On Thu, Oct 20, 2016 at 05:00:35PM +0200, Takashi Iwai wrote: > On Thu, 20 Oct 2016 16:56:04 +0200, > Ville Syrjälä 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: <stable@xxxxxxxxxxxxxxx> > > > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> > > > --- > > > 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 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
