Working with the Unix OS

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Buffer Cache The kernel places the buffer at the end of the free list, unless an I/O error occurred or is marked old, in which case it places the buffer at the beginning of the free list. The kernel raises the processor execution level to prevent disk interrupts while manipulating the free list, thereby preventing corruption of the buffer pointers. Figure 67. Second Scenario for Buffer Allocation When the asynchronous write completes, the kernel releases the buffer and places it at the head of the free list. Figure 68. Third Scenario for Buffer Allocation 183
Buffer Cache Figure 69. Forth Scenario for Buffer Allocation No buffers available so process goes to sleep. Figure 70. Race for Free Buffer . If process A attempts to read a disk block and allocates a buffer as in (2), then it will sleep while it waits for the I/O transmission from disk to complete. While process A sleeps, suppose the kernel schedules a second process B, which tries to access the disk block whose buffer was just locked by process A. Figure 71. Fifth Scenario for Buffer Allocation 184
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UNIVERSITY OF ATHENS DEPARTMENT OF
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Figure 27. Driver Entry Points.....
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Introduction to Unix ! Execution ma
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Introduction to Unix It works in th
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Introduction to Unix * matches 0 or
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Introduction to Unix vi file-name s
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Introduction to Unix 1,$s/^/>>/ 1,$
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Introduction to Unix ! Special Devi
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Introduction to Unix Working with F
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Introduction to Unix ! Communicatio
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Unix Shells 2. UNIX SHELLS Back Quo
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Unix Shells ! CASE Statement case t
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Unix Shells two lines !Y@Y@Z@Z@ZY c
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Unix Shells if $append then tee -a
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C Programming - Basics main() { int
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C Programming - Basics e.g. i += 2
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External Variables A C program cons
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C Programming - Basics main.c #incl
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C Programming - Basics default: pri
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C Programming - Basics struct tnode
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Unix Tools 4. UNIX TOOLS Tools of t
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Unix Tools Korn shell ! .profile HI
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Unix Tools grep "$name" $PHONEBOOK
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Unix Tools awk '$3 > 0 { print $1,
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Unix Tools END { print max, maxline
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Unix Tools Let an example input fil
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Unix Tools Brown eqn 1 # output Jon
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Development Tools Make looks at the
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Development Tools /* compute size o
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Development Tools #endif #line cons
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Development Tools 1.1 5 lines Retri
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Development Tools In Emacs, you may
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Development Tools */ %{ #define YYS
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C Libraries 6. C LIBRARIES Input an
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C Libraries } while (!feof(fp1)) pu
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C Libraries } free(p); /* what is w
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C Libraries } if ((fp->flag&( _READ
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C Libraries /* dirwalk: apply fcn t
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C Libraries } switch (pid=fork()){
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C Libraries What is curses? - libra
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C Libraries } if ((fd=fopen(argv[1]
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Introduction to kernel 7. INTRODUCT
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82 Introduction to kernel Programs
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Introduction to kernel } { printf("
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Introduction to kernel The kernel r
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Introduction to kernel UNIX Interna
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Introduction to kernel File System
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Introduction to kernel Every proces
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Processes I Process States 1. Execu
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Processes I } printf("%d %s\n", cnt
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Processes I dup (and other similar
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Processes I The u area contains - p
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Processes I The Context of a Proces
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Processes I Process Control use and
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Processes I Although the processes
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Processes I Handling Signals - proc
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Processes I USER=neville PATH=/user
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Processes I ! Shadow Password /etc/
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struct timeval { long tv_sec; /* se
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Processes I F_SETFL set status flag
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Processes I process is the child pr
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Processes I Rules about sharing of
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Processes II 9. PROCESSES (II) FORK
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Processes II /* background.c */ #in
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Processes II } while (1){ printf("p
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Processes II } /* child */ signal (
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Processes II int readline(int fd, c
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Page 139 and 140: Processes II System V IPC - message
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Page 149 and 150: I/O Subsystem Terminal Drivers - In
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Page 157 and 158: Interprocess Communication } { ptra
Page 159 and 160: Interprocess Communication T ID KEY
Page 161 and 162: Interprocess Communication }; int m
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Page 165 and 166: Interprocess Communication /* struc
Page 167 and 168: Interprocess Communication ! Compar
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Page 171 and 172: Interprocess Communication Address
Page 173 and 174: Process Scheduling Page Tables and
Page 176 and 177: Figure 49. Tie breaker rule Process
Page 178 and 179: Process Scheduling Clock - restart
Page 180 and 181: Process Scheduling Figure 57. Mappi
Page 182 and 183: Figure 62. Sequence of Swapping Ope
Page 184 and 185: Buffer Cache The kernel takes buffe
Page 188 and 189: Buffer Cache Process B will find th
Page 190 and 191: Unix Administration 14. UNIX ADMINI
Page 192 and 193: Unix Administration Example output
Page 194 and 195: Unix Administration *) IN=-mtime -2
Page 196 and 197: Unix Administration Load /Unix kern
Page 198 and 199: Unix Administration for (i=0; i&i d
Page 200 and 201: Unix Administration fi done echo $s
Page 202 and 203: Unix Administration New Software !
Page 204 and 205: Unix Security Example: group name:g
Page 206 and 207: Unix Security $ crypt < exam320.Z >
Page 208 and 209: Unix Security - exported filesystem
Page 210 and 211: Unix Security system(cmdstr); $ ech
Page 212: Unix Security - repairs damaged use
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