On Fri, 2026-07-03 at 18:31 +0200, Natalie Vock wrote:
> From: Christian König <[email protected]>
>
> This should no longer be necessary, TTM doesn't lock the BO without a
> reference any more.
>
> Only compile tested!
>
> Signed-off-by: Christian König <[email protected]>
> Signed-off-by: Natalie Vock <[email protected]>
> ---
> drivers/gpu/drm/xe/xe_bo.c | 32 +++++---------------------------
> 1 file changed, 5 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 5843f850339c7..34eae56716076 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -1642,31 +1642,6 @@ static unsigned long xe_ttm_io_mem_pfn(struct
> ttm_buffer_object *ttm_bo,
>
> static void __xe_bo_vunmap(struct xe_bo *bo);
>
> -/*
> - * TODO: Move this function to TTM so we don't rely on how TTM does
> its
> - * locking, thereby abusing TTM internals.
> - */
> -static bool xe_ttm_bo_lock_in_destructor(struct ttm_buffer_object
> *ttm_bo)
> -{
> - struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
> - bool locked;
> -
> - xe_assert(xe, !kref_read(&ttm_bo->base.refcount));
> -
> - /*
> - * We can typically only race with TTM trylocking under the
> - * lru_lock, which will immediately be unlocked again since
> - * the ttm_bo refcount is zero at this point. So trylocking
> *should*
> - * always succeed here, as long as we hold the lru lock.
> - */
> - spin_lock(&ttm_bo->bdev->lru_lock);
> - locked = dma_resv_trylock(&ttm_bo->base._resv);
> - spin_unlock(&ttm_bo->bdev->lru_lock);
We could just remove the spinlocks, update the comment and keep the
asserts. Also the new code below locks .resv rather than ._resv, which
is incorrect for imported dma-bufs.
Thanks,
Thomas
> - xe_assert(xe, locked);
> -
> - return locked;
> -}
> -
> static void xe_ttm_bo_release_notify(struct ttm_buffer_object
> *ttm_bo)
> {
> struct dma_resv_iter cursor;
> @@ -1680,8 +1655,11 @@ static void xe_ttm_bo_release_notify(struct
> ttm_buffer_object *ttm_bo)
> bo = ttm_to_xe_bo(ttm_bo);
> xe_assert(xe_bo_device(bo), !(bo->created &&
> kref_read(&ttm_bo->base.refcount)));
>
> - if (!xe_ttm_bo_lock_in_destructor(ttm_bo))
> - return;
> + /*
> + * This should never fail since there are no other
> references to the BO
> + * any more.
> + */
> + WARN_ON(!dma_resv_trylock(ttm_bo->base.resv));
>
> /*
> * Scrub the preempt fences if any. The unbind fence is
> already
