mutex_t lock; // declare a lock cond_t cv; // declare a condition variable A condition variable (CV) is a queue of waiting threads. A single lock is associated with each CV (see below for usage) Two operations for a CV: cond_wait(cond_t *cv, mutex_t *lock) Assumes the lock is held when cond_wait() is called Puts caller to sleep + releases the lock (atomically) When awoken, reacquires lock before returning cond_signal(cond_t *cv) Wake a single waiting thread (if >= 1 thread is waiting) If there is no waiting, return w/o doing anything Using the above functions, please answer the following two questions: 4.8.1. Implementing Join with CV: void thread_exit() { done = 1; cond_signal(&c); } void thread_join() { mutex_lock (&m); if (done == 0) // a // b mutex_unlock (&m); // w // x cond_wait (&c, &m); // y // Z } How do you fix the above implementation using a lock (*m) and CV (*c)? (hint: insert function calls in the code)

mutex_t lock; // declare a lock cond_t cv; // declare a condition variable A condition variable (CV) is a queue of waiting threads. A single lock is associated with each CV (see below for usage) Two operations for a CV: cond_wait(cond_t cv, mutex_t lock) Assumes the lock is held when cond_wait() is called Puts caller to sleep + releases the lock (atomically) When awoken, reacquires lock before returning cond_signal(cond_t cv) Wake a single waiting thread (if >= 1 thread is waiting) If there is no waiting, return w/o doing anything Using the above functions, please answer the following two questions: 4.8.1. Implementing Join with CV: void thread_exit() { done = 1; cond_signal(&c); } void thread_join() { mutex_lock (&m); if (done == 0) // a // b mutex_unlock (&m); // w // x cond_wait (&c, &m); // y // Z } How do you fix the above implementation using a lock (m) and CV (*c)? (hint: insert function calls in the code)

Programming Logic & Design Comprehensive

9th Edition

ISBN:9781337669405

Author:FARRELL

Publisher:FARRELL

Chapter8: Advanced Data Handling Concepts

Section: Chapter Questions

Problem 20RQ

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Assignment 5.py: #Assignment 5 import Queueimport threadingimport timeimport random THREADS = 200 class addingThread (threading.Thread):def __init__(self, l):threading.Thread.__init__(self)self.threadID = 3self.name = "addingThread"self.l = lself.iteration = 0 def run(self):#delay start by a random time between 0 and 0.1 secsleep_time= random.randint(1,1000)/10000.0time.sleep(sleep_time)while self.iteration < len(self.l):#remove the comment for Question 1.3#lock.acquire()self.l[self.iteration] = self.l[self.iteration] +1#remove the comment for Question 1.3#lock.release()self.iteration= self.iteration + 1#remove the comment for Question 1.3 #lock = threading.Lock()workList = range(1,101)threads = [] # Create new threadsthread_num=0while thread_num < THREADS:thread = addingThread(workList)threads.append(thread)thread_num = thread_num +1 # Start threadsfor t in threads:t.start() # Wait for all created threads to finishfor t in threads:t.join() #print final listprint "Final list:…
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What is a race condition? Why is it undesirable when programming threads?
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If multiple threads are acquiring multiple locks, the order in which the threads attempt to acquire them makes no difference. True or False
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