[Intel-gfx] [PATCH 2/3] drm/i915/ttm: Fix lockdep warning in __i915_gem_free_object()

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

In the mman selftest, some tests make the ttm_bo_init_reserved() fail,
which may trigger a call to the i915_ttm_bo_destroy() function.
However, at this point the gem object refcount is set to 1, which
triggers a lockdep warning in __i915_gem_free_object() and a
corresponding failure in DG1 BAT, i915_selftest@live@mman.

Fix this by clearing the gem object refcount if called from that
failure path.

Fixes: f9b23c157a78 ("drm/i915: Move __i915_gem_free_object to ttm_bo_destroy")
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index b94497989995..b1f561543ff3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -900,6 +900,10 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
 
 	i915_ttm_backup_free(obj);
 
+	/* Failure during ttm_bo_init_reserved leaves the refcount set to 1. */
+	if (IS_ENABLED(CONFIG_LOCKDEP) && !obj->ttm.created)
+		refcount_set(&obj->base.refcount.refcount, 0);
+
 	/* This releases all gem object bindings to the backend. */
 	__i915_gem_free_object(obj);
 
-- 
2.31.1