[PATCH] dma-buf/sync_file: Allow multiple sync_files to wrap a single dma-fence

[Daniel Vetter]

On Sat, Jul 29, 2017 at 12:18:32PM -0300, Gustavo Padovan wrote:
> Hi Chris,
> 
> 2017-07-28 Chris Wilson <chris at chris-wilson.co.uk>:
> 
> > Up until recently sync_file were create to export a single dma-fence to
> > userspace, and so we could canabalise a bit insie dma-fence to mark
> > whether or not we had enable polling for the sync_file itself. However,
> > with the advent of syncobj, we do allow userspace to create multiple
> > sync_files for a single dma-fence. (Similarly, that the sw-sync
> > validation framework also started returning multiple sync-files wrapping
> > a single dma-fence for a syncpt also triggering the problem.)
> > 
> > This patch reverts my suggestion in commit e24165537312
> > ("dma-buf/sync_file: only enable fence signalling on poll()") to use a
> > single bit in the shared dma-fence and restores the sync_file->flags for
> > tracking the bits individually.
> > 
> > Reported-by: Gustavo Padovan <gustavo at padovan.org>
> > Fixes: f1e8c67123cf ("dma-buf/sw-sync: Use an rbtree to sort fences in the timeline")
> > Fixes: e9083420bbac ("drm: introduce sync objects (v4)")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Sumit Semwal <sumit.semwal at linaro.org>
> > Cc: Sean Paul <seanpaul at chromium.org>
> > Cc: Gustavo Padovan <gustavo at padovan.org>
> > Cc: dri-devel at lists.freedesktop.org
> > Cc: <drm-intel-fixes at lists.freedesktop.org> # v4.13-rc1+
> > ---
> >  drivers/dma-buf/sync_file.c | 5 +++--
> >  include/linux/sync_file.h   | 3 ++-
> >  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> I confirm the patch fixes the sync kselftests for me. Pushed to
> drm-misc-next.

You need to cherry-pick this to drm-misc-fixes (using cherry-pick -x to
make it clear we applied this twice), since the bug is in 4.13.
drm-misc-next is for stuff that's only needed in 4.14.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch