multithreading - Why does this sleeping barber solution not cause a deadlock? -



multithreading - Why does this sleeping barber solution not cause a deadlock? -

considering sleeping barber problem, have next solution have 2 status variables customer_available , barber_available in monitor:

get_haircut if num_free_chairs > 0 num_free_chairs := num_free_chairs - 1 customer_available.signal barber_available.wait do_haircut if num_free_chairs = n customer_available.wait barber_available.signal num_free_chairs := num_free_chairs + 1

now, assume first client goes in , calls customer_available_signal , wakes barber up; assume barber thread starts , executes finish function , starts wait on customer_available 1 time again (assume thread calling do_haircut method 1 time again , again). , context switches , client thread stucks on barber_available status causing deadlock. so, solution seemed wrong me, same in several different sources.

is because methods in monitor atomic , client guaranteed phone call customer_available.signal , barber_available.wait sequentially before barber thread continues execution?

multithreading synchronization

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