Uyuyan berber sorunu

Bilgisayar mühendisliğinde, uyuyan berber sorunu işletim sistemleri konusunda klasik bir sorundur. Berber ve müşteriler prosesler olarak düşünülebilir.

Gerçekleme

• Aşağıdaki sözde kod berber ve müşteriler için ölümcül kilitlenme olmayan bir çözümdür ancak açlığa yol açabilir.

Semaphore Customers = 0
Semaphore Barber = 0
Semaphore accessSeats = 1  # mutex
int NumberOfFreeSeats = N  # total number of seats
 
def Barber():
  while true:                 # Run in an infinite loop.
    P(Customers)              # Try to acquire a customer - if none is available, go to sleep.
    P(accessSeats)            # I have been awakened - modify the number of available seats.
    NumberOfFreeSeats++       # One chair gets free.
    V(Barber)                 # I am ready to cut.
    V(accessSeats)            # Don't need the lock on the chairs anymore.
    # (Cut hair here.)
 
def Customer():
  while true:                 # Run in an infinite loop.
    P(accessSeats)            # Try to get access to the chairs.
    if NumberOfFreeSeats > 0: # If there are any free seats:
      NumberOfFreeSeats--     #   sit down on a chair
      V(Customers)            #   notify the barber, who's waiting until there is a customer
      V(accessSeats)          #   don't need to lock the chairs anymore
      P(Barber)               #   now it's this customer's turn, but wait if the barber is busy.
      # (Have hair cut here.)
    else:                     # otherwise, there are no free seats; tough luck --
      V(accessSeats)          #   but don't forget to release the lock on the seats!
      # (Leave without a haircut.)