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>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 12c7d78d92402430052a460cd3fa21cdae67ec23..2b5c7ad9e64a89d9492cb7ef173588429880a191 100644 (file)
--- 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++) {