[RFC 01/17] dma-fence: add might_sleep annotation to _wait()

[Chris Wilson]

Quoting Daniel Vetter (2020-05-12 09:59:28)
> But only for non-zero timeout, to avoid false positives.
> 
> One question here is whether the might_sleep should be unconditional,
> or only for real timeouts. I'm not sure, so went with the more
> defensive option. But in the interest of locking down the cross-driver
> dma_fence rules we might want to be more aggressive.

You can argue for enforcing might_sleep() as internal queries should be
using dma_fence_is_signaled() and not dma_fence_wait_timeout(0).

> Cc: linux-media at vger.kernel.org
> Cc: linaro-mm-sig at lists.linaro.org
> Cc: linux-rdma at vger.kernel.org
> Cc: amd-gfx at lists.freedesktop.org
> Cc: intel-gfx at lists.freedesktop.org
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Christian König <christian.koenig at amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/dma-buf/dma-fence.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 052a41e2451c..6802125349fb 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -208,6 +208,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
>         if (WARN_ON(timeout < 0))
>                 return -EINVAL;
>  
> +       if (timeout > 0)
> +               might_sleep();

might_sleep_if(timeout > 0);
-Chris