drm/i915: unload: fix retire_work races

ums-gem code correctly cancels the retire work (at lastclose time),
kms does not do so. Fix this by canceling the work right after ideling
the gpu.

While staring at the code I noticed that the work function is not
static. Fix this, too.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_dma.c

@@ -2261,6 +2261,9 @@ int i915_driver_unload(struct drm_device *dev)
 		DRM_ERROR("failed to idle hardware: %d\n", ret);
 	mutex_unlock(&dev->struct_mutex);
 
+	/* Cancel the retire work handler, which should be idle now. */
+	cancel_delayed_work_sync(&dev_priv->mm.retire_work);
+
 	io_mapping_free(dev_priv->mm.gtt_mapping);
 	if (dev_priv->mm.gtt_mtrr >= 0) {
 		mtrr_del(dev_priv->mm.gtt_mtrr, dev->agp->base,

drivers/gpu/drm/i915/i915_drv.h

@@ -978,7 +978,6 @@ bool i915_seqno_passed(uint32_t seq1, uint32_t seq2);
 int i915_gem_object_get_fence_reg(struct drm_gem_object *obj);
 int i915_gem_object_put_fence_reg(struct drm_gem_object *obj);
 void i915_gem_retire_requests(struct drm_device *dev);
-void i915_gem_retire_work_handler(struct work_struct *work);
 void i915_gem_clflush_object(struct drm_gem_object *obj);
 int i915_gem_object_set_domain(struct drm_gem_object *obj,
 			       uint32_t read_domains,

drivers/gpu/drm/i915/i915_gem.c

@@ -1797,7 +1797,7 @@ i915_gem_retire_requests(struct drm_device *dev)
 		i915_gem_retire_requests_ring(dev, &dev_priv->bsd_ring);
 }
 
-void
+static void
 i915_gem_retire_work_handler(struct work_struct *work)
 {
 	drm_i915_private_t *dev_priv;