Re: [PATCH] dma-fence: Fix dma_fence_timeline_name() to call get_timeline_name()

[Philipp Stanner <phasta@mailbox.org>]

+Cc André

On Thu, 2026-06-25 at 22:12 +0800, Baineng Shou wrote:
> dma_fence_timeline_name() incorrectly invokes ops->get_driver_name()
> instead of ops->get_timeline_name(), so every caller receives the
> driver name where the timeline name was expected.
> 
> This is a copy-paste regression that has resurfaced twice. It was
> originally introduced by commit 62918542b7bf ("dma-fence: Fix sparse
> warnings due __rcu annotations") when adding the __rcu casts, fixed
> by commit 033559473dd3 ("dma-fence: Fix safe access wrapper to call
> timeline name method"), and then accidentally reintroduced by commit
> e58b4dea9054 ("dma-buf/dma-fence: Add dma_fence_test_signaled_flag()")
> when both wrappers were refactored to use the new helper.
> 
> Signed-off-by: Baineng Shou <shoubaineng@gmail.com>

André has caught this a few days ago already:

https://lore.kernel.org/dri-devel/20260618-linux-drm_crtc_fix-v1-1-801f29c9853d@linaro.org/


To save my honor I want to state that e58b4dea9054 did not actually *do
this* change. But merging it must have caused it somehow, since that
commit was still based on the old bug. I guess somewhere in conflict
resolution somehow tho old code must have entered.


P.

> ---
>  drivers/dma-buf/dma-fence.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index b3bfa6943a8e..5292d714419b 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -1202,7 +1202,7 @@ const char __rcu *dma_fence_timeline_name(struct dma_fence *fence)
>  	/* RCU protection is required for safe access to returned string */
>  	ops = rcu_dereference(fence->ops);
>  	if (!dma_fence_test_signaled_flag(fence))
> -		return (const char __rcu *)ops->get_driver_name(fence);
> +		return (const char __rcu *)ops->get_timeline_name(fence);
>  	else
>  		return (const char __rcu *)"signaled-timeline";
>  }