On Thu, Jan 08, 2015 at 01:05:41PM +0200, Haggai Eran wrote:
> On 06/01/2015 00:44, j.glisse@xxxxxxxxx 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.
Yes comment is out of date, i wanted to simplify fence before readding
it once needed (by device memory migration).
>
> > +
> > + /* 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?
Not right now but the page migration to device memory use it. But i
can remove it now.
I can respin to make comment match code but i would like to know where
i stand on everythings else.
Cheers,
Jérôme
>
> > +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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