Question

Give a programming example in python of a deadlock with semaphore lock. please include output screenshot.

Answer 1

# TEXT CODE STARTS HERE

# import threading module to use Semaphore
import threading

#import time to make thread sleep for specified time
import time

# create two semaphores sem1 and sem2
sem1 = threading.Semaphore()
sem2 = threading.Semaphore()

# defining method fun1() to run in thread t1
# thread t1 will try to acquire locks in order sem1 then sem2
def fun1():
   # print some message about thread1
print("Thread1 started")

while True:
       # acquire lock on sem1
sem1.acquire()

# make thread t1 to sleep for 1 sec.
time.sleep(1)

# qcquire lock on sem2
sem2.acquire()

# print string "THREAD1"
print("THREAD1")

# release lock on sem2
sem2.release()

# release lock on sem1
sem1.release()

# defining method fun1() to run in thread t2
# thread t2 will try to acquire locks in order sem2 then sem1
def fun2():
   # print some message about thread2
print("Thread2 sarted")

while True:
   # acquire lock on sem2
sem2.acquire()

# make thread t2 to sleep for 1 sec.
time.sleep(1)

# qcquire lock on sem1
sem1.acquire()

# print string "THREAD2"
print("THREAD2")

# release lock on sem1
sem1.release()

# release lock on sem2
sem2.release()

  
# create thread t1 with target method fun1
t1 = threading.Thread(target = fun1)

# start thread t1
t1.start()

# create thread t1 with target method fun1
t2 = threading.Thread(target = fun2)

# start thread t1
t2.start()

# TEXT CODE ENDS HERE

SCREENSHOTS:

code:

output ( Thread1 and Thread2 has successfully started but fall in deadlock ) :

NOTE:-