[PATCH] drm/amdgpu: add AMDGPU_IB_FLAG_GET_START_SYNCOBJ to expose scheduled fence

[Christian König]

Am 29.01.19 um 22:54 schrieb Marek Olšák:
> On Tue, Jan 29, 2019 at 3:01 AM Christian König 
> <ckoenig.leichtzumerken at gmail.com 
> <mailto:ckoenig.leichtzumerken at gmail.com>> wrote:
>
>     Am 28.01.19 um 22:52 schrieb Marek Olšák:
>     > From: Marek Olšák <marek.olsak at amd.com <mailto:marek.olsak at amd.com>>
>     >
>     > Normal syncobjs signal when an IB finishes. Start syncobjs
>     signal when
>     > an IB starts.
>
>     That approach has quite a number of problems (for example you can't
>     allocate memory at this point).
>
>
> Even if I drop this patch, can you describe all the problems with it? 
> Andrey and I would like to understand this.

> amdgpu_mn_lock(p->mn);
> ...
> r = drm_syncobj_create(&syncobj, 0,...

You can't allocate memory while holding the MN lock, so calling 
drm_syncobj_create() here is forbidden.

> r = drm_syncobj_get_handle(p->filp, syncobj,...

This can fail which would result in a syncobj which is never signaled 
nor freed.

Regards,
Christian.

>
> Thanks,
> Marek
>
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