drm/i915: Check to see if we've pinned all available fences

We need to check and report if there are no available fences - or else we
spin endlessly waiting for a buffer to magically unpin itself.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 10 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 12c7d78d9240..2b5c7ad9e64a 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1557,7 +1557,8 @@ i915_gem_object_get_fence_reg(struct drm_gem_object *obj, bool write)
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct drm_i915_gem_object *obj_priv = obj->driver_private;
         struct drm_i915_fence_reg *reg = NULL;
-        int i, ret;
+        struct drm_i915_gem_object *old_obj_priv = NULL;
+        int i, ret, avail;
 
         switch (obj_priv->tiling_mode) {
         case I915_TILING_NONE:
@@ -1581,17 +1582,24 @@ i915_gem_object_get_fence_reg(struct drm_gem_object *obj, bool write)
 
         /* First try to find a free reg */
 try_again:
+        avail = 0;
         for (i = dev_priv->fence_reg_start; i < dev_priv->num_fence_regs; i++) {
                 reg = &dev_priv->fence_regs[i];
                 if (!reg->obj)
                         break;
+
+                old_obj_priv = reg->obj->driver_private;
+                if (!old_obj_priv->pin_count)
+                    avail++;
         }
 
         /* None available, try to steal one or wait for a user to finish */
         if (i == dev_priv->num_fence_regs) {
-                struct drm_i915_gem_object *old_obj_priv = NULL;
                 loff_t offset;
 
+                if (avail == 0)
+                        return -ENOMEM;
+
                 /* Could try to use LRU here instead... */
                 for (i = dev_priv->fence_reg_start;
                      i < dev_priv->num_fence_regs; i++) {