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21 TOPIC: FILES CHAPT 622 TOPIC: SECURITY, CHAPT 9
REVIEW OF THE TOPICS TO BE TREATED IN DETAIL
18 TOPIC: INPUT-OUTPUT BACKGROUND HARDWARE: CHAPT 5[2]
20 TOPIC: MEMORY MANAGEMENT:PROCESSES-CONTINUOUS; PAGED CHAPT 419 TOPICS: PROCESSES , DEADLOCK CHAPT 2, 3
23 THREADS (GLOBAL MEMORY, CONTROL OS OR PROCESS) CHAPT 224 SHARED MEMORY PROCESSORS AND THEIR OPERATING SYSTEMs CHAPT 8
12 UNIX PROCESS CREATION, THE FORK13 SHELL STRUCTURES USING FORK14 A SHELL USING FORK-TRACE15 CREATING PROCESSES FORK PARENT-CHILD RELATIONS
PROCESS CREATION AND USE IN UNIX-BASIC SYSTEM CALLS
16 UNIX OPERATING SYSTEM CALLS, LIBRARY FUNCTIONS, IPC
OPERATING SYSTEM (OS:)ITS PURPOSE, INTEGRATION WITH OTHER COMPONENTS OF COMPUTER SYSTEM AND HISTORIC OUTLINE
4 BOOTSTRAPPING Incremental Development Of Compilers And OS
6 HISTORY-SOME HIGHLIGHTS
3 OPERATING SYSTEM CALLS ARE “INTERPRETED” with LIBRARY ANDKERNEL CODE
2 PURPOSE OF OPERATING SYSTEM THE SHELL SYSTEM FUNCTIONS
5 THE OPERATING SYSTEM POSITION IN THE COMPUTER LANGUAGE HIERARCHY
BASIC: OPERATING SYSTEM IS USED AND IS NEEDED TO IMPLEMENT: (PSEUDO) PARALLEL PROCESSES[TIME-SHARING, MULTI-PROGRAMMING)CHAPTERS: PROCESSES AND MEMMORY MANAGEMENT.
7 MULTIPROGRAMMING-MANY PROCESS SIMULTANEOUSLY PRESENT(EACH GIVEN EPISODES OF CONTINUOUS TIME)
8 PROCESSES, THREADS, STATES
11 PARALLEL VS PSEUDO PARALLEL -INVALID SEQUENCING OF MUTUALLYEXCLUSIVE REGIONS
9 MULTIPROGRAMMING WITH ONE CPU Single Threaded Processes10 PARALLEL VS PSEUDO PARALLEL- VALID SEQUENCING OF MUTUALLY
EXCLUSIVE REGIONS
© 2007 M.C. PAULL 1CONTENTS
17 MORE ABOUT IPC WITH PIPES
read(cmd)generateprocess
implementcmd
suicidewait
SHELL
IN
OUTdatesort
standard
cat
read(cmd)generateprocess
implementcmd
suicidewait
SHELL
INdatesort
standard
terminals
cat
OUT
OS
. . . .
I/O
FILES
PROCESSES. . .
MEMORY
TIMERS
. . . .
In fact the actual machine may be many machines, either all together in one location, or distributed. Somemay be specialized for handling one aspect of the necessary work, ex. a File Server. However, for the mostpart we will assume one actual main machine, and some specialized I/O handling machines.
PURPOSE OF OPERATING SYSTEM THE SHELL EXAMPLE
SHELL COMMANDS (Script Language)Uses System calls for implementation and provided with system, but not part of the operating system
% date >file /*date into file*/
% sort <file1 > file2 /*file1 into sort- result into file2*/=( file2,sort(file1) )
% cat file1 file2 file3 | sort >/dev/lp /* catenate file1, file2 result to file3 to sort then to output=( dev/lp, sort( cat(file1,file2,file3) ) )
% cat file1 file2 file3 | sort >/dev/lp & /*background*/
% ls a*.pdf; /*>=0 */ ls a?.pdf; / ?=1 char*/ ls a[0-9].pdf; /*any of 0 or 1, or ,...,or 9*/
%for fig in *.eps; do ps2pdf $fig; done /*creates pdf files for all eps files*/
EXAMPLES
EXAMPLE OF AN OPERATING SYSTEM SUPPLIED FUNCTIONS - THE SHELL
OPERATING SYSTEM PROVIDES A VIRTUAL MULTIPROCESSOR BY MANAGING RESOURCES
© 2007 M.C. PAULL 2
ACTUAL IO DEVICESMACHINE(S)
ACTUAL
MEMORY(S)
VIRTUAL LARGE MEMORY MULTI-FILE MULTIPROCESSOR MACHINE
OPERATING SYSTEMMANAGES RESOURCESterminals
controller
Disks! Tapes!What are they?I use Files.
It’s nice to havethe computer tomyself
InterpretationsCompilations
libraryOS
x = x + y* z ----> ----> ; mv y,temp; mlt z,temp; add temp,x
os_open
Co
mp
iler+
LibraryR
outines
Code To Find File on disk,( rotate position headetct)bring part of File into MM-etc. this takes time so
+ + + + + +
if (fork() == 0)------> --->P1;
elseP2
MultiProcesses
-->sto “notes”,x1; sto “505“, x2, sto fdloc, y;call libraryforkstub
a[5]=7 ---> --->int a[100); ---> ---> establish location of a[0], say 18
mv 17,temp; add 5,temp; sto* 7,temp.
FilesIO
Dat Def
Arithmetic
stubswitch to supervisor mode
System Calls
User Code
SubroutineandSubroutineCall
returneventually
int *x,*y;int swap(int x,int y)
{int T;T=x; x=y; y=T; }
swap(pt1,pt2) ----->
machine code for swap procedure
load pt1 and pt2 retun address in stacktransfer to machine code for swap
------->return
----->
----->
Compiled Code
Check if resources for new process is available-NO return -1Yes: Allocate a Process Table, and space for
Chilld Process and a Unique pid.Set Child state to “Create” and copy Parent
information into space allocated for Child(including all memory andOpen file information] see (b).return
eventually
Code to set up ANOTHER processes
x=read(fd,buf,byts)------->
+ + + + + +switch to supervisor mode
--> sto &“buf”,x1; sto “byts“, x2, sto fd , y;call libraryread
stub
trap os_open
trap os_open
trap os_open
switch to supervisor modeThe Disk Driver is given fd number. From the in-coreInode in MM and File pointer, it determines the file blockit needs to read and sends this to the Disk ControllerIt blocks the calling process and does a context switch.When interrupt indicating completion arrives it
changes process state to ready
Compiler
Linker
LibraryRoutines
C-code+
LibraryFunctionNames
returneventually
fd= open(“notes/505”) ---> ->sto “notes”,x1; sto “505“, x2, sto fdloc, y; call library-open
#include<stdio>#include<stdlib>
Libraries
Memory
OPERATING SYSTEM CALLS ARE “INTERPRETED” with LIBRARY AND KERNEL CODE© 2005 M.C. PAULL 3
Machine Language
C compiler writtenin Machine code
carries ball & platform
Machine Language Machine Language
Compiler
Machine Language
C compiler writtenin Machine code
C compiler writtenin Machine code
C++ compilerwritten in C code
C++ compilerwritten in C code
OS0
Compilerfor
L1 to L0
Compilerfor L2writtenin
L1
Compilerfor
L2 to L0
Compilerfor L3writtenin
L2
Compilerfor
L3 to L0
Compiler for L1 to L0 Writtenin L0 (Machine Language, ML)
Compilerfor L4writtenin L3
Compiled Code [Compiler]in L0 for L2 to L0
Compiled Codein L0 for L3 to L0 [Compiler]
Compiled Codein L0 for L4 to L0
[Compiler]
Ex:CompilerL0=Machine LangL1=C,L2=C++,L3=JAVA
[C->ML]in ML
[C++->ML]in C
[JAVA->ML]in C++
BOOTSTRAPPING Incremental Development Of Compilers And OS© 2005 M.C. PAULL 4
OS0
HandlesMultiProcesses
ProcessesFor IO
DISK etc
OS0
ProcessesFor Files
OS11-OS1n
OS11-OS1n
FileProcesses
In Cor M. L.
In C++
In C++
THE OPERATING SYSTEM POSITION IN THE COMPUTER LANGUAGE HIERARCHY
Modularity, Information Hiding-Changes in codeand data structure at lower levels do not requirechanges at higher levels--abstraction
© 2005 M.C. PAULL 5
BASIC HARDWARE CONTROLMain memory: get,put, address in MD RegisterAlu:: add, or contents of register alu1 and alu2Disk :: start motor, position head information inregsTimers :: respond after time given in specifiedregister.Gates: between register pairs, virtual mem.
MMU,TLB
Each operation below can be specified by a bit string.Some bit positions represent an operation- otherpositions represent names of devices to be used.Thesebit strings are instructions which manipulate devicesbelow. The operations defined at this level are definedby a sequence of these instructions Those operationsinclude:.reg1--> reg2, reg --> memloc, send memory to fixedaddress on interrupt.
MICRO PROGRAM INSTRUCTION
MACHINE LANGUAGE INSTRUCTIONSEach operation at this level results from a sequence
ofµ-instructions which are called when these are issuedThese instructions must be translatedto their binary equivalents and loadedinto memory. This is done by arudimentary program in binary andBootstrapping*.
ADD r1, r2, r3JMP locMV r, memlocMV r1, r2
BASIC LANGUAGE FEATURESsubroutine calls, and interrupt handling again these
must be handled by an assembler. Develop rudimentarylevel language & bootstrap to higher level:
3
2
1
0
PRIMITIVE MULTIPLE PROCESS HANDLING forkBasic scheduling many processes between blocked
readya, active states, simple communication-shared MM(semaphores) between processes.
BASIC SECONDARY MEM HANDLING I/ODisk: Divers - Positioning heads transfer of data blocks
VIRTUAL MEMORY MANAGEMENT (VM)Paging allow user to assume a memory of size>n MM,
SOPHISTICATED MULTIPLE PROCESSESUsing virtual addresses of processes, files it
can access sophisticated scheduling--priorities,.
PROCESS COMMUNICATION, PIPESMessage Passing Between Processes-Computers
EXTERNAL DEVICES I/O printers, keyboards, monitor
FILES
structured create, destroy, read, write, open, closeAbstract unlike previous memory handling , tree
TABLES: EXTERNAL<->INTERNAL RELATIONSaccess rights
Operating System
Higher Level Assembly Language C, C++
BASIC HARDWARE CONTROL Gates in CPU-IOcontrol-DISK, TIMERS etc.
MICRO PROGRAM INSTRUCTIONSReg Transfers Memory, I/O Control, CPU Functions
MACHINE LANGUAGE INSTRUCTIONSBinary Machine Language-IO-control
BASIC LANGUAGE FEATURES Symbolic Machine --Assembly Language
System Calls, Assembly, Reserved Machine LanguageOperating System
Level i Instructions Call a Sequence OfLevel i-1 Instructions
Application Programs
0
1
2
3
5
6
4
7
Editors CommandCompilersex. EMACS ex. UNIX Shellex. FORTRAN
(+ System Calls + Reserved Machine)
IncrementalDevelopment
Compilers
Ref: Stallings pg69
She walks in beauty, like the nightOf cloudless climes ansd starry skies;
And all thats best of dark and brightMeet in her aspect and her eyes:
Thus melllowed to that tender lightWich heaven to gaudy day denies.
One shade the more, on ray the lessHad half impaired the nameless grace
Which waves in every raven tress,Or softly lightens o’er her face;.................. Byron
Time Sharing-Scheduling
MM
control
nprogs
CPU
computerComputer =Central Command=CPU
MM=Fast Memory
computerdisk->print
computer
computer
card->disk disk->printcomputer
Spooling
MultiProgramming
$end
$run$load
$Fortran
prog
$job id
card->tape tape->printcomputer
operators
bins
programmer operators
punchedcard
MM
control1prog
CPUprog
ComponentsEvents
HISTORY-Some Highlights© 2005 M.C. PAULL 6
So we’ll go no more a-rovingSo late into the night,
Though the heart be still as loving,And the moon be still as bright.
For the sword outwears its sheath,And the soul wears out the breast,
And the heart must pause to breathe,And love itself have rest.
Though the night was made for loving,And the day returns too soon,
Yet we’ll go no more a rovingBy the light of the moon.....Byron
1845 Babbage, Ada Lovelace-Lord Byron*’s Daughter Before Civil War Gears1945 Aiken, Von Neumann US, End Of WW II Relays
Eckert-Maukley US, Zuse Ger., VacuumTuring England(Turing Machine GPC,All Computable Functions, Halting ProbNumerical-Calculations ) ( No Compilers)Binary-Plug Boards--->Punched CardsOne person did all
1955 2nd Gen1965 Assembler Rudementary Compiler Symbolic Addresses: Korean War Transistors
Numerical&Non-Numerical (Compilers-Fortran)(Personell, Inventories, etc) Punched Cards1st
Op Sys: Batch (Background Jobs)
1966 3rd GenOp Sys: CTS, MULTICS (Computer As UTILITY IBM 360)Shared with Many Users (G.E, AT&T, etc.)First Modern OPSys ICsFirst CS DepartmentsMINICOMPUTERS (vs UTILITY)Op Sys: UNIX
1980 4th Gen Microcomputers-PCs LSIOp Sys:One Users CP/M (Sold to user),DOS (Sold to IBM( bundle) B. GatesCommands typed at terminal.Op Sys:GUI-(Mouse, Menus, Icons,
Windows)Englhardt, Invents, XeroxImplements,
Jobs Apple ImplementsMuch later in MicrosoftWindow, SUN X VLSI
Op Sys:Distributed andNetwork Operating
Systems
Tubes
Vietnam War
Mem Cost1 cent/bit
magneticcore
memory
Iraq War I
WAITING(P1)
BUSY(P1) READY(P2)
BUSY(P2)
IDLE
PRINT(P1)
P1 P2PrinterCPUIO
DONE PRINT
P1's P1' P2OSP1'sP1' P2OS
WithI/O
Context SwitchTime for Pi to leave and give control to PjTime To Save State of Pi and give control to Pj
Mono Programming1Process in MM* 2 or more Processes in MM*
© 2007 M.C. PAULL 7
MULTIPROGRAMMING-MANY PROCESS SIMULTANEOUSLY PRESENTEACH GIVEN EPISODES OF CONTINUOUS TIME
P1 P2OS P1 P2OS
NoI/O
Time
1 Efficient Use Of CPU (If IO and CPU can operate in Parallel)2 Problem conceptualization as Parallel Processes
1. Overhead of space, OS code, and Time Penalty Of ContextSwitch (Particularly when it is due to Quanta since the Processcould keep going-(When it is due to IO or mutual exclusion,blockage, etc. Process could not continue).
Multi Programming
Time
* MM=Main Memory=High Speed Memory Of Computer
I/OI/O
Pro
Con
I/O Call
InterruptCompletion
Timeout
WaitingI/O,
Scheduled
Active
Ready
ThreadThread
Thread
quanta
Createsuccessfullycreated
using fork()
Basic Process States
P1 P2 PnPn-1....
Process Shared Mem
Multi-Programming With Threaded Processes
PROCESSES, THREADS, STATES
....ProcessTables
© 2007 M.C. PAULL 8
Threads
ProcessInternal
MEM
stateetc
Pj
OS Scheduler
ThreadScheduler?
Operating System Involvement1 On Sys Calls: I/O, fork, exec,wait, 2 OnQuanta 3 I/O Interrupts
else
exec
I/O
f
proc X proc Y
end
?
read2
read1
write3
I2
end
I3
end
XShell
parent(P) child(ch)
loop
copy-code(cp)
I/O
I1
START a
e
i
j
b
c
d
g
h
k
i m
?
?
?
??
?
?
?
?
?
? Scheduler DecidesClock interrupt I/O I/O interrupt
I/O
end
proc X
statereturnaddr
coreimage
regs...proc Y
statereturnaddr
coreimage
regs...
Process Tables
Scheduler
InterruptHandlerparent
statereturnaddr
coreimage
regs...
Disks,Terminals,Clocks
I/O
...
FileHandler
MEMORY MANAGER
proc X proc Y
end
end
read1
read2
write3
if fork
exec
I1
I2I3
X
Shell
parent
loop
child
cp
START a
ef
i
j
OPERATING SYSTEM
X Y P copy overa A R Rb W A Rc R “ “d R R Ae A R Wf “ “ Rg R R Ah “ “ Af C-Ri A R R Rj W A R R
k R ‘ ‘ “l R -- R Achld
m R -- R -- Acpcdn A -- R -- R
Process
Ev
en
t
States
State Transitions
MULTIPROGRAMMING WITH ONE CPU Single Threaded Processes© 2007 M.C. PAULL 9
I/O
I/OI/Ok
I/O Call
InterruptCompletionTimeout
WaitingI/O,fork,
timeW
Scheduled
ActiveA
ReadyR
quanta
Createsuccessfullycreatedusing fork()
(completion of Ik)Ik
n
?
if fork
elseexec
read2
loop
if fork
~~
overwrite
copy
read2
fork
else
exec
elseexec
elseexec
elseexec
copy-code(cpcd)
overwritecopy
CRIT-1
Process-1 Process-2
CRIT-2Subroutine
Can Share Code In CRITs since only once a CRIT starts thecorresponding Crit can not be started till the first completes
The end ofan instruction
The start of thenext instruction
1
2
CRIT-1
CRIT-3
CRIT-2
Process-2
Process-3CRIT-1
CRIT-2
Process-1
Process-3
True Parrallel In Separate Processors Pseudo-Parrallel In Single Processor
CRIT-3
at the same time Process-2
MDR <--- 1;MAR <--- IR.Shared(IR..<localreg>)<--MEM(MAR);MEM(MAR) <--- MDR
MDR <--- 1;MAR <--- IR.Shared>;(IR..<localreg>)<-- MEM(MAR);MEM(MAR) <--- MDR
Every Sequencing In Parallel Processor Operation In which Instruction executions do not OverlapIs Simulated By A Possible Multiprogramming Sequence: In Multiprogramming the InstructionExecutions are Atomic while in Parallel Operation,of Processors there can be overlap in Instruction executionand even in sub-instruction, i.e., register transfersPARALLEL VS PSEUDO PARALLEL- VALID SEQUENCING OF MUTUALLY EXCLUSIVE
REGIONS CRIT-1 and CRIT-3 are MUTUALLY EXCLUSIVE© 2005 M.C. PAULL 10
mv Shared, locAadd1, locAsto locA Shared
mv Shared, locbsub1, locBsto locB Shared
3Process-1
RegistersTranfersRegisters Tranfers Machine Instructions Machine Instructions
17
Code in CRIT-1 must not overlap with code in CRIT-2
Any overlapping of Register Transfers is possible Any overlapping of complete instructions is possible
1+
2
4
1
3
2
3
0
1
2+
3+
4+
0
4
t+
tt
t
CRIT-1
CRIT-2
CRIT-3
Process-1 Process-2
Process-3
1
3
2
1
2
CRIT-1
CRIT-3
CRIT-2
3
Process-1 Process-2
Process-3
Parrallel Pseudo-Parrallel
PARALLEL VS PSEUDO PARALLEL -INVALID SEQUENCING OFMUTUALLY EXCLUSIVE REGIONS
at the same time
© 2005 M.C. PAULL 11
Every Sequencing In Parallel Processor Operation In which Instruction executionsdo not Overlap Is Simulated By A Possible Multiprogramming Sequence:
If CRIT Consists of 1 Atomic Operation therecannot be a problem
Even If CRIT Consists of 1 Atomic Operation therecan be a problem
18
seperate pointerseven if same file
fork
Parent
Child
file which wasopened beforefork share acommon pointerin Par & Child
same MM till write
openparent
file
openchildfile
COMMON CODEif ( fork() != 0)
{ Parent Code }else{ Child Code }
COMMON CODEif ( fork() != 0)
{ Parent Code }else{ Child Code }
Parent Process
Child Process“Almost Clone”
At this point in Process an “Almost Clone” is produced, “Almost” becausefork() returns Child’s pid to Parent, and at this point returns 0 to Child .
?
If fork() returns -1 the systemwas unable to produceAlmost Clone.
main(){ printf(“my pid is %d\n”, getpid() );
printf(“my parent’s pid is %d\n”, getppid() );printf(“my group pid is %d\n”, getpgrp() );}
OS action on System Call: fork:Is resources for new Process available?-NO return -YES:1 Allocate a Process Table, and space for
Child Process and a Unique pid.2 Set Child state to “Create”and3 Copy Parent information into space
allocated for Child(including all memoryand Open file information] see (b) below
© 2005 M.C. PAULL 12UNIX PROCESS CREATION, THE FORK
?fork
Note: Information can be passed bewteen Processes thru a File, but not through MM as normally declared.(b)
About IDs
(a)
?fork
fork
Parent Process
(a)Child Process“Almost Clone”
forkParent Process
execve
Child Process cmd Process
Parent Process
cmd Process
Parent Process
while(TRUE){ type_prompt();
read_cmd(cmd, parameters)
if (fork() != 0){ /*Parent code*/
waitpid(-1, &status,0);}
else{ /*Child code*/
execve(cmd, pars,0);}
}
waitpid
waitpid
Periods When Child Does Not Exist
Periods When Parent is is stopped at waitpid
Possible Sequence of CPU ActivityPar Child Cmd Par Child Cmd Par Child Cmdfork
Even though there are a number of different Processes involved only one is runnable at anyinstant,the others are either non-existent or in waiting mode during that time. This is not pseudoparalleloperation. Its more like Parent is calling a subroutine, or making a system call. The shelldesigner is scheduling the involved Processes herself.
SHELL STRUCTURES USING FORK
fork(Par and Child in MM Either one may run first)
FORK, WAITPID, EXECVE
Child Cmd Par Child Cmd Par Child Cmd Parfork Possible Sequence of CPU Activity
© 2005 M.C. PAULL 13
Periods When Child Does Not Exist
Periods When Parent is is stopped at waitpid
fork()
parent code
waitpid(-1,&status,0)
child code
read_cmd(cmd,pars)
execve(cmd,pars,0)
fork()
parent code
waitpid(-1,&status,0)
child code
read_cmd(cmd,pars)
=0
execve(cmd,pars,0)
fork()
parent code
waitpid(-1,&status,0)
child code
read_cmd(cmd,pars)cp f1 f2
cmd: cppar1: f1par2: f2 =0
execve(cmd,pars,0)
fork()
parent code
waitpid(-1,&status,0)
child code
read_cmd(cmd,pars)
execve(cmd,pars,0)
fork()
parent code
waitpid(-1,&status,0)
child code
read_cmd(cmd,pars)
cmd: cppar1: f1par2: f2
execve(cmd,pars,0)
fork()
parent code
waitpid(-1,&status,0)
child code
read_cmd(cmd,pars)
=0
cmd: cppar1: f1par2: f2
execve(cp,f1,f2,0)
=0=0
=0
=0
GENERATE
main(3,ad,0)
ad:end
exit
main(3,ad,0)
cpf1f2
ad:end
exit
main(3,ad,0)
ad: cpf1f2
end
REPLACE
exit
main(3,ad,0)
ad:end
exit
cmd: cppar1: f1par2: f2
A SHELL USING FORK-TRACE
Immediately after the fork, parent and child have identical memory contents(until a store by either). Also they both have all files opened before the forkand have a common pointer to their location in these files.
© 2005 M.C. PAULL 14
childpid= 0
fork
Par
fork
Par(Par) Par(Child)
Child
Par1Par)
fork
Par
ChildPar) Child(Child)
Child
fork
fork
Parent
Child
file which wasopened beforefork share acommon pointerin Par & Child
same MM till write
openparent
file
openchildfile
seperate pointerseven if same file
COMMON CODEif ( fork() != 0)
{ Parent Code }else{ Child Code } fork() returns 0 in child
fork() returns >0 (childs pid) in parent
(c)(b)
CREATING PROCESSES FORK PARENT-CHILD RELATIONS© 2005 M.C. PAULL 15
Par1(Child)
cond
Par2(Child)Par2(Par)
(a)
COMMON CODEif( fork() != 0)
{ Par }else
/*Child*/{ if( fork() != 0)
{ Child(Par) Code }else
{ Child(Child) }}
COMMON CODEif( fork() != 0){ /*Par*/if( fork() != 0) }Par(Par) }
elsePar(Child) }
else{Child }
COMMON CODEif(cond)
/*Par1 */{ if( fork() != 0)
{Par1(Par) }else{ Par1(Child) }
}else
/*Par2*/{ if (fork() != 0)
{ Par2(Par) }else{ Par2(Child) }
}
USES OF TWO FORKS
FORK BASICS
fork fork
Par1 Par2
. . .
. . .
. . .
Application Code
CLibrary Functions
OS Kernel
system callslibrary calls
system calls
User Process
context switch
© 2005 M.C. PAULL 16
UNIX OPERATING SYSTEM CALLS, LIBRARY FUNCTIONS, IPC
Through File or “Pipe” (On Disk)
DISK
Through Shared Memoryset up through OS
P1 Signals Through OS To P2Set Up in P2 through OS detected by P2as soon as it runs no matter where it isin its Process.
Exceptions can be detected anywherewithin the run of the Process
SYNCHRONOUS(OCCURENCE WHERE SPECIFIED IN CODE)
ASYNCHRONOUSCan interrupt Process anywhere within aProcess sending control to a Handler Routine
INTER-PROCESS COMMUNICATION UNIX
C-code+
LibraryFunctionNames
Compiler
Linker
LibraryRoutines
S=Shared
mv S,L2mv S,L2
read Fwrite F
signalOS
OS
OS
pipe fd[0]fd[1]
Parent fd[1]fd[0] Childpipe
X
X
Parent fd[1]fd[0]
Childpipe
Inter Process Communication Through A Pipe
Initially: access to both sides of pipe
#include “ourhdr.h”#define MAXLINE 1024int main(void);{ int fd[2];
pid_t pid;char line[MAXLINE];if ( pipe(fd) < 0 ) err_sys(“pipe error”); /*open-no name*/
if ( (pid = fork() ) < 0 ) err_sys(“fork error”);else
{ if (pid > 0){ /*parent code */
close( fd[0] );write(fd(1), “hello world\n”, 12); };
else{ /*child code */
close( fd[1] );n = read(fd(0), line, MAXLINE); };
}exit(0);
}
[Before Fork]
IPC: PIPES and FILESMutual Exlusive Access To Shared Memory Achieved by Passing All Requests (read writes) from
Involved Processes to be Executed by a ANOTHER (THIRD PARTY) Single Process (usually the kernel):In general pipes are circular buffers through which communication between two Processes is
established. When a pipe is created it is given a fixed size, (~4k bytes). A write of any length, or readrequest from a Process is executed atomically,i.e., mutually exclusively. If a pipe write will overflowthe pipe, or a read sees an empty pipe the Process will block or optionally returns a value which indicateswhether it worked. It behaves like a File (assumming that two references to a the same File by twoProcesses are mutually exclusive) with reads and writes of the same form, but unlike a File, thedata is stored can be MM in the kernel-making access to it faster and the restricted point of access forreading and writing. Like accessing Files the required mutual exclusion of reads and writes is achievedby having one Process, the handling requests from different Processes , executing one at a time.
When IPC is done with pipes the information is read out in the order it was written. Data is read and writtenin fixed size units. Pipes are read and written in sizes consistent with the maximum contents of the pipe andaccess to specified memory is atomic with respect to other accesses to the same specified memory
into pipe
OS out
int fd;char buf[7];
fd=open(/paull/inoutfile,RWONLY) /*open by name*/write(fd, “test it”, 7);read(fd, buf, 7);
File/paull/inoutfile
#include <unlistd.h>int fd[2];char buf[7];
pipe(fd); /*open-no name*/write(fd[1], “test it”, 7);read(fd[0], buf, 7);
PIPE (anonymous) In SINGLE PROCESS FILE IN SINGLE PROCESS
fd
pipefd[0]
fd[1]
Process
MORE ABOUT IPC WITH PIPES© 2007 M.C. PAULL 17
TOPIC: INPUT-OUTPUT BACKGROUND HARDWARE:
If instruction is not in cache-page faultop sys must get instruction
Interrupt test aftereach machine instr.
interruptor trap-on which
instruction?
MMCPU FetchDecodeEx
Fetch Decode Ex
Fetch Decode Ex
Ex
Ex
Buffer
Simple
Pipelined
SuperScalar
Fetch Decode
Fetch Decode
CONTROL
ALUREGS
IO
micro-code
Operating System Works Directly With IO
With DMAMM buffermust not
be swapped
Video
VideoController
RAM
PrinterController
DISK
(driver) sectors, tracks, cylinder,
(user) read, write, file
(controller) move arms, heads, detect block#
DiskController
InterruptController
GpRegsPrgCntr StckPtr
PrgStatWd
InstrReg
On Chip Mem
Cache 1Cache 2
MainMem
BRIDGE
printerdriver
diskdriver
Op Sys
Graphics Adapter
DMA
C P U(Active Process)
© 2005 M.C. PAULL 18
User I/O -> Drivers -> Controller -> Device
RAM
Disk Cache
I/OBuffer
MM Mngmnt
MM Mngmnt
ChangingScreenContolWordsPictures
I/O Call
IO Interrupt
Timeout(quantaused up)
WaitingI/O,
Sch
edul
edActive
Ready
Sleep(time)
Semaphor(down)
Page Fault
Page FaultFixed
Waitingtime xwaitpid
Timeout
up
WaitingExit
WaitingPage Flt
WaitingSemaphor
Createsuccessfullycreatedusing fork()
Scheduling:time consumedpriority
Memory:Page Tablestext,data,stackdisk loc
Event AwaitedState
Identity
Signals
PID,UID,GID
Blocked, SentRegisters SavedSystem Call Info
File Descriptor Tbl
AccountingCPU time usedLimits
fd
Process Table
fd
Must maintain much info for each Active Process
Process States
TOPICS: PROCESSES , DEADLOCK
Proc B
Proc CProc A’
Deadlock
wait(x)
signal(y)
wait(y)
signal(x)
Monitor: Higer Level Construct for
Holds
Needs
Proc A Proc B Proc C
CommonMemory*
fork Message
IPC Inter-Process Communication
Proc A’
*Not Global-Must Be SpeciallyDeclared.
CRIT
CRIT
CRIT Protection:Mutual Exclusion-Synchronization
semaphors, tsl, Peterson
Par
Chld
© 2005 M.C. PAULL 19
SCHEDULING
J3J4J5J1
0 1 2 3 4 5 6 7 8 9
Arriv
als
Shortest First Optimal
J2 turnaround
Turnaround=(1+2+3+5+9)/5=20/5=4
wr wrWITH I/O
97 |--- 6 ---| 91 |---5--| 109 109 109 109tmrd rd(6/5)90
80 80 80 80 |--- 6---| 74 74
90 90 90 |--4--| 135 135 |---6---| 129(6/4)90
MainMemory(MM) RAM
..
......
....
....
....
MainMemory
RAMPartitionedInto Pages
}Page
MM
...
....
....
..
...
....
....
DISK
Virtual Memory} Page
...
....
....
VM
Partitioned Into Pages Paged & Virtual Memory
VM address
MMaddress
page|offset
page
DATA STRUCTURESTo Transform
VM to MM Address
to MMaddress
contains V address
PageTable
Inverted(Hashed)
PageTable
TOPIC: MEMORY MANAGEMENT (PROCESSES CONTINUOUS AND PAGED
offset
Pg Tbl Size, MM Page Access/ReplacementSpeed Page Replacement Algs
..
..
outin
freeList
..
© 2005 M.C. PAULL 20
DATA STRUCTURESTo Record Locations
Of Holes And Processes
LinkedLists
BuddyAlgorithm
011000111
..
.
Bit Map MemoryBlocks
2n
Holes and Processes
MM
hole
process
Finding A Hole Of Sufficient Size ReconstitutingHoles When Process Leaves
Indexed by VMaddr
MS-DOS SYSTEM
DISK BLOCKS IN FILE
sampts tolinkedlin MMtable(1entry/block)
sally
Notestel#s
class/sam
/sally
416344
pic4txt
/sally/Notes
416505
/sam/notes
pic4txt
/sally/Notes/416
sam
/sally/tel#s
link(“/sam/notes/416" “sally/Notes/416")
/sam/notes/505 416505
/notes
/dev/fd0/notes/505
root
notes
mount(“/dev/fd0/notes”,”/sam/notes“ ,0)
DISK
notes
Links Hard and Symbolic
/dev/fd0
UNIX
I-NodesPoints to
Disk BlocksIn File
root
File Name: /sam/notes/505Working Directory: cd /sam
fd = open(“sally/notes/505”, O_RDONLY)n = read(fd, buffer, nbytes)
Special Files-DevisesBlock: Disk, /dev/hdlCharacter: Keyboard /dev/tty
Permanent or Semi-Permanent Recording Of:Information:Text,Program,Tables,Drawings,etc
A FILE IS
File Table/Process
in core file info
TOPIC: FILES© 2005 M.C. PAULL 21
UNIX and CP/M Point to Blocks,UNIX Indirectly CP/M Directly
DISK BLOCKS IN FILE
Link
File Structure On Disk
Data
Directory
System Calls For Files
File’s Name Associated With Disk Blocks Containing File
sampts toINODEwhich points toDisk Blocks in sam
K1 K1
K2
K2
K3
K3
Secret Key
PrK1
PubK2 Pub
K 2
PubK1
PrK2
PubK 3
PubK1PrK3
PubK3
Public Key
Encryption
f (s)
f f (s)-passwd 4
f f f (s)-passwd 3
f f f f (s)-passwd 2
f f f f f (s)-passwd 1
f f f f f f (s)=e-givenf-1(e)
f-1f-1(e)
f-1f-1f-1(e)
f-1f-1f-1f-1(e)
f-1f-1f-1f-1f-1(e)
Hard
Easy
apply f(given)
fe 1(f-1(e))
initiallyknows e,f 2 f-1f-1(e) 3 f-1f-1f-1(e) 4 f-1f-1f-1f-1(e) 5 f-1f-1f-1f-1f-1(e)
1 f f-1(e )= e OK
2 f f-1f-1(e) = f-1(e)
3 f f-1f-1f-1(e) = f-1f-1(e)
4 f f-1f-1f-1f-1(e) = f-1f-1f-1(e)
5 f f-1f-1f-1f-1f-1(e) = f-1f-1f-1f-1(e)
1-Way (Trap-Door) Functions For Passing Password By Wire or Air
name Encrypted Password
paull
rbackwani
brussell
Unix Basic Password Table (Plan For Breakin Foiled!)
TOPIC: SECURITY
f
© 2005 M.C. PAULL 22
namepassword
encrypt
ξψζ....345 ωθρpaull
yesyes
1 or 2 / pair2 / individual
Passwords
1-way
(with inverse)
To All
DataText1Text2Text3
OpenFiles
REGsPC:
Stack
REGsPC:
Stack
REGsPC:
Stack
UShared
process- iThread1 Thread2 Thread3
Data
Text
OpenFiles
REGsPC:
Stack
process-jindependent
Virtual Parallel Machine
TWO TYPES OF CONTEXT SWITCHES -PROCESS MUCH MEMORY SLOWSWITCH, THREAD LESS MEMORY SWITCH FAST SWITCH IMPROVED EFFICIENCY
I/OCompute
KERNEL
100 t0 1
Thread Quanta
I/O, Pg Flt, I/O, Pg Flt,
Data
Text1Text2
OpenFiles
REGsPC:
Stack
REGsPC:
Stack
UShared
process-kThread1 Thread2
I/O, Pg Flt,Thread Quanta
Virtual 3-CPU independent Parrallel MachineVirtual 2-CPU Parrallel MachineVirtual 1-CPU Parrallel Machine
sharedmemory ?
© 2005 M.C. PAULL 23
THREADS (GLOBAL MEMORY, CONTROL OS OR PROCESS)
Control (Scheduling): In Process? or In Kernel(OS) ?(Kernel must handle IO)
SHARED MEMORY MULTIPLE PROCESSOR COMPUTER
lock os
UserProcesses
system calls-acquire lock
IOlock
lock lock
MM
CPU 1 CPU 2 CPU nCPU 0
CPU 0 CPU 1 CPU 2 CPU ncache
IO
MM
LocalMemory
cache cachecache
LocalMemory
LocalMemory
LocalMemory
SHARED MEMORY PROCESSORS AND THEIR OPERATING SYSTEMS© 2005 M.C. PAULL 24
1 OS
1 Process at a time goes to OS (Bottleneck)
If Processes use different parts of OS then > 1 can go. Problem with interference.
![Unix System Calls [相容模式] - ntnu.edu.tw](https://img.dokumen.tips/doc/110x75/6197442fee2c1e380077e7fa/unix-system-calls-ntnuedutw.jpg)
