Name
__atomic_add_unless — 
     add unless the number is already a given value
 
Synopsis
| int __atomic_add_unless ( | atomic_t * v, | 
|  | int a, | 
|  | int u ); | 
 
Arguments
- v
- 
     pointer of type atomic_t
     
- a
- 
     the amount to add to v...
     
- u
- 
     ...unless v is equal to u.
     
Description
   Atomically adds a to v, so long as v was not already u.
   Returns the old value of v.