Task: Multithreaded

Enter the labs/lab-06/tasks/multithreaded/ folder, run make skels, and go through the practice items below in the support/ directory.

Use the Makefile to compile multithread.c, run it and follow the instructions.

The aim of this task is to familiarize you with the pthreads library. In order to use it, you have to add #include <pthread.h> in multithreaded.c and -lpthread in the compiler options.

The executable creates 5 threads besides the main thread, puts each of them to sleep for 5 seconds, then waits for all of them to finish. Give it a run and notice that the total waiting time is around 5 seconds since you started the last thread. That is the whole point - they each run in parallel.
Make each thread print its ID once it is done sleeping.

Create a new function sleep_wrapper2() identical to sleep_wrapper() to organize your work. So far, the data argument is unused (mind the __unused attribute), so that is your starting point. You cannot change sleep_wrapper2() definition, since pthreads_create() expects a pointer to a function that receives a void * argument. What you can and should do is to pass a pointer to a int as argument, and then cast data to int * inside sleep_wrapper2().

Note: Do not simply pass &i as argument to the function. This will make all threads to use the same integer as their ID.

Note: Do not use global variables.

If you get stuck you can google pthread example and you will probably stumble upon this.
On top of printing its ID upon completion, make each thread sleep for a different amount of time.

Create a new function sleep_wrapper3() identical to sleep_wrapper() to organize your work. The idea is to repeat what you did on the previous exercise and use the right argument for sleep_wrapper3(). Keep in mind that you cannot change its definition. Bonus points if you do not use the thread’s ID as the sleeping amount.