On 06/01/2015 00:44, j.gli...@gmail.com wrote:
> + /* fence_wait() - to wait on device driver fence.
> + *
> + * @fence: The device driver fence struct.
> + * Returns: 0 on success,-EIO on error, -EAGAIN to wait again.
> + *
> + * Called when hmm want to wait for all operations associated with a
> + * fence to complete (including device cache flush if the event mandate
> + * it).
> + *
> + * Device driver must free fence and associated resources if it returns
> + * something else thant -EAGAIN. On -EAGAIN the fence must not be free
> + * as hmm will call back again.
> + *
> + * Return error if scheduled operation failed or if need to wait again.
> + * -EIO Some input/output error with the device.
> + * -EAGAIN The fence not yet signaled, hmm reschedule waiting thread.
> + *
> + * All other return value trigger warning and are transformed to -EIO.
> + */
> + int (*fence_wait)(struct hmm_fence *fence);
According to the comment, the device frees the fence struct when the
fence_wait callback returns zero or -EIO, but the code below calls
fence_unref after fence_wait on the same fence.
> +
> + /* fence_ref() - take a reference fence structure.
> + *
> + * @fence: Fence structure hmm is referencing.
> + */
> + void (*fence_ref)(struct hmm_fence *fence);
I don't see fence_ref being called anywhere in the patchset. Is it
actually needed?
> +static void hmm_device_fence_wait(struct hmm_device *device,
> + struct hmm_fence *fence)
> +{
> + struct hmm_mirror *mirror;
> + int r;
> +
> + if (fence == NULL)
> + return;
> +
> + list_del_init(&fence->list);
> + do {
> + r = device->ops->fence_wait(fence);
> + if (r == -EAGAIN)
> + io_schedule();
> + } while (r == -EAGAIN);
> +
> + mirror = fence->mirror;
> + device->ops->fence_unref(fence);
> + if (r)
> + hmm_mirror_release(mirror);
> +}
> +
Regards,
Haggai
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