drm/i915: Drop the deferred active reference

An old optimisation to reduce the number of atomics per batch sadly
relies on struct_mutex for coordination. In order to remove struct_mutex
from serialising object/context closing, always taking and releasing an
active reference on first use / last use greatly simplifies the locking.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528092956.14910-15-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/selftests/huge_pages.c

@@ -976,8 +976,6 @@ static int gpu_write(struct i915_vma *vma,
 	if (err)
 		goto err_request;
 
-	i915_gem_object_set_active_reference(batch->obj);
-
 	i915_vma_lock(vma);
 	err = i915_gem_object_set_to_gtt_domain(vma->obj, false);
 	if (err == 0)
@@ -996,6 +994,7 @@ err_request:
 err_batch:
 	i915_vma_unpin(batch);
 	i915_vma_close(batch);
+	i915_vma_put(batch);
 
 	return err;
 }

drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c

@@ -365,7 +365,7 @@ static int igt_gem_coherency(void *arg)
 						}
 					}
 
-					__i915_gem_object_release_unless_active(obj);
+					i915_gem_object_put(obj);
 				}
 			}
 		}
@@ -377,7 +377,7 @@ unlock:
 	return err;
 
 put_object:
-	__i915_gem_object_release_unless_active(obj);
+	i915_gem_object_put(obj);
 	goto unlock;
 }
 

drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c

@@ -318,14 +318,14 @@ static int gpu_fill(struct drm_i915_gem_object *obj,
 	if (err)
 		goto skip_request;
 
-	i915_gem_object_set_active_reference(batch->obj);
+	i915_request_add(rq);
+
 	i915_vma_unpin(batch);
 	i915_vma_close(batch);
+	i915_vma_put(batch);
 
 	i915_vma_unpin(vma);
 
-	i915_request_add(rq);
-
 	return 0;
 
 skip_request:
@@ -802,9 +802,9 @@ emit_rpcs_query(struct drm_i915_gem_object *obj,
 	if (err)
 		goto skip_request;
 
-	i915_gem_object_set_active_reference(batch->obj);
 	i915_vma_unpin(batch);
 	i915_vma_close(batch);
+	i915_vma_put(batch);
 
 	i915_vma_unpin(vma);
 
@@ -820,6 +820,7 @@ err_request:
 	i915_request_add(rq);
 err_batch:
 	i915_vma_unpin(batch);
+	i915_vma_put(batch);
 err_vma:
 	i915_vma_unpin(vma);
 
@@ -1365,9 +1366,9 @@ static int write_to_scratch(struct i915_gem_context *ctx,
 	if (err)
 		goto skip_request;
 
-	i915_gem_object_set_active_reference(obj);
 	i915_vma_unpin(vma);
 	i915_vma_close(vma);
+	i915_vma_put(vma);
 
 	i915_request_add(rq);
 

drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c

@@ -354,8 +354,8 @@ static int make_obj_busy(struct drm_i915_gem_object *obj)
 
 	i915_request_add(rq);
 
-	__i915_gem_object_release_unless_active(obj);
 	i915_vma_unpin(vma);
+	i915_gem_object_put(obj); /* leave it only alive via its active ref */
 
 	return err;
 }