Re: [PATCH 8/9] drm/syncobj: add timeline signal ioctl for syncobj v3

[Lionel Landwerlin <lionel.g.landwerlin-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On 15/03/2019 12:09, Chunming Zhou wrote:
> v2: individually allocate chain array, since chain node is free independently.
> v3: all existing points must be already signaled before cpu perform signal operation,
>      so add check condition for that.
>
> Signed-off-by: Chunming Zhou <david1.zhou@amd.com>
> ---
>   drivers/gpu/drm/drm_internal.h |   2 +
>   drivers/gpu/drm/drm_ioctl.c    |   2 +
>   drivers/gpu/drm/drm_syncobj.c  | 103 +++++++++++++++++++++++++++++++++
>   include/uapi/drm/drm.h         |   1 +
>   4 files changed, 108 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
> index dd11ae5f1eef..d9a483a5fce0 100644
> --- a/drivers/gpu/drm/drm_internal.h
> +++ b/drivers/gpu/drm/drm_internal.h
> @@ -190,6 +190,8 @@ int drm_syncobj_reset_ioctl(struct drm_device *dev, void *data,
>   			    struct drm_file *file_private);
>   int drm_syncobj_signal_ioctl(struct drm_device *dev, void *data,
>   			     struct drm_file *file_private);
> +int drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
> +				      struct drm_file *file_private);
>   int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
>   			    struct drm_file *file_private);
>   
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 92b3b7b2fd81..d337f161909c 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -696,6 +696,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
>   		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_SIGNAL, drm_syncobj_signal_ioctl,
>   		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
> +	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL, drm_syncobj_timeline_signal_ioctl,
> +		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_QUERY, drm_syncobj_query_ioctl,
>   		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF(DRM_IOCTL_CRTC_GET_SEQUENCE, drm_crtc_get_sequence_ioctl, DRM_UNLOCKED),
> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> index 306c7b7e2770..eaeb038f97d7 100644
> --- a/drivers/gpu/drm/drm_syncobj.c
> +++ b/drivers/gpu/drm/drm_syncobj.c
> @@ -1183,6 +1183,109 @@ drm_syncobj_signal_ioctl(struct drm_device *dev, void *data,
>   	return ret;
>   }
>   
> +int
> +drm_syncobj_timeline_signal_ioctl(struct drm_device *dev, void *data,
> +				  struct drm_file *file_private)
> +{
> +	struct drm_syncobj_timeline_array *args = data;
> +	struct drm_syncobj **syncobjs;
> +	struct dma_fence_chain **chains;
> +	uint64_t *points;
> +	uint32_t i, j, timeline_count = 0;
> +	int ret;
> +
> +	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
> +		return -EOPNOTSUPP;
> +
> +	if (args->pad != 0)
> +		return -EINVAL;
> +
> +	if (args->count_handles == 0)
> +		return -EINVAL;
> +
> +	ret = drm_syncobj_array_find(file_private,
> +				     u64_to_user_ptr(args->handles),
> +				     args->count_handles,
> +				     &syncobjs);
> +	if (ret < 0)
> +		return ret;
> +
> +	for (i = 0; i < args->count_handles; i++) {
> +		struct dma_fence_chain *chain;
> +                struct dma_fence *fence;
> +
> +                fence = drm_syncobj_fence_get(syncobjs[i]);
> +                chain = to_dma_fence_chain(fence);
> +                if (chain) {
> +                        struct dma_fence *iter;
> +
> +                        dma_fence_chain_for_each(iter, fence) {
> +                                if (!iter)
> +                                        break;
> +				if (!dma_fence_is_signaled(iter)) {
> +					dma_fence_put(iter);
> +					DRM_ERROR("Client must guarantee all existing timeline points signaled before performing host signal operation!");
> +					ret = -EPERM;
> +					goto out;


Sorry if I'm failing to remember whether we discussed this before.


Signaling a point from the host should be fine even if the previous 
points in the timeline are not signaled.

After all this can happen on the device side as well (out of order 
signaling).


I thought the thing we didn't want is out of order submission.

Just checking the last chain node seqno against the host signal point 
should be enough.


What about simply returning -EPERM, we can warn the application from 
userspace?


> +				}
> +                        }
> +                }
> +        }
> +
> +	points = kmalloc_array(args->count_handles, sizeof(*points),
> +			       GFP_KERNEL);
> +	if (!points) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +	if (!u64_to_user_ptr(args->points)) {
> +		memset(points, 0, args->count_handles * sizeof(uint64_t));
> +	} else if (copy_from_user(points, u64_to_user_ptr(args->points),
> +				  sizeof(uint64_t) * args->count_handles)) {
> +		ret = -EFAULT;
> +		goto err_points;
> +	}
> +
> +
> +	for (i = 0; i < args->count_handles; i++) {
> +		if (points[i])
> +			timeline_count++;
> +	}
> +	chains = kmalloc_array(timeline_count, sizeof(void *), GFP_KERNEL);
> +	if (!chains) {
> +		ret = -ENOMEM;
> +		goto err_points;
> +	}
> +	for (i = 0; i < timeline_count; i++) {
> +		chains[i] = kzalloc(sizeof(struct dma_fence_chain), GFP_KERNEL);
> +		if (!chains[i]) {
> +			for (j = 0; j < i; j++)
> +				kfree(chains[j]);
> +			ret = -ENOMEM;
> +			goto err_chains;
> +		}
> +	}
> +
> +	for (i = 0, j = 0; i < args->count_handles; i++) {
> +		if (points[i]) {
> +			struct dma_fence *fence = dma_fence_get_stub();
> +
> +			drm_syncobj_add_point(syncobjs[i], chains[j++],


Isn't this breaking with j++ ?, it should be part of the for() loop 
expression : for (i = 0, j = 0; i < arrags->count_handles; i++, j++)


Otherwise j will not increment at the same pace as i.


> +					      fence, points[i]);
> +			dma_fence_put(fence);
> +		} else
> +			drm_syncobj_assign_null_handle(syncobjs[i]);
> +	}
> +err_chains:
> +	kfree(chains);
> +err_points:
> +	kfree(points);
> +out:
> +	drm_syncobj_array_free(syncobjs, args->count_handles);
> +
> +	return ret;
> +}
> +
>   int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
>   			    struct drm_file *file_private)
>   {
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index 4c1e2e6579fa..fe00b74268eb 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -943,6 +943,7 @@ extern "C" {
>   #define DRM_IOCTL_SYNCOBJ_TIMELINE_WAIT	DRM_IOWR(0xCA, struct drm_syncobj_timeline_wait)
>   #define DRM_IOCTL_SYNCOBJ_QUERY		DRM_IOWR(0xCB, struct drm_syncobj_timeline_array)
>   #define DRM_IOCTL_SYNCOBJ_TRANSFER	DRM_IOWR(0xCC, struct drm_syncobj_transfer)
> +#define DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL	DRM_IOWR(0xCD, struct drm_syncobj_timeline_array)
>   
>   /**
>    * Device specific ioctls should only be in their respective headers


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