Name
test_and_change_bit — 
     Change a bit and return its old value
 
Synopsis
| int test_and_change_bit ( | long nr, | 
|  | volatile unsigned long * addr ); | 
 
Arguments
- nr
- 
     Bit to change
     
- addr
- 
     Address to count from
     
Description
   This operation is atomic and cannot be reordered.
   It also implies a memory barrier.