P2L4

Question 1

UL Thread Data Structure

Answer 1

thread ID
UL registers
thread stack

Question 2

PCB (for threaded process)

Answer 2

Virtual address mapping
Stack
Registers

Question 3

setjmp and longjmp

Answer 3

useful for switching ULT contexts

Question 4

Hard and Light Process State

Answer 4

Portions of PCB where hard does not change for individual threads and light is thread specific

Question 5

hard process state

Answer 5

does not change from thread to thread (virtual address mappings)

Question 6

light process state

Answer 6

specific to each thread (signal mask, sys call args)

Question 7

Rationale for multiple PCB data structures

Answer 7

Scalability
overheads
performance
flexibility

Question 8

Sun KLT Data Structures

Answer 8

Process

Lightweight Process

Question 9

binding

Answer 9

associating ULT to a specific KLT

Question 10

pinning

Answer 10

associating KLT with specific CPU

Question 11

Adaptive Mutex

Answer 11

if critical section is short, spin (dont’ block)

for long critical sections default blocking behavior

Question 12

death row

Answer 12

threads periodically destroyed by a reaper thread if not reused (performance gains)

Question 13

interrupt

Answer 13

events generated externally by components other than the CPU
determined based on the physical platform
appear asynchronously

Question 14

signal

Answer 14

events triggered by CPU and software running on it
determined based on the OS
synchronous or asynchronous

Question 15

Interrupt handler table

Answer 15

Interrupts are defined by hardware

how they are handled is OS specific

Question 16

Signal handler table

Answer 16

signal is OS defined

how it is handled is process specific

Question 17

Default handler actions

Answer 17

terminate, ignore, terminate & core dump, stop or continue

Question 18

Interrupt masks are per

Answer 18

CPU

Question 19

Signal masks are per

Answer 19

execution context

Question 20

Types of Signals

Answer 20

One shot

Real time signals

Question 21

One-shot signal

Answer 21

n signals pending == 1 signal pending

Question 22

Real-time signal

Answer 22

if n signals raised, handler is called n times

Question 23

Interrupt as thread

Answer 23

if handler doesn’t lock, execute on interrupted thread’s stack
if handler locks, turn into real thread

Question 24

Interrupts top half and bottom

Answer 24

top half -> fast, non-blocking

bottom -> arbitrary complexity

Question 25

directed signal

Answer 25

signal generated by user level library to kernel level thread currently executing on another CPU

Question 26

Linux main execution abstraction

Answer 26

task

Question 27

Linux task identifer

Answer 27

pid

Question 28

Task Data Structure

Answer 28

pid, tgid, state, memory (mm), files, tasks, on_cpu, cpus_allowed

Question 29

fork in mt

Answer 29

only creates a single-threaded process

Question 30

fork in linux

Answer 30

utilizes clone under the hood

Question 31

Linux Current Threads

Answer 31

Native POSIX Threads Library (NPTL)

1:1 model

Question 32

Linux Old Threads Model

Answer 32

Linux Threads

M-M model

Question 33

MSI

Answer 33

Message Signal Interrupt

Question 34

Interrupt masks are

Answer 34

per CPU

Question 35

Signal masks are

Answer 35

per execution context

Question 36

Interrupts on multicore system

Answer 36

can be directed to a single core