IOS - synchronization project

(IOS = operating systems class at BUT FIT)

Task description (Post office)

There are 3 types of processes in the system: (0) main process, (1) postal clerk, and (2) customer. Each customer goes to the post office with one of the three types of requests: letter services, parcel services, money services. Each request is uniquely identified by a number (letters:1, parcels:2, money services:3). On arrival, they are queued according to the desired service. Each clerk serves all the queues (picking random queues each time). If there are currently no customers waiting, the clerk takes a short break. After the post office closes, clerks finish serving all customers in the queue and go home when all queues are empty. Any customers arriving after the post office closes, go home.

Detailed task specification

Each process performs its actions and simultaneously writes information about the actions to a file named proj2.out. The action output information includes the sequence number A of the action being executed (see Example output). Actions are numbered from one.

Startup:

$ ./proj2 NZ NU TZ TU F

• NZ: number of customers
• NU: number of clerks
• TZ: maximum time in milliseconds a customer waits after being created before entering the 0 <= TZ <= 10 000
• TU: The maximum length of a clerk's pause in milliseconds. 0 <= TU <= 100
• F: Maximum time in milliseconds after which the mail is closed to new arrivals. 0 <= F <= 10 000

Main process

• Ceates NZ customer processes and NU clerk processes immediately after start
• Waits a random time in the interval <F/2,F> by calling usleep
• Prints: "A: closing"
• Then waits for closure of all processes that the application creates. Once these processes are are terminated, the main process is terminated with exit code 0.

Process Customer

• Each customer is uniquely identified by idZ, 0 < idZ <= NZ
• Prints "A: Z idZ: started" after start
• Then waits a random time in the interval <0,TZ>
• If the post office is closed
  • Prints "A: Z idZ: going home"
  • Process ends
• If the post office is open, randomly selects an X (number activity from the interval <1,3>)
  • Print: "A: Z idZ: entering office for a service X"
  • Queues X and waits to be called by a clerk
  • Print: "Z idZ: called by office worker"
  • Then waits a random time in the interval <0,10> (synchronization with clerk to complete the request is not required).
  • Prints "A: Z idZ: going home"
  • Process ends

Process clerk

• Each clerk is uniquely identified by the number idU, 0 < idU <= NU
• prints: "A: U idU: started" when started [start of the cycle].
• The clerk goes to serve the customer from queue X (a random non-empty queue)
  • Prints "A: U idU: serving a service of type X"
  • Then waits a random time in the interval <0,10>
  • Print "A: U idU: service finished"
  • Continues to [start of the cycle]
• If there is no customer waiting in any queue and post office is open
  • Print !A: U idU: taking break"
  • Then waits a random time in the interval <0,TU>
  • Print "A: U idU: break finished"
  • Continues to [start of the cycle]
• If there is no customer waiting in any queue and the post office is closed
  • Print "A: U idU: going home"
  • Process ends

Example output

Example output file proj2.out for the ommand

$ ./proj2 3 2 100 100 100

1: U 1: started
2: Z 3: started
3: Z 1: started
4: Z 1: entering office for a service 2
5: U 2: started
6: Z 2: started
7: Z 3: entering office for a service 1
8: Z 1: called by office worker
9: U 1: serving a service of type 2
10: U 1: service finished
11: Z 1: going home
12: Z 3: called by office worker
13: U 2: serving a service of type 1
14: U 1: taking break
15: closing
16: U 1: break finished
17: U 1: going home
18: Z 2: going home
19: U 2: service finished
20: U 2: going home
21: Z 3: going home