Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755455AbcJUMai (ORCPT ); Fri, 21 Oct 2016 08:30:38 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:36790 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754464AbcJUMah (ORCPT ); Fri, 21 Oct 2016 08:30:37 -0400 Date: Fri, 21 Oct 2016 14:30:32 +0200 From: Daniel Vetter To: Takashi Iwai Cc: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Daniel Vetter , Noralf =?iso-8859-1?Q?Tr=F8nnes?= , David Airlie Subject: Re: [PATCH] drm/fb-helper: Don't call dirty callback for untouched clips Message-ID: <20161021123032.GZ20761@phenom.ffwll.local> Mail-Followup-To: Takashi Iwai , Ville =?iso-8859-1?Q?Syrj=E4l=E4?= , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Noralf =?iso-8859-1?Q?Tr=F8nnes?= , David Airlie References: <20161020143952.2538-1-tiwai@suse.de> <20161020145604.GW4329@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Operating-System: Linux phenom 4.6.0-1-amd64 User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3194 Lines: 81 On Thu, Oct 20, 2016 at 05:00:35PM +0200, Takashi Iwai wrote: > On Thu, 20 Oct 2016 16:56:04 +0200, > Ville Syrj?l? wrote: > > > > On Thu, Oct 20, 2016 at 04:39:52PM +0200, Takashi Iwai wrote: > > > Since 4.7 kernel, we've seen the error messages like > > > > > > kernel: [TTM] Buffer eviction failed > > > kernel: qxl 0000:00:02.0: object_init failed for (4026540032, 0x00000001) > > > kernel: [drm:qxl_alloc_bo_reserved [qxl]] *ERROR* failed to allocate VRAM BO > > > > > > on QXL when switching and accessing on VT. The culprit was the > > > generic deferred_io code (qxl driver switched to it since 4.7). > > > There is a race between the dirty clip update and the call of > > > callback. > > > > > > In drm_fb_helper_dirty(), the dirty clip is updated in the spinlock, > > > while it kicks off the update worker outside the spinlock. Meanwhile > > > the update worker clears the dirty clip in the spinlock, too. Thus, > > > when drm_fb_helper_dirty() is called concurrently, schedule_work() is > > > called after the clip is cleared in the first worker call. > > > > > > This patch addresses it by validating the clip before calling the > > > dirty fb callback. > > > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98322 > > > Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1003298 > > > Fixes: eaa434defaca ('drm/fb-helper: Add fb_deferred_io support') > > > Cc: > > > Signed-off-by: Takashi Iwai > > > --- > > > drivers/gpu/drm/drm_fb_helper.c | 13 +++++++++---- > > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > > > index 03414bde1f15..d790d205129e 100644 > > > --- a/drivers/gpu/drm/drm_fb_helper.c > > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > > @@ -636,15 +636,20 @@ static void drm_fb_helper_dirty_work(struct work_struct *work) > > > dirty_work); > > > struct drm_clip_rect *clip = &helper->dirty_clip; > > > struct drm_clip_rect clip_copy; > > > + bool dirty; > > > unsigned long flags; > > > > > > spin_lock_irqsave(&helper->dirty_lock, flags); > > > - clip_copy = *clip; > > > - clip->x1 = clip->y1 = ~0; > > > - clip->x2 = clip->y2 = 0; > > > + dirty = (clip->x1 < clip->x2 && clip->y1 < clip->y2); > > > + if (dirty) { > > > + clip_copy = *clip; > > > + clip->x1 = clip->y1 = ~0; > > > + clip->x2 = clip->y2 = 0; > > > + } > > > spin_unlock_irqrestore(&helper->dirty_lock, flags); > > > > > > - helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1); > > > + if (dirty) > > > > Could do it the other way too, ie. just make the copy, and then check the > > copy (can be done after dropping the lock even). Would avoid having to > > add the 'dirty' variable. > > Sounds good. Let me try... Another thing: How do we prevent userspace from doing the same, i.e. submitting an empty rectangle? Do we need to patch up drm_mode_dirtyfb_ioctl too? Not much point if we fix this bug in the fb helpers and leave the barn door wide open for userspace to oops drivers ;-) -Daniel > > > Takashi -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch