[Intel-gfx] [PATCH 14/31] drm/i915: Only signal from interrupt when requested

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Avoid calling dma_fence_signal() from inside the interrupt if we haven't
> enabled signaling on the request.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_irq.c         | 8 ++++++--
>  drivers/gpu/drm/i915/i915_request.c     | 2 +-
>  drivers/gpu/drm/i915/intel_ringbuffer.h | 5 ++---
>  3 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 6730c1a7f135..0f0e64c915a2 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -1173,7 +1173,8 @@ static void notify_ring(struct intel_engine_cs *engine)
>  		if (i915_seqno_passed(seqno, wait->seqno)) {
>  			struct i915_request *waiter = wait->request;
>  
> -			if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
> +			if (waiter &&
> +			    !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
>  				      &waiter->fence.flags) &&
>  			    intel_wait_check_request(wait, waiter))
>  				rq = i915_request_get(waiter);
> @@ -1196,8 +1197,11 @@ static void notify_ring(struct intel_engine_cs *engine)
>  	spin_unlock(&engine->breadcrumbs.irq_lock);
>  
>  	if (rq) {
> -		dma_fence_signal(&rq->fence);
> +		spin_lock(&rq->lock);
> +		dma_fence_signal_locked(&rq->fence);
>  		GEM_BUG_ON(!i915_request_completed(rq));
> +		spin_unlock(&rq->lock);
> +
>  		i915_request_put(rq);
>  	}
>  
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 696125663105..14bf0be6f994 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -1250,7 +1250,7 @@ long i915_request_wait(struct i915_request *rq,
>  	if (flags & I915_WAIT_LOCKED)
>  		add_wait_queue(errq, &reset);
>  
> -	intel_wait_init(&wait, rq);
> +	intel_wait_init(&wait);
>  
>  restart:
>  	do {
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 33602eb1c77f..4fd7c7b80fdb 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -940,11 +940,10 @@ static inline u32 intel_hws_preempt_done_address(struct intel_engine_cs *engine)
>  /* intel_breadcrumbs.c -- user interrupt bottom-half for waiters */
>  int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine);
>  
> -static inline void intel_wait_init(struct intel_wait *wait,
> -				   struct i915_request *rq)
> +static inline void intel_wait_init(struct intel_wait *wait)
>  {
>  	wait->tsk = current;
> -	wait->request = rq;
> +	wait->request = NULL;

Enabling signaling will setup the correct request for
those who might be wondering. So reduced locking and using more
lightweight variant.

Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>