Operating Systems - CS604 Power Point Slides Lecture 12

7/25/2019 Operating Systems - CS604 Power Point Slides Lecture 12

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Operating

SystemsLecture 12


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January 27, 2016 Copyright Virtual University of Paistan

Agenda for Today

!evie" of previous lectureProcess #anage#ent co##an$s%

bg, fg, ^Z, jobs, ^C, kill&hrea$ concept

Pros an$ cons of threa$s

User an$ ernel threa$s

Pthrea$s li'rary "ith e(a#ple

!ecap of lecture


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Review of Lecture 11

Use of )*)+s in a progra#a#ple co$e

Process #anage#ent inU-*./Linu(

U-*./Linu( co##an$s/calls%mknod, mkfifo, ps, top


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The fgCommand

fg [%job_id]

fgresu#es the e(ecution of a

suspen$e$ o' in the foregroun$an$ #oves a 'acgroun$ o'

into the foregroun$ *f %job_id is o#itte$ the

current o' is assu#e$


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The bgcommand

bg [ %job_id]bgresu#es the e(ecution of a

suspen$e$ o' in the'acgroun$

*f o'3i$ is o#itte$ the currento' is assu#e$ bgruns the current or specifie$

o's in the 'acgroun$


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The jobscommand

jobs

jobs$isplays status of

suspen$e$ an$ 'acgroun$processes


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Suspending a Processsen$s a &+P/UP4-5signal to the current process &heshell $isplays a #essage saying that

the o' has 'een suspen$e$ an$$isplays its pro#pt

ou can then #anipulate the state ofthis o', put it in the 'acgroun$ "iththe bgco##an$, run so#e otherco##an$s, an$ then eventually 'ringthe o' 'ac into the foregroun$ "ith

the fgco##an$


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$ find / -name foo -print 2> /dev/null^Z

[1]+ Stopped find -n!me foo -print "> de#nll

$bg

[1]+ find -n!me foo -print "> de#nll

$ jobs

[1]+ &nning find -n!me foo -print "> de#nll

$ fg

find -n!me foo -print "> de#nll

[ 'omm!nd otpt ]

$

Sample Session


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Terminating Current

Processsen$s the **-&

signal to the current process,"hich, 'y $efault, ter#inates

the process$ find / -name foo -print 1> out 2> /dev/null

^C

$


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Terminating a Process

kill [-sign!l] ()*sen$ssignal nu#'er 8signal9 to process

"ith *5 8P*59kill 1"sen$s the *&4!:

signal to the process "ith *5 12;kill ,sen$s the 8sure ill9

signal, eg, kill , ./"/


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Terminating a Process

kill ,l$isplays the signalssupporte$ 'y the syste# an$

their nu#'ers$ kill -l10 S)23( "0 S))45 0 S)63)5 /0 S))77

80 S)5&9( :0 S)9;&5 0 S)=5 ?0 S)@(=

0 S)A)77 1.0 S);3S 110 S)S=B 1"0 S)SS

10 S)()(= 1/0 S)97& 180 S)5=& 1:0 S)3S&1

DDD

$


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Issues with Processes

&he foruire$ to pass

infor#ation 'et"een a parent

an$ its chil$ processes


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Thread Concept

? threa$ is a @light"eightA process"hich e(ecutes "ithin the a$$ressspace of a process

? threa$ can 'e sche$ule$ to run

on a CPU as an in$epen$ent unit

an$ ter#inate

:ultiple threa$s can run

si#ultaneously


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Thread Concept

&hrea$s have their o"n&hrea$ *5

CPU conte(t


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Thread Concept

&hrea$s shareCo$e an$ $ata

+pen files


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Single andultithreaded

Processes


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Threads are Similar to

Processes? threa$ can 'e in states si#ilar

to a process


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Threads are !ifferent

from Processes:ultiple threa$s can operate

"ithin the sa#e a$$ress space-o @auto#aticA protection

#echanis# is in place forthrea$sthey are #eant to help

each other


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Advantages of Threads

Responsiveness

:ultiDthrea$e$ servers


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!esource sharing

Process resources


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Economy&ae less ti#e to create,

sche$ule, an$ ter#inateolaris 2% threa$ creation is ;0

ti#es faster than process

creation an$ threa$ s"itching is

five ti#es faster than process

s"itching


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Performancein #ultiDprocessor

an$ #ultiDthrea$e$ architectures


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!isadvantages of

Threads!esource sharing

synchroniGation nee$e$'et"een threa$s

5ifficult to "rite an$ $e'ug#ultiDthrea$e$ progra#s


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January 27, 2016 Copyright Virtual Universit f P i t

Recap of Lecture

User an$ ernel threa$sPthrea$s

a#ple co$eU-*./Linu( co##an$s/calls%

ptEre!d_'re!te,ptEre!d_join,

ptEre!d eFit

Operating Systems - CS604 Power Point Slides Lecture 12

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