From fb56376caf27f59948f2b356126baab25829bffe Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 26 Jul 2022 16:48:44 +0200
Subject: drm/i915/gem: Remove shared locking on freeing objects
Git-commit: 2826d447fbd60e6a05e53d5f918bceb8c04e315c
Patch-mainline: v6.0-rc2
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225 jsc#PED-2849
Alt-commit: 7dd5c56531eb03696acdb17774721de5ef481c0b

The obj->base.resv may be shared across many objects, some of which may
still be live and locked, preventing objects from being freed
indefintely. We could individualise the lock during the free, or rely on
a freed object having no contention and being able to immediately free
the pages it owns.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/6469
Fixes: be7612fd6665 ("drm/i915: Require object lock when freeing pages during destruction")
Fixes: 6cb12fbda1c2 ("drm/i915: Use trylock instead of blocking lock for __i915_gem_free_objects.")
Cc: <stable@vger.kernel.org> # v5.17+
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Nirmoy Das <nirmoy.das@intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220726144844.18429-1-nirmoy.das@intel.com
(cherry picked from commit 7dd5c56531eb03696acdb17774721de5ef481c0b)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.c | 16 ++++------------
 drivers/gpu/drm/i915/i915_drv.h            |  4 ++--
 2 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index ccec4055fde3..389e9f157ca5 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -268,7 +268,7 @@ static void __i915_gem_object_free_mmaps(struct drm_i915_gem_object *obj)
  */
 void __i915_gem_object_pages_fini(struct drm_i915_gem_object *obj)
 {
-	assert_object_held(obj);
+	assert_object_held_shared(obj);
 
 	if (!list_empty(&obj->vma.list)) {
 		struct i915_vma *vma;
@@ -331,15 +331,7 @@ static void __i915_gem_free_objects(struct drm_i915_private *i915,
 			continue;
 		}
 
-		if (!i915_gem_object_trylock(obj, NULL)) {
-			/* busy, toss it back to the pile */
-			if (llist_add(&obj->freed, &i915->mm.free_list))
-				queue_delayed_work(i915->wq, &i915->mm.free_work, msecs_to_jiffies(10));
-			continue;
-		}
-
 		__i915_gem_object_pages_fini(obj);
-		i915_gem_object_unlock(obj);
 		__i915_gem_free_object(obj);
 
 		/* But keep the pointer alive for RCU-protected lookups */
@@ -359,7 +351,7 @@ void i915_gem_flush_free_objects(struct drm_i915_private *i915)
 static void __i915_gem_free_work(struct work_struct *work)
 {
 	struct drm_i915_private *i915 =
-		container_of(work, struct drm_i915_private, mm.free_work.work);
+		container_of(work, struct drm_i915_private, mm.free_work);
 
 	i915_gem_flush_free_objects(i915);
 }
@@ -391,7 +383,7 @@ static void i915_gem_free_object(struct drm_gem_object *gem_obj)
 	 */
 
 	if (llist_add(&obj->freed, &i915->mm.free_list))
-		queue_delayed_work(i915->wq, &i915->mm.free_work, 0);
+		queue_work(i915->wq, &i915->mm.free_work);
 }
 
 void __i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
@@ -745,7 +737,7 @@ bool i915_gem_object_needs_ccs_pages(struct drm_i915_gem_object *obj)
 
 void i915_gem_init__objects(struct drm_i915_private *i915)
 {
-	INIT_DELAYED_WORK(&i915->mm.free_work, __i915_gem_free_work);
+	INIT_WORK(&i915->mm.free_work, __i915_gem_free_work);
 }
 
 void i915_objects_module_exit(void)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d25647be25d1..086bbe8945d6 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -247,7 +247,7 @@ struct i915_gem_mm {
 	 * List of objects which are pending destruction.
 	 */
 	struct llist_head free_list;
-	struct delayed_work free_work;
+	struct work_struct free_work;
 	/**
 	 * Count of objects pending destructions. Used to skip needlessly
 	 * waiting on an RCU barrier if no objects are waiting to be freed.
@@ -1378,7 +1378,7 @@ static inline void i915_gem_drain_freed_objects(struct drm_i915_private *i915)
 	 * armed the work again.
 	 */
 	while (atomic_read(&i915->mm.free_count)) {
-		flush_delayed_work(&i915->mm.free_work);
+		flush_work(&i915->mm.free_work);
 		flush_delayed_work(&i915->bdev.wq);
 		rcu_barrier();
 	}
-- 
2.38.1