[PATCH 25/36] drm/i915: Prepare for obj->mm.lock removal

[Maarten Lankhorst]

From: Thomas Hellström <thomas.hellstrom at intel.com>

Signed-off-by: Thomas Hellström <thomas.hellstrom at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.h | 32 ++++++++++++++++++++++
 drivers/gpu/drm/i915/gem/i915_gem_pages.c  | 14 ++++++++--
 drivers/gpu/drm/i915/gem/i915_gem_stolen.c |  4 +++
 3 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index eecbfec4b152..a8f001e35584 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -115,6 +115,25 @@ i915_gem_object_put(struct drm_i915_gem_object *obj)
 
 #define assert_object_held(obj) dma_resv_assert_held((obj)->base.resv)
 
+/*
+ * If more than one potential simultaneous locker, assert held.
+ */
+static inline void assert_object_held_shared(struct drm_i915_gem_object *obj)
+{
+	/*
+	 * Note mm list lookup is protected by
+	 * kref_get_unless_zero().
+	 */
+	if (IS_ENABLED(CONFIG_LOCKDEP)) {
+		u32 ref = kref_read(&obj->base.refcount);
+
+		if (ref > 0 && (ref > 1 ||
+		     !list_empty_careful(&obj->mm.link) ||
+		     !list_empty_careful(&obj->mm.region_link)))
+		lockdep_assert_held(&obj->mm.lock);
+	}
+}
+
 static inline int __i915_gem_object_lock(struct drm_i915_gem_object *obj,
 					 struct i915_gem_ww_ctx *ww,
 					 bool intr)
@@ -160,6 +179,19 @@ static inline void i915_gem_object_unlock(struct drm_i915_gem_object *obj)
 	dma_resv_unlock(obj->base.resv);
 }
 
+/*
+ * Trylock that always succeeds because object isn't published yet.
+ * Helps mimic create locked functionality in TTM
+ */
+static inline void i915_gem_object_lock_isolated(struct drm_i915_gem_object *obj)
+{
+	bool locked;
+
+	assert_object_held_shared(obj);
+	locked = dma_resv_trylock(obj->base.resv);
+	GEM_BUG_ON(!locked);
+}
+
 struct dma_fence *
 i915_gem_object_lock_fence(struct drm_i915_gem_object *obj);
 void i915_gem_object_unlock_fence(struct drm_i915_gem_object *obj,
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 4dd24ccf9caf..82c0d4704113 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -20,7 +20,7 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 	struct list_head *list;
 	int i;
 
-	lockdep_assert_held(&obj->mm.lock);
+	assert_object_held_shared(obj);
 
 	if (i915_gem_object_is_volatile(obj))
 		obj->mm.madv = I915_MADV_DONTNEED;
@@ -66,6 +66,7 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 	if (i915_gem_object_is_shrinkable(obj)) {
 		unsigned long flags;
 
+		lockdep_assert_held(&obj->mm.lock);
 		spin_lock_irqsave(&i915->mm.obj_lock, flags);
 
 		i915->mm.shrink_count++;
@@ -97,6 +98,8 @@ int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 	int err;
 
+	assert_object_held_shared(obj);
+
 	if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
 		drm_dbg(&i915->drm,
 			"Attempting to obtain a purgeable object\n");
@@ -124,6 +127,8 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	if (err)
 		return err;
 
+	assert_object_held_shared(obj);
+
 	if (unlikely(!i915_gem_object_has_pages(obj))) {
 		GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 
@@ -151,7 +156,7 @@ void i915_gem_object_truncate(struct drm_i915_gem_object *obj)
 /* Try to discard unwanted pages */
 void i915_gem_object_writeback(struct drm_i915_gem_object *obj)
 {
-	lockdep_assert_held(&obj->mm.lock);
+	assert_object_held_shared(obj);
 	GEM_BUG_ON(i915_gem_object_has_pages(obj));
 
 	if (obj->ops->writeback)
@@ -183,6 +188,8 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 	struct intel_memory_region *mem = obj->mm.region;
 	struct sg_table *pages;
 
+	assert_object_held_shared(obj);
+
 	pages = fetch_and_zero(&obj->mm.pages);
 	if (IS_ERR_OR_NULL(pages))
 		return pages;
@@ -216,6 +223,9 @@ int __i915_gem_object_put_pages_locked(struct drm_i915_gem_object *obj)
 	if (i915_gem_object_has_pinned_pages(obj))
 		return -EBUSY;
 
+	/* May be called by shrinker from within get_pages() (on another bo) */
+	assert_object_held_shared(obj);
+
 	i915_gem_object_release_mmap_offset(obj);
 
 	/*
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 9a9242b5a99f..eb17560dc14d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -593,15 +593,19 @@ __i915_gem_object_create_stolen(struct intel_memory_region *mem,
 	cache_level = HAS_LLC(mem->i915) ? I915_CACHE_LLC : I915_CACHE_NONE;
 	i915_gem_object_set_cache_coherency(obj, cache_level);
 
+	i915_gem_object_lock_isolated(obj);
+
 	err = i915_gem_object_pin_pages(obj);
 	if (err)
 		goto cleanup;
 
 	i915_gem_object_init_memory_region(obj, mem);
+	i915_gem_object_unlock(obj);
 
 	return obj;
 
 cleanup:
+	i915_gem_object_unlock(obj);
 	i915_gem_object_free(obj);
 err:
 	return ERR_PTR(err);
-- 
2.28.0