabled > > > > planes. This probably due to a commit which hadn't changed any property > > > > which would require attaching crtc state. This means drmHandleEvent > > > > will never wake up from read since without CRTC in atomic state > > > > the event fd will not be singnaled. > > > s/singnaled/signaled/g > > > > > > > This point to a bug in IGT but also DRM should gracefully > > > > fail such scenario so no hang on user side will happen. > > > > > > > Can we create an IGT fix for this to make sure this won't happen? > > > > > > > Fix: > > > > Explicitly fail by failing atomic_commit early in > > > > drm_mode_atomic_commit where such problem can be identified. > > > > > > > The change seems reasonable to me but I would like to see some input > > > from someone who's more familiar with the usermode side of things. > > I wonder if there's ever a case where it might be desirable to generate an event > > from a commit without a crtc. I don't know if anyone has explicitly said that an > > event can only be generated from state with crtc. > For a generic event i agree, bit seems to me without active CRTC no way you > can expect PAGE_FLIP_EVENT to fire. > > > > I usually don't mind letting userspace shoot itself in the foot, so keep that in > > mind :) > > > > Sean > > Seems to me you still would try to avoid a bad configuration, returning > error > will help debugging for user who made a mistake. I also see something > similar > in drm_mode_atomic_ioctl around line 2122 - > > /* can't test and expect an event at the same time. */ > if ((arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) && > (arg->flags & DRM_MODE_PAGE_FLIP_EVENT)) > return -EINVAL; Asking for an event without anything changed is a bug imo. We need to fix the testcases, and even better would be to have an explicit testcase which does such a no-op atomic ioctl + event and checks that we get the -EINVAL. Same applies for asking for events when the crtc is off and stays off btw, but I think we catch that already somewhere. But again would be good to make sure we have an igt for it. Thanks, Daniel > > Thanks, > Andrey > > > > Signed-off-by: Andrey Grodzovsky > > > > --- > > > > drivers/gpu/drm/drm_atomic.c | 13 ++++++++++++- > > > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c > > > > index a567310..32eae1c 100644 > > > > --- a/drivers/gpu/drm/drm_atomic.c > > > > +++ b/drivers/gpu/drm/drm_atomic.c > > > > @@ -1933,7 +1933,7 @@ static int prepare_crtc_signaling(struct drm_device *dev, > > > > { > > > > struct drm_crtc *crtc; > > > > struct drm_crtc_state *crtc_state; > > > > - int i, ret; > > > > + int i, c = 0, ret; > > > > if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) > > > > return 0; > > > > @@ -1994,8 +1994,17 @@ static int prepare_crtc_signaling(struct drm_device *dev, > > > > crtc_state->event->base.fence = fence; > > > > } > > > > + > > > > + c++; > > > Not sure if intentional, but I like it. > > > > > > > } > > > > + /* > > > > + * Having this flag means user mode pends on event which will never > > > > + * reach due to lack of at least one CRTC for signaling > > > > + */ > > > > + if (c == 0 && (arg->flags & DRM_MODE_PAGE_FLIP_EVENT)) > > > > + return -EINVAL; > > > > + > > > > return 0; > > > > } > > > > @@ -2179,6 +2188,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev, > > > > drm_mode_object_unreference(obj); > > > > } > > > > + > > > > + > > > Remove these extraneous newlines. > > > > > > Harry > > > > > > > ret = prepare_crtc_signaling(dev, state, arg, file_priv, &fence_state, > > > > &num_fences); > > > > if (ret) > > > > > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch