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

[Christian König]

Am 26.09.2018 um 18:43 schrieb 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?

ttm_bo_get_unless_zero() is fine with me as well.

Christian.

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