Re: [Intel-gfx] [PATCH 16/37] drm/i915: Always defer fenced work to the worker

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 05/08/2020 13:22, Chris Wilson wrote:
> Currently, if an error is raised we always call the cleanup locally
> [and skip the main work callback]. However, some future users may need
> to take a mutex to cleanup and so we cannot immediately execute the
> cleanup as we may still be in interrupt context. For example, if we have
> committed sensitive changes [like evicting from the ppGTT layout] that
> are visible but gated behind the fence, we need to ensure those changes
> are completed even after an error. [This does suggest the split between
> the work/release callback is artificial and we may be able to simplify
> the worker api by only requiring a single callback.]
> 
> With the execute-immediate flag, for most cases this should result in
> immediate cleanup of an error.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/i915_sw_fence_work.c | 26 +++++++++++------------
>   1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_sw_fence_work.c b/drivers/gpu/drm/i915/i915_sw_fence_work.c
> index a3a81bb8f2c3..e094fd0a4202 100644
> --- a/drivers/gpu/drm/i915/i915_sw_fence_work.c
> +++ b/drivers/gpu/drm/i915/i915_sw_fence_work.c
> @@ -16,11 +16,14 @@ static void fence_complete(struct dma_fence_work *f)
>   static void fence_work(struct work_struct *work)
>   {
>   	struct dma_fence_work *f = container_of(work, typeof(*f), work);
> -	int err;
>   
> -	err = f->ops->work(f);
> -	if (err)
> -		dma_fence_set_error(&f->dma, err);
> +	if (!f->dma.error) {
> +		int err;
> +
> +		err = f->ops->work(f);
> +		if (err)
> +			dma_fence_set_error(&f->dma, err);
> +	}
>   
>   	fence_complete(f);
>   	dma_fence_put(&f->dma);
> @@ -36,15 +39,10 @@ fence_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
>   		if (fence->error)
>   			dma_fence_set_error(&f->dma, fence->error);
>   
> -		if (!f->dma.error) {
> -			dma_fence_get(&f->dma);
> -			if (test_bit(DMA_FENCE_WORK_IMM, &f->dma.flags))
> -				fence_work(&f->work);
> -			else
> -				queue_work(system_unbound_wq, &f->work);
> -		} else {
> -			fence_complete(f);
> -		}
> +		if (test_bit(DMA_FENCE_WORK_IMM, &f->dma.flags))
> +			fence_work(&f->work);
> +		else
> +			queue_work(system_unbound_wq, &f->work);
>   		break;
>   
>   	case FENCE_FREE:
> @@ -91,6 +89,8 @@ void dma_fence_work_init(struct dma_fence_work *f,
>   	dma_fence_init(&f->dma, &fence_ops, &f->lock, 0, 0);
>   	i915_sw_fence_init(&f->chain, fence_notify);
>   	INIT_WORK(&f->work, fence_work);
> +
> +	dma_fence_get(&f->dma); /* once for the chain; once for the work */
>   }
>   
>   int dma_fence_work_chain(struct dma_fence_work *f, struct dma_fence *signal)
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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