The `ttm_resource_manager_usage()` function currently assumes `man->bdev` is non-NULL when accessing `man->bdev->lru_lock`. However, in scenarios where the resource manager is not fully initialized (e.g., APU platforms that lack dedicated VRAM, or incomplete manager setup), `man->bdev` may remain NULL. This leads to a NULL pointer dereference when attempting to acquire the `lru_lock`, triggering kernel OOPS.
Fix this by adding an explicit safety check for `man->bdev` before accessing its members: - Use `WARN_ON_ONCE(!man->bdev)` to emit a one-time warning (a soft assertion) when `man->bdev` is NULL. This helps catch invalid usage patterns during debugging without breaking production workflows. - Return 0 immediately if `man->bdev` is NULL, as a non-initialized manager cannot have valid resource usage to report. Suggested-by: Christian König <[email protected]> Suggested-by: Lijo Lazar <[email protected]> Signed-off-by: Jesse Zhang <[email protected]> --- drivers/gpu/drm/ttm/ttm_resource.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c index e2c82ad07eb4..d93d1bef6768 100644 --- a/drivers/gpu/drm/ttm/ttm_resource.c +++ b/drivers/gpu/drm/ttm/ttm_resource.c @@ -587,6 +587,9 @@ uint64_t ttm_resource_manager_usage(struct ttm_resource_manager *man) { uint64_t usage; + if (WARN_ON_ONCE(!man->bdev)) + return 0; + spin_lock(&man->bdev->lru_lock); usage = man->usage; spin_unlock(&man->bdev->lru_lock); -- 2.49.0
