Maarten Lankhorst of Canonical has sent out his latest patch series that adds fence and poll support to DMA_BUF for providing cross-device synchronization support. The DMA-BUF sync support is now up to its 17th patch revision. These latest patches were published this morning and can be found on the dri-devel mailing list.
This work has been ongoing for several months and can lead to reduce tearing and other improvements with being able to synchronize the buffer sharing process between GPU DRM drivers. There's also use-cases in the ARM SoC world too for those using DMA-BUF for sharing of buffers between drivers. It's way too late to see DMA_BUF synchronization for Linux 3.14, but hopefully it will finally be ready in time for the Linux 3.15 kernel in a couple months.