This is missing in:
commit 
78325f2d270897c9ee0887125b7abb963eb8efea
Author: Ben Widawsky <benjamin.widawsky@intel.com>
Date:   Tue Apr 29 14:52:29 2014 -0700
    drm/i915: Virtualize the ringbuffer signal func
Looks to me like a rebase side-effect...
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
        ring->dispatch_execbuffer =
                        gen8_ring_dispatch_execbuffer;
        ring->semaphore.sync_to = gen6_ring_sync;
+       ring->semaphore.signal = gen6_signal;
        /*
         * The current semaphore is only applied on the pre-gen8. And there
         * is no bsd2 ring on the pre-gen8. So now the semaphore_register