OS Puzzle: Can it happen?

Consider two different threads are running the same piece of code below. When it will print the following ?

1. x is 7
2. x is 8
3. x is 9
4. x is 10

shared int x; 
x = 10; 
while (1) 
{ 
 x = x - 1; 
 x = x + 1; 
 if (x != 10) 
  printf(“x is %d”,x) 
}