ff811ebcf2>] drm_fb_helper_restore+0x9/0x24
[   54.625717]  [<ffffffff81290a41>] i915_driver_lastclose+0x2b/0x5c
[   54.625720]  [<ffffffff811f14a7>] drm_lastclose+0x44/0x2ad
[   54.625722]  [<ffffffff811f1ed2>] drm_release+0x5c6/0x609
[   54.625726]  [<ffffffff810d1275>] fput+0x109/0x1c7
[   54.625728]  [<ffffffff810ce5e4>] filp_close+0x61/0x6b
[   54.625731]  [<ffffffff810ce680>] sys_close+0x92/0xd4
[   54.625734]  [<ffffffff81002a2b>] system_call_fastpath+0x16/0x1b

v2: The spinlock is actually superfluous as access to open_count is
entirely serialised by drm_global_mutex and so can be dropped. The
count_lock spinlock instead appears to be used to protect access to
dev->buf_alloc and dev->buf_use.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>