[Intel-gfx] [PATCH v2] drm/i915: Allow asynchronous waits on the i915_active barriers

[Tvrtko Ursulin]

On 06/04/2020 14:21, Chris Wilson wrote:
> Allow the caller to also wait upon the barriers stored in i915_active.
> 
> v2: Hook up i915_request_await_active(I915_ACTIVE_AWAIT_BARRIER) as well
> for completeness, and avoid the lazy GEM_BUG_ON()!
> 
> v3: Pull flush_lazy_signals() under the active-ref protection as it too
> walks the rbtree and so we must be careful that we do not free it as we
> iterate.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_active.c | 73 ++++++++++++++++++++++++++----
>   drivers/gpu/drm/i915/i915_active.h |  1 +
>   2 files changed, 64 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
> index d5e24be759f7..d960d0be5bd2 100644
> --- a/drivers/gpu/drm/i915/i915_active.c
> +++ b/drivers/gpu/drm/i915/i915_active.c
> @@ -542,35 +542,88 @@ static int __await_active(struct i915_active_fence *active,
>   	return 0;
>   }
>   
> +struct wait_barrier {
> +	struct wait_queue_entry base;
> +	struct i915_active *ref;
> +};
> +
> +static int
> +barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key)
> +{
> +	struct wait_barrier *wb = container_of(wq, typeof(*wb), base);
> +
> +	if (i915_active_is_idle(wb->ref)) {
> +		list_del(&wq->entry);
> +		i915_sw_fence_complete(wq->private);
> +		kfree(wq);
> +	}
> +
> +	return 0;
> +}
> +
> +static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence)
> +{
> +	struct wait_barrier *wb;
> +
> +	wb = kmalloc(sizeof(*wb), GFP_KERNEL);
> +	if (unlikely(!wb))
> +		return -ENOMEM;
> +
> +	GEM_BUG_ON(i915_active_is_idle(ref));
> +	if (!i915_sw_fence_await(fence)) {
> +		kfree(wb);
> +		return -EINVAL;
> +	}
> +
> +	wb->base.flags = 0;
> +	wb->base.func = barrier_wake;
> +	wb->base.private = fence;
> +	wb->ref = ref;
> +
> +	add_wait_queue(__var_waitqueue(ref), &wb->base);
> +	return 0;
> +}
> +
>   static int await_active(struct i915_active *ref,
>   			unsigned int flags,
>   			int (*fn)(void *arg, struct dma_fence *fence),
> -			void *arg)
> +			void *arg, struct i915_sw_fence *barrier)
>   {
>   	int err = 0;
>   
> +	if (!i915_active_acquire_if_busy(ref))
> +		return 0;
> +
>   	if (flags & I915_ACTIVE_AWAIT_EXCL &&
>   	    rcu_access_pointer(ref->excl.fence)) {
>   		err = __await_active(&ref->excl, fn, arg);
>   		if (err)
> -			return err;
> +			goto out;
>   	}
>   
> -	if (flags & I915_ACTIVE_AWAIT_ACTIVE &&
> -	    i915_active_acquire_if_busy(ref)) {
> +	if (flags & I915_ACTIVE_AWAIT_ACTIVE) {
>   		struct active_node *it, *n;
>   
>   		rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
>   			err = __await_active(&it->base, fn, arg);
>   			if (err)
> -				break;
> +				goto out;
>   		}
> -		i915_active_release(ref);
> +	}
> +
> +	if (flags & I915_ACTIVE_AWAIT_BARRIER) {
> +		err = flush_lazy_signals(ref);
>   		if (err)
> -			return err;
> +			goto out;
> +
> +		err = __await_barrier(ref, barrier);
> +		if (err)
> +			goto out;
>   	}
>   
> -	return 0;
> +out:
> +	i915_active_release(ref);
> +	return err;
>   }
>   
>   static int rq_await_fence(void *arg, struct dma_fence *fence)
> @@ -582,7 +635,7 @@ int i915_request_await_active(struct i915_request *rq,
>   			      struct i915_active *ref,
>   			      unsigned int flags)
>   {
> -	return await_active(ref, flags, rq_await_fence, rq);
> +	return await_active(ref, flags, rq_await_fence, rq, &rq->submit);
>   }
>   
>   static int sw_await_fence(void *arg, struct dma_fence *fence)
> @@ -595,7 +648,7 @@ int i915_sw_fence_await_active(struct i915_sw_fence *fence,
>   			       struct i915_active *ref,
>   			       unsigned int flags)
>   {
> -	return await_active(ref, flags, sw_await_fence, fence);
> +	return await_active(ref, flags, sw_await_fence, fence, fence);
>   }
>   
>   #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
> diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
> index ffafaa78c494..cf4058150966 100644
> --- a/drivers/gpu/drm/i915/i915_active.h
> +++ b/drivers/gpu/drm/i915/i915_active.h
> @@ -195,6 +195,7 @@ int i915_request_await_active(struct i915_request *rq,
>   			      unsigned int flags);
>   #define I915_ACTIVE_AWAIT_EXCL BIT(0)
>   #define I915_ACTIVE_AWAIT_ACTIVE BIT(1)
> +#define I915_ACTIVE_AWAIT_BARRIER BIT(2)
>   
>   int i915_active_acquire(struct i915_active *ref);
>   bool i915_active_acquire_if_busy(struct i915_active *ref);
> 

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

Regards,

Tvrtko