On Thu, Aug 10, 2017 at 4:00 AM, Chris Wilson <ch...@chris-wilson.co.uk>
wrote:
> Quoting Jason Ekstrand (2017-08-10 00:53:00)
> > On Wed, Aug 9, 2017 at 3:41 PM, Chris Wilson <ch...@chris-wilson.co.uk>
> wrote:
> > However, this installs the proxy into syncobj->fence with the result
> > that any concurrent wait also become a WAIT_FOR_SUBMIT. The behaviour
> > of drm_syncobj is then quite inconsistent, sometimes it will wait
> for a
> > future fence, sometimes it will report an error.
> >
> >
> > Yeah, that's not good. I thought about a variety of solutions to try and
> > re-use more core dma_fence code. Ultimately I chose the current one
> because it
> > takes a snapshot of the syncobjs and then, from that point forward, it's
> > consistent with its snapshot. Nothing I was able to come up with based
> on core
> > dma_fence wait routines does that.
>
> So if we choose to keep the proxy local to the fence-array and not replace
> syncobj->fence, we can still reduce this to a plain dma-fence-array +
> wait.
>
> Pertinent details:
>
> +static void syncobj_notify(struct drm_syncobj *syncobj, struct dma_fence
> *fence)
> +{
> + struct drm_syncobj_cb *cb, *cn;
> + unsigned long flags;
> +
> + /* This is just an opencoded waitqueue; FIXME! */
> + spin_lock_irqsave(&syncobj->lock, flags);
> + list_for_each_entry_safe(cb, cn, &syncobj->cb_list, link)
> + cb->func(cb, fence);
> + INIT_LIST_HEAD(&syncobj->cb_list);
> + spin_unlock_irqrestore(&syncobj->lock, flags);
> +}
> +
> /**
> * drm_syncobj_replace_fence - replace fence in a sync object.
> * @syncobj: Sync object to replace fence in
> @@ -89,7 +109,10 @@ void drm_syncobj_replace_fence(struct drm_syncobj
> *syncobj,
>
> if (fence)
> dma_fence_get(fence);
> +
> old_fence = xchg(&syncobj->fence, fence);
> + if (!old_fence && fence)
> + syncobj_notify(syncobj, fence);
>
> dma_fence_put(old_fence);
> }
> @@ -124,6 +147,9 @@ void drm_syncobj_free(struct kref *kref)
> struct drm_syncobj *syncobj = container_of(kref,
> struct drm_syncobj,
> refcount);
> +
> + syncobj_notify(syncobj, NULL);
> +
> dma_fence_put(syncobj->fence);
> kfree(syncobj);
> }
> @@ -140,6 +166,8 @@ static int drm_syncobj_create(struct drm_file
> *file_private,
> return -ENOMEM;
>
> kref_init(&syncobj->refcount);
> + spin_lock_init(&syncobj->lock);
> + INIT_LIST_HEAD(&syncobj->cb_list);
>
> idr_preload(GFP_KERNEL);
> spin_lock(&file_private->syncobj_table_lock);
>
> struct future_fence {
> + struct drm_syncobj_cb base;
> + struct dma_fence **slot;
> +};
> +
> +static void future_fence_cb(struct drm_syncobj_cb *cb, struct dma_fence
> *fence)
> +{
> + struct future_fence *ff = container_of(cb, typeof(*ff), base);
> +
> + if (fence)
> + dma_fence_replace_proxy(ff->slot, fence);
>
Where does this come from? I can't find it on dri-devel and "proxy"
doesn't show up anywhere in the dam-buf sources. What does it do?
> + else
> + dma_fence_signal(*ff->slot);
> +
> + kfree(ff);
> +}
> +
> +int
> +drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
> + struct drm_file *file_private)
> +{
> + struct drm_syncobj_wait *args = data;
> + struct dma_fence_array *array;
> + struct dma_fence **fences;
> + unsigned int count, i;
> + long timeout;
> + u32 *handles;
> + int ret;
> +
> + BUILD_BUG_ON(sizeof(*fences) < sizeof(*handles));
> +
> + if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
> + return -ENODEV;
> +
> + if (args->flags & ~(DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL |
> + DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT))
> + return -EINVAL;
> +
> + count = args->count_handles;
> + if (!count)
> + return -EINVAL;
> +
> + /* Get the handles from userspace */
> + fences = kmalloc_array(count,
> + sizeof(struct dma_fence *),
> + __GFP_NOWARN | GFP_KERNEL);
> + if (!fences)
> + return -ENOMEM;
> +
> + handles = (void *)fences + count * (sizeof(*fences) -
> sizeof(*handles));
> + if (copy_from_user(handles,
> + u64_to_user_ptr(args->handles),
> + sizeof(u32) * count)) {
> + ret = -EFAULT;
> + goto err;
> + }
> +
> + for (i = 0; i < count; i++) {
> + struct drm_syncobj *s;
> +
> + ret = -ENOENT;
> + s = drm_syncobj_find(file_private, handles[i]);
> + if (s) {
> + ret = 0;
> + spin_lock_irq(&s->lock);
> + if (s->fence) {
> + fences[i] = dma_fence_get(s->fence);
> + } else if (args->flags &
> DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT) {
> + struct future_fence *cb;
> +
> + cb = kmalloc(sizeof(*cb), GFP_KERNEL);
> + fences[i] = dma_fence_create_proxy();
> + if (cb && fences[i]) {
> + cb->slot = &fences[i];
> + cb->base.func = future_fence_cb;
> + list_add(&cb->base.link,
> &s->cb_list);
> + } else {
> + kfree(cb);
> + dma_fence_put(fences[i]);
> + ret = -ENOMEM;
> + }
> + } else {
> + ret = -EINVAL;
> + }
> + spin_unlock_irq(&s->lock);
> + }
> + if (ret) {
> + count = i;
> + goto err_fences;
> + }
> + }
> +
> + array = dma_fence_array_create(count, fences, 0, 0,
> + !(args->flags &
> DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL));
> + if (!array) {
> + ret = -ENOMEM;
> + goto err_fences;
> + }
> +
> + timeout = drm_timeout_abs_to_jiffies(args->timeout_nsec);
> + timeout = dma_fence_wait_timeout(&array->base, true, timeout);
> + args->first_signaled = array->first_signaled;
> + dma_fence_put(&array->base);
> +
> + return timeout < 0 ? timeout : timeout == 0 ? -ETIME : 0; /* Gah.
> */
> +
> +err_fences:
> + for (i = 0; i < count; i++)
> + dma_fence_put(fences[i]);
> +err:
> + kfree(fences);
> + return ret;
> +}
>
>
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