drm/i915: Track i915_active using debugobjects

Provide runtime asserts and tracking of i915_active via debugobjects.
For example, this should allow us to check that the i915_active is only
active when we expect it to be and is never freed too early.

One consequence is that, for simplicity, we no longer allow i915_active
to be on-stack which only affected the selftests.

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/20190621183801.23252-2-chris@chris-wilson.co.uk

1 files changed, 65 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index 293e5bcc4b6c..eb91a625c71f 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -4,6 +4,8 @@
  * Copyright © 2019 Intel Corporation
  */
 
+#include <linux/debugobjects.h>
+
 #include "gt/intel_engine_pm.h"
 
 #include "i915_drv.h"
@@ -31,6 +33,55 @@ struct active_node {
 	u64 timeline;
 };
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && IS_ENABLED(CONFIG_DEBUG_OBJECTS)
+
+static void *active_debug_hint(void *addr)
+{
+	struct i915_active *ref = addr;
+
+	return (void *)ref->retire ?: (void *)ref;
+}
+
+static struct debug_obj_descr active_debug_desc = {
+	.name = "i915_active",
+	.debug_hint = active_debug_hint,
+};
+
+static void debug_active_init(struct i915_active *ref)
+{
+	debug_object_init(ref, &active_debug_desc);
+}
+
+static void debug_active_activate(struct i915_active *ref)
+{
+	debug_object_activate(ref, &active_debug_desc);
+}
+
+static void debug_active_deactivate(struct i915_active *ref)
+{
+	debug_object_deactivate(ref, &active_debug_desc);
+}
+
+static void debug_active_fini(struct i915_active *ref)
+{
+	debug_object_free(ref, &active_debug_desc);
+}
+
+static void debug_active_assert(struct i915_active *ref)
+{
+	debug_object_assert_init(ref, &active_debug_desc);
+}
+
+#else
+
+static inline void debug_active_init(struct i915_active *ref) { }
+static inline void debug_active_activate(struct i915_active *ref) { }
+static inline void debug_active_deactivate(struct i915_active *ref) { }
+static inline void debug_active_fini(struct i915_active *ref) { }
+static inline void debug_active_assert(struct i915_active *ref) { }
+
+#endif
+
 static void
 __active_park(struct i915_active *ref)
 {
@@ -50,6 +101,8 @@ __active_retire(struct i915_active *ref)
 	if (--ref->count)
 		return;
 
+	debug_active_deactivate(ref);
+
 	/* return the unused nodes to our slabcache */
 	__active_park(ref);
 
@@ -155,6 +208,8 @@ void i915_active_init(struct drm_i915_private *i915,
 		      struct i915_active *ref,
 		      void (*retire)(struct i915_active *ref))
 {
+	debug_active_init(ref);
+
 	ref->i915 = i915;
 	ref->retire = retire;
 	ref->tree = RB_ROOT;
@@ -191,13 +246,21 @@ out:
 
 bool i915_active_acquire(struct i915_active *ref)
 {
+	debug_active_assert(ref);
 	lockdep_assert_held(BKL(ref));
-	return !ref->count++;
+
+	if (ref->count++)
+		return false;
+
+	debug_active_activate(ref);
+	return true;
 }
 
 void i915_active_release(struct i915_active *ref)
 {
+	debug_active_assert(ref);
 	lockdep_assert_held(BKL(ref));
+
 	__active_retire(ref);
 }
 
@@ -260,6 +323,7 @@ out:
 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
 void i915_active_fini(struct i915_active *ref)
 {
+	debug_active_fini(ref);
 	GEM_BUG_ON(i915_active_request_isset(&ref->last));
 	GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
 	GEM_BUG_ON(ref->count);