[Nouveau] NVAC: WARN_ON(nvbo->pin_refcnt > 0);

[poma]

[...]
> WARNING: CPU: 1 PID: 701 at drivers/gpu/drm/nouveau/nouveau_bo.c:137 nouveau_bo_del_ttm+0x7f/0x90 [nouveau]
[...]

Which does not appear within mainline 4.10,
tested with 4.10.0-1.fc26.x86_64+debug.

OK