Re: [Linaro-mm-sig] [PATCH 1/8] dma-buf: fix busy wait for new shared fences

Quoting Christian König (2019-08-06 16:01:27)

When reservation_object_add_shared_fence is replacing an old fence with a new one we should not drop the old one before the new one is in place.

Otherwise other cores can busy wait for the new one to appear.

I see. The reader will see a refcount==0 fence and restart, whereas by dropping the ref later, that reader has a better chance of getting to the end before noticing the change.

Signed-off-by: Christian König christian.koenig@amd.com

Reviewed-by: Chris Wilson chris@chris-wilson.co.uk -Chris