LQ1 - Operating Systems - Processes

process

a program in execution

false

true or false: process execution must progress in parallel fashion. No sequential execution of instructions of a single process

• program code/text section

• current activity

• stack

• data section

• heap

parts of a process

heap

it contains memory dynamically allocated during run time

stack

contains temporary data, such as function parameters, return addresses, local variables

process control block (PCB) / task control block

information associated with each process

• process state

• program counter

• CPU registers

• CPU scheduling information

• memory-management information

• accounting information

• i/o status information

enumerate the parts of a process control block

process scheduling

Selects among available processes for next execution on CPU core

ready queue

set of all processes residing in main memory, ready and waiting to execute

wait queues

set of processes waiting for an event

context switch

occurs when the CPU switches from one process to another

true

true or false: When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process via a context switch

parent, children

____ process create ____ processes, which, in turn create other processes, forming a tree of processes

process identifier (PID)

Process are identified and manage via a ___ ___

fork()

a UNIX system call to create a new process

exec()

a UNIX system call used after a fork() to replace the process’ memory space with a new program

service

Android background processes use ___ to perform task. This can keep running even if background process is suspended.

wait()

a UNIX system call used to wait for the child to terminate

exit()

Process executes last statement and then asks the operating system to delete it using the ___ system call.

abort()

Parent may terminate the execution of children processes using the ___ system call.

• child has exceeded allocated resources

• task assigned to child is no longer required

• the parent is exiting, and the operating systems does not allow a child to continue if its parent terminates

what are the reasons for parents to terminate the execution of children processes?

cascading termination

All children, grandchildren, etc., are terminated.

zombie

If no parent waiting (did not invoke wait()) process is a ___

orphan

If parent terminated without invoking wait(), process is an

browser process

A type of process found in a browser that manages user interface, disk and network I/O

renderer process

A type of process found in a browser that renders web pages, deals with HTML, Javascript. A new renderer created for each website opened

sandbox

restricts disk and network I/O, and minimizes the effect of security exploits

plug-in process

A type of process found in a browser that runs for each type of plug-in

cooperating process

a type of process that can affect or be affected by other processes, including sharing data

interprocess communication (IPC)

Cooperating processes need___ ___

• shared memory

• message passing

What are the two models of IPC?

producer, consumer

___ process produces information that is consumed by a ___ process

unbounded-buffer

places no practical limit on the size of the buffer:

• producer never waits

• consumer waits if there is no buffer to consume

bounded-buffer

assumes that there is a fixed buffer size

• producer must wait if all buffers are full

• consumer waits if there is no buffer to consume

IPC - shared memory

An area of memory shared among the processes that wish to communicate

IPC - message passing

Processes communicate with each other without resorting to shared variables

communication link

If processes P and Q wish to communicate, they need to establish a ___ ___ between them

direct communication

an implementation of a communication link wherein processes must name each other explicitly

indirect communication

an implementation of a communication link wherein messages are directed and received from mailboxes

blocking is considered synchronous, whereas non-blocking is considered asynchronous

What is the difference between blocking and non-blocking in message passing

rendezvous

If both send and receive are blocking, we have a ____

buffering

queue of messages attached to the link

zero capacity

an implementation of buffering wherein no messages are queued on a link. Sender must wait for receiver (rendezvous)

bounded capacity

an implementation of buffering wherein the length of n messages is finite. Sender must wait if link is full.

unbounded capacity

an implementation of buffering wherein the length of n messages is infinite. Sender never waits.

pipes

acts as a conduit that allows two processes to communicate

ordinary pipes

a type of pipe that cannot be accessed from outside the process that created it. Typically, a parent process creates a pipe and uses it to communicate with a child process it created.

named pipes

a type of pipe that can be accessed without a parent-child relationship

ordinary pipes (or anonymous pipes)

a unidirectional pipe where they allow communication in standard producer-consumer style

named pipes

a bidirectional pipe where several processes can use it for communication.

socket

an endpoint for communication, represented as a concatenation of IP addresses and port.

port

a number included at start of message packet to differentiate network services on a host

loopback

a special IP address to refer to system on which process is running

sockets

communication consists between a pair of ____

remote procedure calls (RPC)

abstracts procedure calls between processes on network systems

stubs

client-side proxy for the actual procedure on the server

marshalls

in the context of RPCs, the client-side stub locates the server and ____ the parameters

Microsoft Interface Definition Language (MIDL)

On Windows, stub code compile from specification written in

External Data Representation (XDL)

RPC data representation is handled via ___ ___ ___ format to account for different architectures

rendezvous/matchmaker

OS typically provides a ______ service to connect client and server

the program counter and other registers

the status of the current activity of a process is represented by?

1. ready

2. running

3. waiting

4. terminated

what are the four general states of a process?

process control block (PCB)

the kernel data structure that represents a process in an operating system

sockets

allow two processes on different machines to communicate over a network.

remote procedure calls (RPC)

They abstract the concept of function calls in such a way that a function can be invoked on another process that may reside on a separate computer.