class Barrier:
def __init__(self, n):
self.N_THREADS = n
self.count = 0
self.mutex = Semaphore(1)
self.turnstile = Semaphore(0)
self.turnstile2 = Semaphore(0)
def phase1(self):
self.mutex.wait()
self.count += 1
if self.count == self.N_THREADS:
for j in range(self.N_THREADS):
self.turnstile.signal()
self.mutex.signal()
self.turnstile.wait()
def phase2(self):
self.mutex.wait()
self.count -= 1
if self.count == 0:
for j in range(self.N_THREADS):
self.turnstile2.signal()
self.mutex.signal()
self.turnstile2.wait()
def wait(self):
self.phase1()
self.phase2()
class LightswitchObj:
def __init__(self):
self.count = 0
self.mutex = Semaphore(1)
def lock(self, semaphore):
self.mutex.wait()
self.count += 1
if self.count == 1:
semaphore.wait()
self.mutex.signal()
def unlock(self, semaphore):
self.mutex.wait()
self.count -= 1
if self.count == 0:
semaphore.signal()
self.mutex.signal()