[PATCH -next 12/18] drm/ttm: Export ttm_bo_reference_unless_doomed()

[Thomas Hellstrom]

On 09/26/2018 06:35 PM, Christian König wrote:
> Am 26.09.2018 um 18:18 schrieb Thomas Hellstrom:
>> Export ttm_bo_reference_unless_doomed() to be used when looking up 
>> buffer
>> objects that are removed from the lookup structure in the destructor.
>>
>> Cc: Christian König <christian.koenig at amd.com>
>> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
>> Reviewed-by: Sinclair Yeh <syeh at vmware.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo_vm.c |  3 +--
>>   include/drm/ttm/ttm_bo_api.h    | 18 ++++++++++++++++++
>>   2 files changed, 19 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c 
>> b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>> index 6fe91c1b692d..ec4b09366213 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>> @@ -409,8 +409,7 @@ static struct ttm_buffer_object 
>> *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
>>       node = drm_vma_offset_lookup_locked(&bdev->vma_manager, offset, 
>> pages);
>>       if (likely(node)) {
>>           bo = container_of(node, struct ttm_buffer_object, vma_node);
>> -        if (!kref_get_unless_zero(&bo->kref))
>> -            bo = NULL;
>> +        bo = ttm_bo_reference_unless_doomed(bo);
>>       }
>>         drm_vma_offset_unlock_lookup(&bdev->vma_manager);
>> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
>> index 8c19470785e2..b6bf6b086576 100644
>> --- a/include/drm/ttm/ttm_bo_api.h
>> +++ b/include/drm/ttm/ttm_bo_api.h
>> @@ -312,6 +312,24 @@ ttm_bo_reference(struct ttm_buffer_object *bo)
>>       return bo;
>>   }
>>   +/**
>> + * ttm_bo_reference_unless_doomed - reference a struct 
>> ttm_buffer_object unless
>> + * its refcount has already reached zero.
>> + * @bo: The buffer object.
>> + *
>> + * Used to reference a TTM buffer object in lookups where the object 
>> is removed
>> + * from the lookup structure during the destructor and for RCU lookups.
>> + *
>> + * Returns: @bo if the referencing was successful, NULL otherwise.
>> + */
>> +static inline __must_check struct ttm_buffer_object *
>> +ttm_bo_reference_unless_doomed(struct ttm_buffer_object *bo)
>
> Please name that ttm_bo_get_rcu(), we are in the process of renaming 
> ttm_bo_reference into ttm_bo_get as well.

Could we call it ttm_bo_get_unless_doomed() or ttm_bo_get_unless_zero() 
to be even more consistent. (It's not restricted to rcu as the VM usage 
shows). Also "doomed" is more relevant for objects, "zero" is more 
relevant for the refcount itself?

/Thomas



>
> Christian.
>
>> +{
>> +    if (!kref_get_unless_zero(&bo->kref))
>> +        return NULL;
>> +    return bo;
>> +}
>> +
>>   /**
>>    * ttm_bo_wait - wait for buffer idle.
>>    *
>