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

[Gustavo Padovan]

2017-07-31 Daniel Vetter <daniel at ffwll.ch>:

> 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

Pushed to drm-misc-fixes now.

	Gustavo