[Intel-gfx] [PATCH 07/42] drm/i915: Allow i915_sw_fence_await_sw_fence() to allocate

[Tvrtko Ursulin]

On 07/10/2016 10:46, Chris Wilson wrote:
> In forthcoming patches, we want to be able to dynamically allocate the
> wait_queue_t used whilst awaiting. This is more convenient if we extend
> the i915_sw_fence_await_sw_fence() to perform the allocation for us if
> we pass in a gfp mask as an alternative than a preallocated struct.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_sw_fence.c | 40 ++++++++++++++++++++++++++++++++----
>   drivers/gpu/drm/i915/i915_sw_fence.h |  8 ++++++++
>   2 files changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
> index 1e5cbc585ca2..dfb59dced0ce 100644
> --- a/drivers/gpu/drm/i915/i915_sw_fence.c
> +++ b/drivers/gpu/drm/i915/i915_sw_fence.c
> @@ -13,6 +13,8 @@
>   
>   #include "i915_sw_fence.h"
>   
> +#define I915_SW_FENCE_FLAG_ALLOC BIT(0)
> +

You collide with WQ_FLAG_EXCLUSIVE here, so I assume i915 will have 
complete control of the wq in question?

>   static DEFINE_SPINLOCK(i915_sw_fence_lock);
>   
>   static int __i915_sw_fence_notify(struct i915_sw_fence *fence,
> @@ -135,6 +137,8 @@ static int i915_sw_fence_wake(wait_queue_t *wq, unsigned mode, int flags, void *
>   	list_del(&wq->task_list);
>   	__i915_sw_fence_complete(wq->private, key);
>   	i915_sw_fence_put(wq->private);
> +	if (wq->flags & I915_SW_FENCE_FLAG_ALLOC)
> +		kfree(wq);
>   	return 0;
>   }
>   
> @@ -192,9 +196,9 @@ static bool i915_sw_fence_check_if_after(struct i915_sw_fence *fence,
>   	return err;
>   }
>   
> -int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
> -				 struct i915_sw_fence *signaler,
> -				 wait_queue_t *wq)
> +static int __i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
> +					  struct i915_sw_fence *signaler,
> +					  wait_queue_t *wq, gfp_t gfp)
>   {
>   	unsigned long flags;
>   	int pending;
> @@ -206,8 +210,22 @@ int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
>   	if (unlikely(i915_sw_fence_check_if_after(fence, signaler)))
>   		return -EINVAL;
>   
> +	pending = 0;
> +	if (!wq) {
> +		wq = kmalloc(sizeof(*wq), gfp);
> +		if (!wq) {
> +			if (!gfpflags_allow_blocking(gfp))
> +				return -ENOMEM;
> +
> +			i915_sw_fence_wait(signaler);

This looks like a strange API, unless I am missing something - it 
normally sets things up for waiting, unless the allocation fails when it 
actually does the wait?

> +			return 0;
> +		}
> +
> +		pending |= I915_SW_FENCE_FLAG_ALLOC;

Why is this stored in pending? Just because it is around as re-used?

> +	}
> +
>   	INIT_LIST_HEAD(&wq->task_list);
> -	wq->flags = 0;
> +	wq->flags = pending;
>   	wq->func = i915_sw_fence_wake;
>   	wq->private = i915_sw_fence_get(fence);
>   
> @@ -226,6 +244,20 @@ int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
>   	return pending;
>   }
>   
> +int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
> +				 struct i915_sw_fence *signaler,
> +				 wait_queue_t *wq)
> +{
> +	return __i915_sw_fence_await_sw_fence(fence, signaler, wq, 0);
> +}
> +
> +int i915_sw_fence_await_sw_fence_gfp(struct i915_sw_fence *fence,
> +				     struct i915_sw_fence *signaler,
> +				     gfp_t gfp)
> +{
> +	return __i915_sw_fence_await_sw_fence(fence, signaler, NULL, gfp);
> +}
> +
>   struct dma_fence_cb {
>   	struct fence_cb base;
>   	struct i915_sw_fence *fence;
> diff --git a/drivers/gpu/drm/i915/i915_sw_fence.h b/drivers/gpu/drm/i915/i915_sw_fence.h
> index 373141602ca4..5861c69f24d4 100644
> --- a/drivers/gpu/drm/i915/i915_sw_fence.h
> +++ b/drivers/gpu/drm/i915/i915_sw_fence.h
> @@ -46,6 +46,9 @@ void i915_sw_fence_commit(struct i915_sw_fence *fence);
>   int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
>   				 struct i915_sw_fence *after,
>   				 wait_queue_t *wq);
> +int i915_sw_fence_await_sw_fence_gfp(struct i915_sw_fence *fence,
> +				     struct i915_sw_fence *after,
> +				     gfp_t gfp);
>   int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
>   				  struct fence *dma,
>   				  unsigned long timeout,
> @@ -62,4 +65,9 @@ static inline bool i915_sw_fence_done(const struct i915_sw_fence *fence)
>   	return atomic_read(&fence->pending) < 0;
>   }
>   
> +static inline void i915_sw_fence_wait(struct i915_sw_fence *fence)
> +{
> +	wait_event(fence->wait, i915_sw_fence_done(fence));
> +}
> +
>   #endif /* _I915_SW_FENCE_H_ */

Regards,

Tvrtko