drm/i915: Kill the active list spinlock

This spinlock only served debugging purposes in a time when we could not
be sure of the mutex ever being released upon a GPU hang. As we now
should be able rely on hangcheck to do the job for us (and that error
reporting should not itself require the struct mutex) we can kill the
incomplete attempt at protection.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 2 insertions, 33 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index afe4a9b0a03d..b6e4b60724ec 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1486,7 +1486,6 @@ i915_gem_object_move_to_active(struct drm_gem_object *obj,
                                struct intel_ring_buffer *ring)
 {
         struct drm_device *dev = obj->dev;
-        drm_i915_private_t *dev_priv = dev->dev_private;
         struct drm_i915_gem_object *obj_priv = to_intel_bo(obj);
         uint32_t seqno = i915_gem_next_request_seqno(dev, ring);
 
@@ -1500,9 +1499,7 @@ i915_gem_object_move_to_active(struct drm_gem_object *obj,
         }
 
         /* Move from whatever list we were on to the tail of execution. */
-        spin_lock(&dev_priv->mm.active_list_lock);
         list_move_tail(&obj_priv->list, &ring->active_list);
-        spin_unlock(&dev_priv->mm.active_list_lock);
         obj_priv->last_rendering_seqno = seqno;
 }
 
@@ -1676,14 +1673,11 @@ static void
 i915_gem_retire_request(struct drm_device *dev,
                         struct drm_i915_gem_request *request)
 {
-        drm_i915_private_t *dev_priv = dev->dev_private;
-
         trace_i915_gem_request_retire(dev, request->seqno);
 
         /* Move any buffers on the active list that are no longer referenced
          * by the ringbuffer to the flushing/inactive lists as appropriate.
          */
-        spin_lock(&dev_priv->mm.active_list_lock);
         while (!list_empty(&request->ring->active_list)) {
                 struct drm_gem_object *obj;
                 struct drm_i915_gem_object *obj_priv;
@@ -1698,7 +1692,7 @@ i915_gem_retire_request(struct drm_device *dev,
                  * this seqno.
                  */
                 if (obj_priv->last_rendering_seqno != request->seqno)
-                        goto out;
+                        return;
 
 #if WATCH_LRU
                 DRM_INFO("%s: retire %d moves to inactive list %p\n",
@@ -1707,22 +1701,9 @@ i915_gem_retire_request(struct drm_device *dev,
 
                 if (obj->write_domain != 0)
                         i915_gem_object_move_to_flushing(obj);
-                else {
-                        /* Take a reference on the object so it won't be
-                         * freed while the spinlock is held.  The list
-                         * protection for this spinlock is safe when breaking
-                         * the lock like this since the next thing we do
-                         * is just get the head of the list again.
-                         */
-                        drm_gem_object_reference(obj);
+                else
                         i915_gem_object_move_to_inactive(obj);
-                        spin_unlock(&dev_priv->mm.active_list_lock);
-                        drm_gem_object_unreference(obj);
-                        spin_lock(&dev_priv->mm.active_list_lock);
-                }
         }
-out:
-        spin_unlock(&dev_priv->mm.active_list_lock);
 }
 
 /**
@@ -1972,7 +1953,6 @@ int
 i915_gem_object_unbind(struct drm_gem_object *obj)
 {
         struct drm_device *dev = obj->dev;
-        drm_i915_private_t *dev_priv = dev->dev_private;
         struct drm_i915_gem_object *obj_priv = to_intel_bo(obj);
         int ret = 0;
 
@@ -2027,10 +2007,8 @@ i915_gem_object_unbind(struct drm_gem_object *obj)
         }
 
         /* Remove ourselves from the LRU list if present. */
-        spin_lock(&dev_priv->mm.active_list_lock);
         if (!list_empty(&obj_priv->list))
                 list_del_init(&obj_priv->list);
-        spin_unlock(&dev_priv->mm.active_list_lock);
 
         if (i915_gem_object_is_purgeable(obj_priv))
                 i915_gem_object_truncate(obj);
@@ -2047,13 +2025,10 @@ i915_gpu_idle(struct drm_device *dev)
         bool lists_empty;
         int ret;
 
-        spin_lock(&dev_priv->mm.active_list_lock);
         lists_empty = (list_empty(&dev_priv->mm.flushing_list) &&
                        list_empty(&dev_priv->render_ring.active_list) &&
                        (!HAS_BSD(dev) ||
                         list_empty(&dev_priv->bsd_ring.active_list)));
-        spin_unlock(&dev_priv->mm.active_list_lock);
-
         if (lists_empty)
                 return 0;
 
@@ -4550,11 +4525,8 @@ i915_gem_entervt_ioctl(struct drm_device *dev, void *data,
                 return ret;
         }
 
-        spin_lock(&dev_priv->mm.active_list_lock);
         BUG_ON(!list_empty(&dev_priv->render_ring.active_list));
         BUG_ON(HAS_BSD(dev) && !list_empty(&dev_priv->bsd_ring.active_list));
-        spin_unlock(&dev_priv->mm.active_list_lock);
-
         BUG_ON(!list_empty(&dev_priv->mm.flushing_list));
         BUG_ON(!list_empty(&dev_priv->mm.inactive_list));
         BUG_ON(!list_empty(&dev_priv->render_ring.request_list));
@@ -4606,7 +4578,6 @@ i915_gem_load(struct drm_device *dev)
         int i;
         drm_i915_private_t *dev_priv = dev->dev_private;
 
-        spin_lock_init(&dev_priv->mm.active_list_lock);
         INIT_LIST_HEAD(&dev_priv->mm.flushing_list);
         INIT_LIST_HEAD(&dev_priv->mm.gpu_write_list);
         INIT_LIST_HEAD(&dev_priv->mm.inactive_list);
@@ -4862,12 +4833,10 @@ i915_gpu_is_active(struct drm_device *dev)
         drm_i915_private_t *dev_priv = dev->dev_private;
         int lists_empty;
 
-        spin_lock(&dev_priv->mm.active_list_lock);
         lists_empty = list_empty(&dev_priv->mm.flushing_list) &&
                       list_empty(&dev_priv->render_ring.active_list);
         if (HAS_BSD(dev))
                 lists_empty &= list_empty(&dev_priv->bsd_ring.active_list);
-        spin_unlock(&dev_priv->mm.active_list_lock);
 
         return !lists_empty;
 }