drm/i915: Add i915_vma_unbind_unlocked, and take obj lock for i915_vma_unbind, v2.

We want to remove more members of i915_vma, which requires the locking to
be held more often.

Start requiring gem object lock for i915_vma_unbind, as it's one of the
callers that may unpin pages.

Some special care is needed when evicting, because the last reference to
the object may be held by the VMA, so after __i915_vma_unbind, vma may be
garbage, and we need to cache vma->obj before unlocking.

Changes since v1:
- Make trylock failing a WARN. (Matt)
- Remove double i915_vma_wait_for_bind() (Matt)
- Move atomic_set to right before mutex_unlock(), to make it more clear
  they belong together. (Matt)

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220114132320.109030-5-maarten.lankhorst@linux.intel.com

1 files changed, 25 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 9aa651d919f2..2a24986861e3 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1622,8 +1622,16 @@ void i915_vma_parked(struct intel_gt *gt)
 		struct drm_i915_gem_object *obj = vma->obj;
 		struct i915_address_space *vm = vma->vm;
 
-		INIT_LIST_HEAD(&vma->closed_link);
-		__i915_vma_put(vma);
+		if (i915_gem_object_trylock(obj, NULL)) {
+			INIT_LIST_HEAD(&vma->closed_link);
+			__i915_vma_put(vma);
+			i915_gem_object_unlock(obj);
+		} else {
+			/* back you go.. */
+			spin_lock_irq(&gt->closed_lock);
+			list_add(&vma->closed_link, &gt->closed_vma);
+			spin_unlock_irq(&gt->closed_lock);
+		}
 
 		i915_gem_object_put(obj);
 		i915_vm_close(vm);
@@ -1742,6 +1750,7 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
 	struct dma_fence *unbind_fence;
 
 	GEM_BUG_ON(i915_vma_is_pinned(vma));
+	assert_object_held_shared(vma->obj);
 
 	if (i915_vma_is_map_and_fenceable(vma)) {
 		/* Force a pagefault for domain tracking on next user access */
@@ -1808,6 +1817,7 @@ int __i915_vma_unbind(struct i915_vma *vma)
 	int ret;
 
 	lockdep_assert_held(&vma->vm->mutex);
+	assert_object_held_shared(vma->obj);
 
 	if (!drm_mm_node_allocated(&vma->node))
 		return 0;
@@ -1874,6 +1884,8 @@ int i915_vma_unbind(struct i915_vma *vma)
 	intel_wakeref_t wakeref = 0;
 	int err;
 
+	assert_object_held_shared(vma->obj);
+
 	/* Optimistic wait before taking the mutex */
 	err = i915_vma_sync(vma);
 	if (err)
@@ -1966,6 +1978,17 @@ out_rpm:
 	return err;
 }
 
+int i915_vma_unbind_unlocked(struct i915_vma *vma)
+{
+	int err;
+
+	i915_gem_object_lock(vma->obj, NULL);
+	err = i915_vma_unbind(vma);
+	i915_gem_object_unlock(vma->obj);
+
+	return err;
+}
+
 struct i915_vma *i915_vma_make_unshrinkable(struct i915_vma *vma)
 {
 	i915_gem_object_make_unshrinkable(vma->obj);