Re: [PATCH 2/2] dma-fence: Simply wrap dma_fence_signal_locked with dma_fence_signal

["Koenig, Christian" <Christian.Koenig@amd.com>]

Am 16.08.19 um 17:21 schrieb Chris Wilson:
> Currently dma_fence_signal() tries to avoid the spinlock and only takes
> it if absolutely required to walk the callback list. However, to allow
> for some users to surreptitiously insert lazy signal callbacks that
> do not depend on enabling the signaling mechanism around every fence,
> we always need to notify the callbacks on signaling. As such, we will
> always need to take the spinlock and dma_fence_signal() effectively
> becomes a clone of dma_fence_signal_locked().
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>   drivers/dma-buf/dma-fence.c | 19 +++++--------------
>   1 file changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index ff0cd6eae766..f23eb9f19b4e 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -176,6 +176,7 @@ EXPORT_SYMBOL(dma_fence_signal_locked);
>   int dma_fence_signal(struct dma_fence *fence)
>   {
>   	unsigned long flags;
> +	int ret;
>   
>   	if (!fence)
>   		return -EINVAL;
> @@ -183,21 +184,11 @@ int dma_fence_signal(struct dma_fence *fence)
>   	if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
>   		return -EINVAL;

I need to take my review back. You also need to drop this 
test_and_set_bit here or your completely break drivers using this.

Regards,
Christian.

>   
> -	fence->timestamp = ktime_get();
> -	set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
> -	trace_dma_fence_signaled(fence);
> -
> -	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
> -		struct dma_fence_cb *cur, *tmp;
> +	spin_lock_irqsave(fence->lock, flags);
> +	ret = dma_fence_signal_locked(fence);
> +	spin_unlock_irqrestore(fence->lock, flags);
>   
> -		spin_lock_irqsave(fence->lock, flags);
> -		list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
> -			list_del_init(&cur->node);
> -			cur->func(fence, cur);
> -		}
> -		spin_unlock_irqrestore(fence->lock, flags);
> -	}
> -	return 0;
> +	return ret;
>   }
>   EXPORT_SYMBOL(dma_fence_signal);
>   

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