Process Management

Question 1

Succinctly describe a process.

Answer 1

A unit of resource allocation.

Question 2

Succinctly describe a thread.

Answer 2

A unit of execution.

Question 3

What’s a major difference between a process and a thread?

Answer 3

(Many answers)
Processes are collections of one or more threads.

Processes have a PID; Threads have associated variables.

Processes have Virtual Memory dedicated to them; Threads share memory (by def’n).

Question 4

What’s the C command for getting a process ID?

Answer 4

getpid(void). Returns a pid_t.

Question 5

What’s the C command for creating a thread?

Answer 5

pthread_create(pthread_t& thread, <attr.s>, void* thread_fn, void* arg);</attr.s>

Question 6

What is a signal?

Answer 6

A special event delivered to a process (or many).

Question 7

How can I call a signal?

Answer 7

sighandler_t signal(int signum, sighandler_t handler);

Question 8

What makes signals distinct from hardware interrupts?

Answer 8

Signals are handled by the OS, and may go through many handlers. Hardware interrupts touch hardware.

Question 9

What is polling?

Answer 9

The process of actively checking for events (signals, interrupts) at regular intervals.

Question 10

What is Reentrant & Thread-Safe Code?

Answer 10

Code that allows for calling when it’s already running. Does not modify global or static variables, and only uses its own arguments and local variables.

Question 11

What is Parallelism?

Answer 11

The process of running multiple threads at the same time using dedicated hardware resources.

Question 12

What is Concurrency?

Answer 12

The process of running multiple threads at the same time using shared hardware resources.

Question 13

What’s the major difference between Parallelism and Concurrency?

Answer 13

Parallelism is guaranteed to utilize simultaneous execution; Concurrency merely imitates it.

Question 14

Why is multithreading effective?

Answer 14

Multi-core systems.

Question 15

TRUE/FALSE: Threads have their own address spaces.

Answer 15

FALSE: Threads share the same address space in order to access the heap, any global variables, etc.

Question 16

How can one enable mutual exclusion while multithreading?

Answer 16

Mutexes and condition variables.

Question 17

What are CPU Set/Jmp primitives primarily used for?

Answer 17

Exception handling.

Question 18

What does setjmp do?

Answer 18

Saves the state of the program for later use.

Question 19

What does longjmp do?

Answer 19

Jumps to an earlier saved state.

Question 20

What project did we build with setjmp and longjmp? (Project purpose, not number)

Answer 20

The scheduler.

Question 21

What is the primary mechanism to create a process in Linux?

Answer 21

pid_t fork(void);

Question 22

When running fork, what pid will the child process have?

Answer 22

0.

Question 23

TRUE/FALSE: When forking a process, the parent resources will be copied for the child process.

Answer 23

TRUE.

Question 24

What is a fork call primarily used for?

Answer 24

An execv call.

Question 25

What does a join (waitpid) operation do in relation to forking?

Answer 25

Join processes (like waitpid) wait for the child process to complete before completing.

Question 26

What are Linux Pipes?

Answer 26

Linux pipes enable communication between processes, and can chain together outputs and inputs.

Question 27

TRUE/FALSE: Memory mapping is another mechanism for inter-process communication.

Answer 27

TRUE.

Question 28

What does the Linker do?

Answer 28

Connects different process together and into a single executable. Managed by the OS. Creates .so objects.

Question 29

TRUE/FALSE: When managing more processes than cores, the scheduler divides threads and processes among the cores, letting each core concurrently run the processes assigned.

Answer 29

FALSE: The scheduler can multiplex the processes, moving threads to different cores over the duration of its running.