drm/i915: Promote i915->mm.obj_lock to be irqsafe

The intent is to be able to update the mm.lists from inside an irqsoff
section (e.g. from a softirq rcu workqueue), ergo we need to make the
i915->mm.obj_lock irqsafe.

v2: can_discard_pages() ensures we are shrinkable
v3: Beware shadowing of 'flags'

Fixes: 3b4fa964 ("drm/i915: Track the purgeable objects on a separate eviction list")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110869Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190610145430.17717-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_domain.c

@@ -475,15 +475,20 @@ static void i915_gem_object_bump_inactive_ggtt(struct drm_i915_gem_object *obj)
 	}
 	mutex_unlock(&i915->ggtt.vm.mutex);
 
-	if (i915_gem_object_is_shrinkable(obj) &&
-	    obj->mm.madv == I915_MADV_WILLNEED) {
-		struct list_head *list;
-
-		spin_lock(&i915->mm.obj_lock);
-		list = obj->bind_count ?
-			&i915->mm.bound_list : &i915->mm.unbound_list;
-		list_move_tail(&obj->mm.link, list);
-		spin_unlock(&i915->mm.obj_lock);
+	if (i915_gem_object_is_shrinkable(obj)) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&i915->mm.obj_lock, flags);
+
+		if (obj->mm.madv == I915_MADV_WILLNEED) {
+			struct list_head *list;
+
+			list = obj->bind_count ?
+				&i915->mm.bound_list : &i915->mm.unbound_list;
+			list_move_tail(&obj->mm.link, list);
+		}
+
+		spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 	}
 }
 

drivers/gpu/drm/i915/gem/i915_gem_object.c

@@ -207,9 +207,11 @@ static void __i915_gem_free_objects(struct drm_i915_private *i915,
 		 */
 		if (i915_gem_object_has_pages(obj) &&
 		    i915_gem_object_is_shrinkable(obj)) {
-			spin_lock(&i915->mm.obj_lock);
+			unsigned long flags;
+
+			spin_lock_irqsave(&i915->mm.obj_lock, flags);
 			list_del_init(&obj->mm.link);
-			spin_unlock(&i915->mm.obj_lock);
+			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 		}
 
 		mutex_unlock(&i915->drm.struct_mutex);
@@ -330,9 +332,11 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
 		obj->mm.madv = I915_MADV_DONTNEED;
 
 		if (i915_gem_object_has_pages(obj)) {
-			spin_lock(&i915->mm.obj_lock);
+			unsigned long flags;
+
+			spin_lock_irqsave(&i915->mm.obj_lock, flags);
 			list_move_tail(&obj->mm.link, &i915->mm.purge_list);
-			spin_unlock(&i915->mm.obj_lock);
+			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 		}
 	}
 

drivers/gpu/drm/i915/gem/i915_gem_pages.c

@@ -57,11 +57,15 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 	GEM_BUG_ON(!HAS_PAGE_SIZES(i915, obj->mm.page_sizes.sg));
 
 	if (i915_gem_object_is_shrinkable(obj)) {
-		spin_lock(&i915->mm.obj_lock);
+		unsigned long flags;
+
+		spin_lock_irqsave(&i915->mm.obj_lock, flags);
+
 		i915->mm.shrink_count++;
 		i915->mm.shrink_memory += obj->base.size;
 		list_add(&obj->mm.link, &i915->mm.unbound_list);
-		spin_unlock(&i915->mm.obj_lock);
+
+		spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 	}
 }
 
@@ -151,11 +155,15 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 		return pages;
 
 	if (i915_gem_object_is_shrinkable(obj)) {
-		spin_lock(&i915->mm.obj_lock);
+		unsigned long flags;
+
+		spin_lock_irqsave(&i915->mm.obj_lock, flags);
+
 		list_del(&obj->mm.link);
 		i915->mm.shrink_count--;
 		i915->mm.shrink_memory -= obj->base.size;
-		spin_unlock(&i915->mm.obj_lock);
+
+		spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 	}
 
 	if (obj->mm.mapping) {

drivers/gpu/drm/i915/gem/i915_gem_shrinker.c

@@ -138,7 +138,7 @@ unsigned long
 i915_gem_shrink(struct drm_i915_private *i915,
 		unsigned long target,
 		unsigned long *nr_scanned,
-		unsigned flags)
+		unsigned int shrink)
 {
 	const struct {
 		struct list_head *list;
@@ -154,7 +154,7 @@ i915_gem_shrink(struct drm_i915_private *i915,
 	unsigned long scanned = 0;
 	bool unlock;
 
-	if (!shrinker_lock(i915, flags, &unlock))
+	if (!shrinker_lock(i915, shrink, &unlock))
 		return 0;
 
 	/*
@@ -166,12 +166,12 @@ i915_gem_shrink(struct drm_i915_private *i915,
 	 * We don't care about errors here; if we cannot wait upon the GPU,
 	 * we will free as much as we can and hope to get a second chance.
 	 */
-	if (flags & I915_SHRINK_ACTIVE)
+	if (shrink & I915_SHRINK_ACTIVE)
 		i915_gem_wait_for_idle(i915,
 				       I915_WAIT_LOCKED,
 				       MAX_SCHEDULE_TIMEOUT);
 
-	trace_i915_gem_shrink(i915, target, flags);
+	trace_i915_gem_shrink(i915, target, shrink);
 	i915_retire_requests(i915);
 
 	/*
@@ -179,10 +179,10 @@ i915_gem_shrink(struct drm_i915_private *i915,
 	 * device just to recover a little memory. If absolutely necessary,
 	 * we will force the wake during oom-notifier.
 	 */
-	if (flags & I915_SHRINK_BOUND) {
+	if (shrink & I915_SHRINK_BOUND) {
 		wakeref = intel_runtime_pm_get_if_in_use(i915);
 		if (!wakeref)
-			flags &= ~I915_SHRINK_BOUND;
+			shrink &= ~I915_SHRINK_BOUND;
 	}
 
 	/*
@@ -207,8 +207,9 @@ i915_gem_shrink(struct drm_i915_private *i915,
 	for (phase = phases; phase->list; phase++) {
 		struct list_head still_in_list;
 		struct drm_i915_gem_object *obj;
+		unsigned long flags;
 
-		if ((flags & phase->bit) == 0)
+		if ((shrink & phase->bit) == 0)
 			continue;
 
 		INIT_LIST_HEAD(&still_in_list);
@@ -220,50 +221,50 @@ i915_gem_shrink(struct drm_i915_private *i915,
 		 * to be able to shrink their pages, so they remain on
 		 * the unbound/bound list until actually freed.
 		 */
-		spin_lock(&i915->mm.obj_lock);
+		spin_lock_irqsave(&i915->mm.obj_lock, flags);
 		while (count < target &&
 		       (obj = list_first_entry_or_null(phase->list,
 						       typeof(*obj),
 						       mm.link))) {
 			list_move_tail(&obj->mm.link, &still_in_list);
 
-			if (flags & I915_SHRINK_VMAPS &&
+			if (shrink & I915_SHRINK_VMAPS &&
 			    !is_vmalloc_addr(obj->mm.mapping))
 				continue;
 
-			if (!(flags & I915_SHRINK_ACTIVE) &&
+			if (!(shrink & I915_SHRINK_ACTIVE) &&
 			    (i915_gem_object_is_active(obj) ||
 			     i915_gem_object_is_framebuffer(obj)))
 				continue;
 
-			if (!(flags & I915_SHRINK_BOUND) &&
+			if (!(shrink & I915_SHRINK_BOUND) &&
 			    READ_ONCE(obj->bind_count))
 				continue;
 
 			if (!can_release_pages(obj))
 				continue;
 
-			spin_unlock(&i915->mm.obj_lock);
+			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
 			if (unsafe_drop_pages(obj)) {
 				/* May arrive from get_pages on another bo */
 				mutex_lock_nested(&obj->mm.lock,
 						  I915_MM_SHRINKER);
 				if (!i915_gem_object_has_pages(obj)) {
-					try_to_writeback(obj, flags);
+					try_to_writeback(obj, shrink);
 					count += obj->base.size >> PAGE_SHIFT;
 				}
 				mutex_unlock(&obj->mm.lock);
 			}
 			scanned += obj->base.size >> PAGE_SHIFT;
 
-			spin_lock(&i915->mm.obj_lock);
+			spin_lock_irqsave(&i915->mm.obj_lock, flags);
 		}
 		list_splice_tail(&still_in_list, phase->list);
-		spin_unlock(&i915->mm.obj_lock);
+		spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 	}
 
-	if (flags & I915_SHRINK_BOUND)
+	if (shrink & I915_SHRINK_BOUND)
 		intel_runtime_pm_put(i915, wakeref);
 
 	i915_retire_requests(i915);
@@ -379,6 +380,7 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 	struct drm_i915_gem_object *obj;
 	unsigned long unevictable, bound, unbound, freed_pages;
 	intel_wakeref_t wakeref;
+	unsigned long flags;
 
 	freed_pages = 0;
 	with_intel_runtime_pm(i915, wakeref)
@@ -392,7 +394,7 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 	 * being pointed to by hardware.
 	 */
 	unbound = bound = unevictable = 0;
-	spin_lock(&i915->mm.obj_lock);
+	spin_lock_irqsave(&i915->mm.obj_lock, flags);
 	list_for_each_entry(obj, &i915->mm.unbound_list, mm.link) {
 		if (!can_release_pages(obj))
 			unevictable += obj->base.size >> PAGE_SHIFT;
@@ -405,7 +407,7 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 		else
 			bound += obj->base.size >> PAGE_SHIFT;
 	}
-	spin_unlock(&i915->mm.obj_lock);
+	spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
 	if (freed_pages || unbound || bound)
 		pr_info("Purging GPU memory, %lu pages freed, "

drivers/gpu/drm/i915/gem/i915_gem_stolen.c

@@ -613,6 +613,7 @@ i915_gem_object_create_stolen_for_preallocated(struct drm_i915_private *dev_priv
 	struct drm_i915_gem_object *obj;
 	struct drm_mm_node *stolen;
 	struct i915_vma *vma;
+	unsigned long flags;
 	int ret;
 
 	if (!drm_mm_initialized(&dev_priv->mm.stolen))
@@ -689,10 +690,10 @@ i915_gem_object_create_stolen_for_preallocated(struct drm_i915_private *dev_priv
 	list_move_tail(&vma->vm_link, &ggtt->vm.bound_list);
 	mutex_unlock(&ggtt->vm.mutex);
 
-	spin_lock(&dev_priv->mm.obj_lock);
+	spin_lock_irqsave(&dev_priv->mm.obj_lock, flags);
 	GEM_BUG_ON(i915_gem_object_is_shrinkable(obj));
 	obj->bind_count++;
-	spin_unlock(&dev_priv->mm.obj_lock);
+	spin_unlock_irqrestore(&dev_priv->mm.obj_lock, flags);
 
 	return obj;
 

drivers/gpu/drm/i915/i915_debugfs.c

@@ -269,6 +269,7 @@ static int i915_gem_stolen_list_info(struct seq_file *m, void *data)
 	struct drm_i915_gem_object *obj;
 	u64 total_obj_size, total_gtt_size;
 	unsigned long total, count, n;
+	unsigned long flags;
 	int ret;
 
 	total = READ_ONCE(dev_priv->mm.shrink_count);
@@ -282,7 +283,7 @@ static int i915_gem_stolen_list_info(struct seq_file *m, void *data)
 
 	total_obj_size = total_gtt_size = count = 0;
 
-	spin_lock(&dev_priv->mm.obj_lock);
+	spin_lock_irqsave(&dev_priv->mm.obj_lock, flags);
 	list_for_each_entry(obj, &dev_priv->mm.bound_list, mm.link) {
 		if (count == total)
 			break;
@@ -305,7 +306,7 @@ static int i915_gem_stolen_list_info(struct seq_file *m, void *data)
 		objects[count++] = obj;
 		total_obj_size += obj->base.size;
 	}
-	spin_unlock(&dev_priv->mm.obj_lock);
+	spin_unlock_irqrestore(&dev_priv->mm.obj_lock, flags);
 
 	sort(objects, count, sizeof(*objects), obj_rank_by_stolen, NULL);
 
@@ -457,6 +458,7 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
 	u64 size, mapped_size, purgeable_size, dpy_size, huge_size;
 	struct drm_i915_gem_object *obj;
 	unsigned int page_sizes = 0;
+	unsigned long flags;
 	char buf[80];
 	int ret;
 
@@ -469,7 +471,7 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
 	purgeable_size = purgeable_count = 0;
 	huge_size = huge_count = 0;
 
-	spin_lock(&dev_priv->mm.obj_lock);
+	spin_lock_irqsave(&dev_priv->mm.obj_lock, flags);
 	list_for_each_entry(obj, &dev_priv->mm.unbound_list, mm.link) {
 		size += obj->base.size;
 		++count;
@@ -518,7 +520,7 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
 			page_sizes |= obj->mm.page_sizes.sg;
 		}
 	}
-	spin_unlock(&dev_priv->mm.obj_lock);
+	spin_unlock_irqrestore(&dev_priv->mm.obj_lock, flags);
 
 	seq_printf(m, "%u bound objects, %llu bytes\n",
 		   count, size);

drivers/gpu/drm/i915/i915_gem.c

@@ -1138,7 +1138,10 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 		struct list_head *list;
 
 		if (i915_gem_object_is_shrinkable(obj)) {
-			spin_lock(&i915->mm.obj_lock);
+			unsigned long flags;
+
+			spin_lock_irqsave(&i915->mm.obj_lock, flags);
+
 			if (obj->mm.madv != I915_MADV_WILLNEED)
 				list = &i915->mm.purge_list;
 			else if (obj->bind_count)
@@ -1146,7 +1149,8 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 			else
 				list = &i915->mm.unbound_list;
 			list_move_tail(&obj->mm.link, list);
-			spin_unlock(&i915->mm.obj_lock);
+
+			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 		}
 	}
 

drivers/gpu/drm/i915/i915_vma.c

@@ -80,11 +80,14 @@ static void vma_print_allocator(struct i915_vma *vma, const char *reason)
 static void obj_bump_mru(struct drm_i915_gem_object *obj)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+	unsigned long flags;
+
+	spin_lock_irqsave(&i915->mm.obj_lock, flags);
 
-	spin_lock(&i915->mm.obj_lock);
 	if (obj->bind_count)
 		list_move_tail(&obj->mm.link, &i915->mm.bound_list);
-	spin_unlock(&i915->mm.obj_lock);
+
+	spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
 	obj->mm.dirty = true; /* be paranoid  */
 }
@@ -678,8 +681,9 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 
 	if (vma->obj) {
 		struct drm_i915_gem_object *obj = vma->obj;
+		unsigned long flags;
 
-		spin_lock(&dev_priv->mm.obj_lock);
+		spin_lock_irqsave(&dev_priv->mm.obj_lock, flags);
 
 		if (i915_gem_object_is_shrinkable(obj))
 			list_move_tail(&obj->mm.link, &dev_priv->mm.bound_list);
@@ -687,7 +691,7 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 		obj->bind_count++;
 		assert_bind_count(obj);
 
-		spin_unlock(&dev_priv->mm.obj_lock);
+		spin_unlock_irqrestore(&dev_priv->mm.obj_lock, flags);
 	}
 
 	return 0;
@@ -721,8 +725,9 @@ i915_vma_remove(struct i915_vma *vma)
 	 */
 	if (vma->obj) {
 		struct drm_i915_gem_object *obj = vma->obj;
+		unsigned long flags;
 
-		spin_lock(&i915->mm.obj_lock);
+		spin_lock_irqsave(&i915->mm.obj_lock, flags);
 
 		GEM_BUG_ON(obj->bind_count == 0);
 		if (--obj->bind_count == 0 &&
@@ -730,7 +735,7 @@ i915_vma_remove(struct i915_vma *vma)
 		    obj->mm.madv == I915_MADV_WILLNEED)
 			list_move_tail(&obj->mm.link, &i915->mm.unbound_list);
 
-		spin_unlock(&i915->mm.obj_lock);
+		spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
 		/*
 		 * And finally now the object is completely decoupled from this