tid. magic
1    0      Worker 1 first  job in while loop
1    1      Worker 1 first  job in do_work 
1    0      Worker 1 second job in while loop
1    1      Worker 1 second job in do_work 
1   -1      Worker 1 after exiting while loop
2    0      Worker 2 first  job in while loop
2    1      Worker 2 first  job in do_work 
2    0      Worker 2 second job in while loop
2    1      Worker 2 second job in do_work 
2   -1      Worker 2 after exiting while loop