[PATCH 0/6] make ctx mgr global

[Christian König]

Am 24.08.2016 um 12:01 schrieb zhoucm1:
>
>
> On 2016年08月24日 17:39, Christian König wrote:
>> Am 24.08.2016 um 11:33 schrieb zhoucm1:
>>>
>>>
>>> On 2016年08月18日 16:15, Christian König wrote:
>>>> NAK to the whole approach.
>>>>
>>>> If we want to share dependencies in the form of fences between 
>>>> devices and especially processes we must use android fences and the 
>>>> sync file framework.
>>> Then if we want to share semaphore between devices and processes, we 
>>> must re-implement semaphore and move it to kernel side from libdrm, 
>>> right?
>>> then bind unused fd to semaphore object, and then export/import fd.
>>> What do you think of it?
>>
>> That is basically what sync_file does. It just doesn't call it 
>> semaphore and doesn't use the signal/wait semantic.
>>
>> Instead fences can be added to a sync_file and waited for completion 
>> before a command submission is made.
> I understand your mean, UMD don't want to touch command submission to 
> semaphore, which isn't what semaphore want to do.
> semaphore does:
> 1. create a semaphore
> 2. signal semahore----append the last fence of that ctx to semaphore 
> in lidrm
> 3. wait semaphore----add semaphore to ctx->semaphore_list in libdrm, 
> when next submission is comming, then semaphore will be dependency of it.
> 4. destroy semaphore.
> the umd totally doesn't know what semaphore does, they just know the 
> synchronization is completed after semaphore, then they can continue 
> to do cs.
>
> sync_file seems cannot provide what semaphore does. So with thinking 
> more, we seems have to move semaphore implementation to kernel, use 
> unused fd and install it to fd like sync file mechanism to share 
> semaphore between devices and  processes, right?

No, as far as I can see sync_file does exactly the same thing as 
semaphores in libdrm, they just use a fd as handle.

E.g. same concept, but different name and slightly different approaches 
of handling things (actually much saner ones, cause sync_file can't 
deadlock).

Regards,
Christian.

>
>
> Regards,
> David Zhou
>>
>> Regards,
>> Christian.
>>
>>>
>>> Regards,
>>> David Zhou
>>>>
>>>> Sharing numbers in the form of the IDR is a security nightmare we 
>>>> already ran into with the GEM flink design.
>>>>
>>>> Regards,
>>>> Christian.
>>>>
>>>> Am 18.08.2016 um 09:50 schrieb Chunming Zhou:
>>>>> If we want to share semaphore/dependency across process across 
>>>>> device, we
>>>>> must make ctx id be global, so that we can index it everywhere.
>>>>>
>>>>> Chunming Zhou (6):
>>>>>    drm/amdgpu: use global ctx mgr instead of vm specified
>>>>>    drm/amdgpu: clean up for amdgpu ctx
>>>>>    drm/amdgpu: allocate progressively higher ids for ctx until idr
>>>>>      counter wraps
>>>>>    drm/amdgpu: ctx id should be removed when ctx is freed
>>>>>    drm/amdgpu: use fence-array for ctx release
>>>>>    drm/amdgpu: dependency is already signaled if ctx has been freed
>>>>>
>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h     |  17 ++--
>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c  |   9 +-
>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 142 
>>>>> ++++++++++++++++++--------------
>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c |   3 +
>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c |   4 -
>>>>>   5 files changed, 92 insertions(+), 83 deletions(-)
>>>>>
>>>>
>>>
>>
>