Re: [PATCH 5/6] drm/amdgpu: Don't hardcode thread name length

[Luben Tuikov <luben.tuikov@amd.com>]

On 2020-11-25 04:55, Christian König wrote:
> Am 25.11.20 um 04:17 schrieb Luben Tuikov:
>> Introduce a macro DRM_THREAD_NAME_LEN
>> and use that to define ring name size,
>> instead of hardcoding it to 16.
>>
>> Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 2 +-
>>   include/drm/gpu_scheduler.h              | 2 ++
>>   2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
>> index 7112137689db..bbd46c6dec65 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
>> @@ -230,7 +230,7 @@ struct amdgpu_ring {
>>   	unsigned		wptr_offs;
>>   	unsigned		fence_offs;
>>   	uint64_t		current_ctx;
>> -	char			name[16];
>> +	char			name[DRM_THREAD_NAME_LEN];
>>   	u32                     trail_seq;
>>   	unsigned		trail_fence_offs;
>>   	u64			trail_fence_gpu_addr;
>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>> index 61f7121e1c19..3a5686c3b5e9 100644
>> --- a/include/drm/gpu_scheduler.h
>> +++ b/include/drm/gpu_scheduler.h
>> @@ -30,6 +30,8 @@
>>   
>>   #define MAX_WAIT_SCHED_ENTITY_Q_EMPTY msecs_to_jiffies(1000)
>>   
>> +#define DRM_THREAD_NAME_LEN     TASK_COMM_LEN
>> +
> 
> The thread name is an amdgpu specific thing. I don't think we should 
> have that in the scheduler.

I need it in DRM when creating the done thread from the name
of the main scheduler thread. Since DRM creates threads,
the main scheduler thread and the done thread, it would
be good to have a preliminary limit to the name string.

> 
> And why do you use TASK_COMM_LEN here? That is completely unrelated stuff.

If you trace down into the kernel, TASK_COMM_LEN seems to be used in
snprintf() when naming a kernel thread, and its value is 16--same
as the one used in amdgpu.

So the size of the name string transitions from amdgpu to DRM to kernel
proper, where amdgpu and kernel proper set it to max 16, but DRM doesn't
give it a limit.

Sure, I can remove it from DRM, and just use a local limit
when snprintf() the name when creating a tread, possibly
using TASK_COMM_LEN. (That's in the next patch.)

Would that be better? I can do that in v2 of this patchset.

Thanks,
Luben

> 
> Regards,
> Christian.
> 
>>   struct drm_gpu_scheduler;
>>   struct drm_sched_rq;
>>   
> 

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