[PATCH 01/10] dma-buf/fence: add fence_wait_any_timeout function

[Maarten Lankhorst]

Op 26-10-15 om 13:29 schreef Christian König:
> From: Christian König <christian.koenig at amd.com>
>
> Waiting for the first fence in an array of fences to signal.
>
> This is useful for device driver specific resource managers
> and also Vulkan needs something similar.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>  drivers/dma-buf/fence.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/fence.h   |  3 +-
>  2 files changed, 98 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/fence.c b/drivers/dma-buf/fence.c
> index 50ef8bd..218623f 100644
> --- a/drivers/dma-buf/fence.c
> +++ b/drivers/dma-buf/fence.c
> @@ -397,6 +397,102 @@ out:
>  }
>  EXPORT_SYMBOL(fence_default_wait);
>  
> +static bool
> +fence_test_signaled_any(struct fence **fences, uint32_t count)
> +{
> +	int i;
> +
> +	for (i = 0; i < count; ++i) {
> +		struct fence *fence = fences[i];
> +		if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
> +			return true;
> +	}
> +	return false;
> +}
> +
> +/**
> + * fence_wait_any_timeout - sleep until any fence gets signaled
> + * or until timeout elapses
> + * @fences:	[in]	array of fences to wait on
> + * @count:	[in]	number of fences to wait on
> + * @intr:	[in]	if true, do an interruptible wait
> + * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
> + *
> + * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
> + * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
> + * on success.
> + *
> + * Synchronous waits for the first fence in the array to be signaled. The
> + * caller needs to hold a reference to all fences in the array, otherwise a
> + * fence might be freed before return, resulting in undefined behavior.
> + */
> +signed long
> +fence_wait_any_timeout(struct fence **fences, uint32_t count,
> +		       bool intr, signed long timeout)
> +{
> +	struct default_wait_cb *cb;
> +	signed long ret = timeout;
> +	unsigned i;
> +
> +	if (WARN_ON(!fences))
> +		return -EINVAL;
This should probably have a check for count == 0 before this WARN_ON, so it doesn't wait an infinite amount of time when count == 0.
And it also needs to special case timeout == 0 even before that, so it still returns 1 in that case to be compatible with other wait functions.

> +	cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
> +	if (cb == NULL) {
> +		ret = -ENOMEM;
> +		goto err_free_cb;
> +	}
> +
> +	for (i = 0; i < count; ++i) {
> +		struct fence *fence = fences[i];
> +
> +		if (fence == NULL)
> +			continue;
Not sure that NULL fences should be handled here.. and in the amdgpu case surely if fence is null that means
you don't need to wait for any fence to be signaled?
> +
> +		if (fence->ops->wait != fence_default_wait) {
> +			ret = -EINVAL;
> +			goto fence_rm_cb;
> +		}
> +
> +		cb[i].task = current;
> +		if (fence_add_callback(fence, &cb[i].base,
> +				       fence_default_wait_cb)) {
> +			/* This fence is already signaled */
> +			goto fence_rm_cb;
> +		}
> +	}
> +
> +	while (ret > 0) {
> +		if (intr)
> +			set_current_state(TASK_INTERRUPTIBLE);
> +		else
> +			set_current_state(TASK_UNINTERRUPTIBLE);
> +
> +		if (fence_test_signaled_any(fences, count))
> +			break;
> +
> +		ret = schedule_timeout(ret);
> +
> +		if (ret > 0 && intr && signal_pending(current))
> +			ret = -ERESTARTSYS;
> +	}
> +
> +	__set_current_state(TASK_RUNNING);
> +
> +fence_rm_cb:
> +	for (i = 0; i < count; ++i) {
If i is not used elsewhere then the fence_remove_callback could be made
unconditional and the loop changed to
while (i-- > 0) {
> +		struct fence *fence = fences[i];
> +		if (fence && cb[i].base.func)
> +			fence_remove_callback(fence, &cb[i].base);
> +	}
> +
> +err_free_cb:
> +	kfree(cb);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(fence_wait_any_timeout);
> +
>  /**
>   * fence_init - Initialize a custom fence.
>   * @fence:	[in]	the fence to initialize
> diff --git a/include/linux/fence.h b/include/linux/fence.h
> index 39efee1..a4084d6 100644
> --- a/include/linux/fence.h
> +++ b/include/linux/fence.h
> @@ -305,7 +305,8 @@ static inline struct fence *fence_later(struct fence *f1, struct fence *f2)
>  }
>  
>  signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout);
> -
> +signed long fence_wait_any_timeout(struct fence **fences, uint32_t count,
> +				   bool intr, signed long timeout);
>  
>  /**
>   * fence_wait - sleep until the fence gets signaled