[PATCH 0/9] drm/syncobj: Add full-featured wait support (v2)

[Jason Ekstrand]

On August 13, 2017 6:19:53 AM Christian König <christian.koenig at amd.com> wrote:

> Patches #1-#4 are Acked-by: Christian König <christian.koenig at amd.com>.
>
> Patch #5: NAK, that will break radeon.
>
> On radeon we need the non-default wait or otherwise we can run into a
> situation where we never signal a fence.
>
> The general question is why do you need this?

Because i915 sets a non-default wait function so calling wait_any just 
bails with fences from i915 immediately bails with -EINVAL.  This makes it 
work even with non-default waits.

> Patch #6: Yes, please. Patch is Reviewed-by: Christian König
> <christian.koenig at amd.com>.
>
> Patch #7: Already gave my rb on the patch Chris send out earlier.
>
> Patch #8: NAK to the whole approach.
>
> IIRC we discussed a very similar thing during the initial fence bringup
> and also during the fence_array development.
>
> The problem is that you can easily build ring dependencies and so
> deadlocks with it.
>
> I would really prefer an approach which is completely contained inside
> the syncobj code base.

Are you use to the approach of internally making a proxy so long as all the 
proxy code is inside syncobj?  Is also be happy to go back to the original 
approach with v3 of the last patch.

> Regards,
> Christian.
>
> Am 12.08.2017 um 00:39 schrieb Jason Ekstrand:
>> This series does the same thing as my earlier series in that it adds a sync
>> object wait interface complete with WAIT_FOR_SUBMIT flag.  While the uapi
>> remains unchanged, the guts look a bit different.  Instead of adding a
>> callback mechanism to drm_syncobj that fired whenever replace_fence was
>> called, it's now using proxy fences.  The drm_syncobj_fence_get still
>> returns NULL whenever the sync object is in an unsubmitted state but there
>> is a new drm_syncobj_fence_proxy_get which returns either the real fence or
>> a proxy fence that will be triggered the next time replace_fence is called
>> with a non-NULL replacement.  This does make both drm_syncobj_fence_get and
>> drm_syncobj_replace_fence a tiny bit more expensive, but it lets us do it
>> all without locking.
>>
>> This series can be found as a branch here:
>>
>> https://cgit.freedesktop.org/~jekstrand/linux/log/?h=drm-syncobj-wait-submit-v4
>>
>> IGT tests for DRM_IOCTL_SYNCOBJ_WAIT and DRM_IOCTL_SYNCOBJ_RESET can be
>> found on patchwork here:
>>
>> https://patchwork.freedesktop.org/series/28666/
>>
>> Patches to the Intel Vulkan driver to implement VK_KHR_external_fence on
>> top of this kernel interface can be found here:
>>
>> https://cgit.freedesktop.org/~jekstrand/mesa/log/?h=wip/anv-external-fence
>>
>> Cc: Dave Airlie <airlied at redhat.com>
>> Cc: Chris Wilson <chris at chris-wilson.co.uk>
>> Cc: Christian König <christian.koenig at amd.com>
>>
>> Chris Wilson (2):
>>    dma-buf/dma-fence: Signal all callbacks from dma_fence_release()
>>    dma-buf/dma-fence: Add a mechanism for proxy fences
>>
>> Dave Airlie (1):
>>    drm/syncobj: add sync obj wait interface. (v8)
>>
>> Jason Ekstrand (6):
>>    drm/syncobj: Rename fence_get to find_fence
>>    drm/syncobj: Add a race-free drm_syncobj_fence_get helper
>>    i915: Add support for drm syncobjs
>>    dma-buf/dma-fence: Allow wait_any_timeout without default_wait (v2)
>>    drm/syncobj: Add a reset ioctl
>>    drm/syncobj: Allow wait for submit and signal behavior (v4)
>>
>>   drivers/dma-buf/Makefile                   |   4 +-
>>   drivers/dma-buf/dma-fence-proxy.c          | 186 +++++++++++++++++++
>>   drivers/dma-buf/dma-fence.c                |  34 ++--
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c     |   2 +-
>>   drivers/gpu/drm/drm_internal.h             |   4 +
>>   drivers/gpu/drm/drm_ioctl.c                |   4 +
>>   drivers/gpu/drm/drm_syncobj.c              | 275 +++++++++++++++++++++++++++--
>>   drivers/gpu/drm/i915/i915_drv.c            |   3 +-
>>   drivers/gpu/drm/i915/i915_gem_execbuffer.c | 146 ++++++++++++++-
>>   include/drm/drm_syncobj.h                  |  15 +-
>>   include/linux/dma-fence-proxy.h            |  25 +++
>>   include/uapi/drm/drm.h                     |  19 ++
>>   include/uapi/drm/i915_drm.h                |  30 +++-
>>   13 files changed, 710 insertions(+), 37 deletions(-)
>>   create mode 100644 drivers/dma-buf/dma-fence-proxy.c
>>   create mode 100644 include/linux/dma-fence-proxy.h
>>
>