drm/i915: Provide an i915_active.acquire callback

If we introduce a callback for i915_active that is only called the first
time we use the i915_active and is symmetrically paired with the
i915_active.retire callback, we can replace the open-coded and
non-atomic implementations -- which will be very fragile (i.e. broken)
upon removing the struct_mutex serialisation.

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/20190621183801.23252-4-chris@chris-wilson.co.uk

1 files changed, 42 insertions, 11 deletions

diff --git a/drivers/gpu/drm/i915/selftests/i915_active.c b/drivers/gpu/drm/i915/selftests/i915_active.c
index 98493bcc91f2..84fce379c0de 100644
--- a/drivers/gpu/drm/i915/selftests/i915_active.c
+++ b/drivers/gpu/drm/i915/selftests/i915_active.c
@@ -4,6 +4,8 @@
  * Copyright © 2018 Intel Corporation
  */
 
+#include <linux/kref.h>
+
 #include "gem/i915_gem_pm.h"
 
 #include "i915_selftest.h"
@@ -13,20 +15,47 @@
 
 struct live_active {
 	struct i915_active base;
+	struct kref ref;
 	bool retired;
 };
 
+static void __live_get(struct live_active *active)
+{
+	kref_get(&active->ref);
+}
+
 static void __live_free(struct live_active *active)
 {
 	i915_active_fini(&active->base);
 	kfree(active);
 }
 
+static void __live_release(struct kref *ref)
+{
+	struct live_active *active = container_of(ref, typeof(*active), ref);
+
+	__live_free(active);
+}
+
+static void __live_put(struct live_active *active)
+{
+	kref_put(&active->ref, __live_release);
+}
+
+static int __live_active(struct i915_active *base)
+{
+	struct live_active *active = container_of(base, typeof(*active), base);
+
+	__live_get(active);
+	return 0;
+}
+
 static void __live_retire(struct i915_active *base)
 {
 	struct live_active *active = container_of(base, typeof(*active), base);
 
 	active->retired = true;
+	__live_put(active);
 }
 
 static struct live_active *__live_alloc(struct drm_i915_private *i915)
@@ -37,7 +66,8 @@ static struct live_active *__live_alloc(struct drm_i915_private *i915)
 	if (!active)
 		return NULL;
 
-	i915_active_init(i915, &active->base, __live_retire);
+	kref_init(&active->ref);
+	i915_active_init(i915, &active->base, __live_active, __live_retire);
 
 	return active;
 }
@@ -62,11 +92,9 @@ __live_active_setup(struct drm_i915_private *i915)
 		return ERR_PTR(-ENOMEM);
 	}
 
-	if (!i915_active_acquire(&active->base)) {
-		pr_err("First i915_active_acquire should report being idle\n");
-		err = -EINVAL;
+	err = i915_active_acquire(&active->base);
+	if (err)
 		goto out;
-	}
 
 	for_each_engine(engine, i915, id) {
 		struct i915_request *rq;
@@ -97,18 +125,21 @@ __live_active_setup(struct drm_i915_private *i915)
 		pr_err("i915_active retired before submission!\n");
 		err = -EINVAL;
 	}
-	if (active->base.count != count) {
+	if (atomic_read(&active->base.count) != count) {
 		pr_err("i915_active not tracking all requests, found %d, expected %d\n",
-		       active->base.count, count);
+		       atomic_read(&active->base.count), count);
 		err = -EINVAL;
 	}
 
 out:
 	i915_sw_fence_commit(submit);
 	heap_fence_put(submit);
+	if (err) {
+		__live_put(active);
+		active = ERR_PTR(err);
+	}
 
-	/* XXX leaks live_active on error */
-	return err ? ERR_PTR(err) : active;
+	return active;
 }
 
 static int live_active_wait(void *arg)
@@ -135,7 +166,7 @@ static int live_active_wait(void *arg)
 		err = -EINVAL;
 	}
 
-	__live_free(active);
+	__live_put(active);
 
 	if (igt_flush_test(i915, I915_WAIT_LOCKED))
 		err = -EIO;
@@ -174,7 +205,7 @@ static int live_active_retire(void *arg)
 		err = -EINVAL;
 	}
 
-	__live_free(active);
+	__live_put(active);
 
 err:
 	intel_runtime_pm_put(&i915->runtime_pm, wakeref);