[Intel-gfx] [PATCH 2/2] drm/i915/fence: Separate timeout mechanism for awaiting on dma-fences

[Tvrtko Ursulin]

On 15/01/2018 09:06, Chris Wilson wrote:
> As the timeout mechanism has grown more and more complicated, using
> multiple deferred tasks and more than doubling the size of our struct,
> split the two implementations to streamline the simpler no-timeout
> callback variant.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_sw_fence.c | 61 +++++++++++++++++++++++-------------
>   1 file changed, 40 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
> index 13021326d777..1de5173e53a2 100644
> --- a/drivers/gpu/drm/i915/i915_sw_fence.c
> +++ b/drivers/gpu/drm/i915/i915_sw_fence.c
> @@ -365,18 +365,31 @@ int i915_sw_fence_await_sw_fence_gfp(struct i915_sw_fence *fence,
>   struct i915_sw_dma_fence_cb {
>   	struct dma_fence_cb base;
>   	struct i915_sw_fence *fence;
> +};
> +
> +struct i915_sw_dma_fence_cb_timer {
> +	struct i915_sw_dma_fence_cb base;
>   	struct dma_fence *dma;
>   	struct timer_list timer;
>   	struct irq_work work;
>   	struct rcu_head rcu;
>   };
>   
> +static void dma_i915_sw_fence_wake(struct dma_fence *dma,
> +				   struct dma_fence_cb *data)
> +{
> +	struct i915_sw_dma_fence_cb *cb = container_of(data, typeof(*cb), base);
> +
> +	i915_sw_fence_complete(cb->fence);
> +	kfree(cb);
> +}
> +
>   static void timer_i915_sw_fence_wake(struct timer_list *t)
>   {
> -	struct i915_sw_dma_fence_cb *cb = from_timer(cb, t, timer);
> +	struct i915_sw_dma_fence_cb_timer *cb = from_timer(cb, t, timer);
>   	struct i915_sw_fence *fence;
>   
> -	fence = xchg(&cb->fence, NULL);
> +	fence = xchg(&cb->base.fence, NULL);
>   	if (!fence)
>   		return;
>   
> @@ -388,27 +401,24 @@ static void timer_i915_sw_fence_wake(struct timer_list *t)
>   	i915_sw_fence_complete(fence);
>   }
>   
> -static void dma_i915_sw_fence_wake(struct dma_fence *dma,
> -				   struct dma_fence_cb *data)
> +static void dma_i915_sw_fence_wake_timer(struct dma_fence *dma,
> +					 struct dma_fence_cb *data)
>   {
> -	struct i915_sw_dma_fence_cb *cb = container_of(data, typeof(*cb), base);
> +	struct i915_sw_dma_fence_cb_timer *cb =
> +		container_of(data, typeof(*cb), base.base);
>   	struct i915_sw_fence *fence;
>   
> -	fence = xchg(&cb->fence, NULL);
> +	fence = xchg(&cb->base.fence, NULL);
>   	if (fence)
>   		i915_sw_fence_complete(fence);
>   
> -	if (cb->dma) {
> -		irq_work_queue(&cb->work);
> -		return;
> -	}
> -
> -	kfree(cb);
> +	irq_work_queue(&cb->work);
>   }
>   
>   static void irq_i915_sw_fence_work(struct irq_work *wrk)
>   {
> -	struct i915_sw_dma_fence_cb *cb = container_of(wrk, typeof(*cb), work);
> +	struct i915_sw_dma_fence_cb_timer *cb =
> +		container_of(wrk, typeof(*cb), work);
>   
>   	del_timer_sync(&cb->timer);
>   	dma_fence_put(cb->dma);
> @@ -422,6 +432,7 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
>   				  gfp_t gfp)
>   {
>   	struct i915_sw_dma_fence_cb *cb;
> +	dma_fence_func_t func;
>   	int ret;
>   
>   	debug_fence_assert(fence);
> @@ -430,7 +441,10 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
>   	if (dma_fence_is_signaled(dma))
>   		return 0;
>   
> -	cb = kmalloc(sizeof(*cb), gfp);
> +	cb = kmalloc(timeout ?
> +		     sizeof(struct i915_sw_dma_fence_cb_timer) :
> +		     sizeof(struct i915_sw_dma_fence_cb),
> +		     gfp);
>   	if (!cb) {
>   		if (!gfpflags_allow_blocking(gfp))
>   			return -ENOMEM;
> @@ -441,21 +455,26 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
>   	cb->fence = fence;
>   	i915_sw_fence_await(fence);
>   
> -	cb->dma = NULL;
> +	func = dma_i915_sw_fence_wake;
>   	if (timeout) {
> -		cb->dma = dma_fence_get(dma);
> -		init_irq_work(&cb->work, irq_i915_sw_fence_work);
> +		struct i915_sw_dma_fence_cb_timer *timer =
> +			container_of(cb, typeof(*timer), base);
>   
> -		timer_setup(&cb->timer,
> +		timer->dma = dma_fence_get(dma);
> +		init_irq_work(&timer->work, irq_i915_sw_fence_work);
> +
> +		timer_setup(&timer->timer,
>   			    timer_i915_sw_fence_wake, TIMER_IRQSAFE);
> -		mod_timer(&cb->timer, round_jiffies_up(jiffies + timeout));
> +		mod_timer(&timer->timer, round_jiffies_up(jiffies + timeout));
> +
> +		func = dma_i915_sw_fence_wake_timer;
>   	}
>   
> -	ret = dma_fence_add_callback(dma, &cb->base, dma_i915_sw_fence_wake);
> +	ret = dma_fence_add_callback(dma, &cb->base, func);
>   	if (ret == 0) {
>   		ret = 1;
>   	} else {
> -		dma_i915_sw_fence_wake(dma, &cb->base);
> +		func(dma, &cb->base);
>   		if (ret == -ENOENT) /* fence already signaled */
>   			ret = 0;
>   	}
> 

If it compiles, and works, assuming we have tests cases which exercise 
both paths, then it is obviously fine.

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

Regards,

Tvrtko