lec2 drgfhfjbhnvgProcesses_extra.pptx.pptx

This is extra info for processes

1. Ch3: processes extra lecture

2. P ro ce ss e s The P ro ce ss M ode l M ultiprogr a mm i ng of four progr a m s Conce ptu a l mode l of 4 ind e p e nd e nt , s e qu e nt i a l pro ce ss e s O nl y one progr a m ac tive a t a ny i ns t a nt 2

3. 3 P ro ce ss Ta b le Whe n a proces s move s fro m a runnin g state t o a read y o r blocke d stat e i t mus t store certai n informatio n s o tha t i t ca n restar t from th e s ame point w he n i t m ove s bac k t o a runni ng s t a te Whic h instructio n i t wa s abou t t o execute Whic h recor d i t wa s abou t t o rea d fro m it s input file Value s i n th e registers

4. P ro ce ss Con trol B l oc k F iel ds of a pro ce ss t a ble e nt ry 4

5. U n i x P ro ce ss S tate T r a ns iti ons 5

6. 6 U n i x P ro ce ss S tate s Exec uti ng i n us e r mode . Exec uti ng i n ke rn e l m ode . N ot exec uti ng but r ea dy t o run w he n s che dul e d. S l ee pi ng (blo cke d) i n m a i n m e m ory. R ea dy, but sw appe d out t o di s c . S l ee pi ng, but sw appe d out t o di s c .

7. 7 U n i x P ro ce ss S tate s (2) R e turni ng from the ke rn e l t o us e r mode , but th e n pr eempte d (s i m il a r t o s t a te 3). N e w l y c r ea t e d a nd i n a tr a ns iti on s t a t e . It e xi s t s but i s not r ea dy t o run nor i s it s l ee pi ng. H a s exec ut e d e xit () a nd i s a zombie . It no l onge r e xi s t s but l eave s a r ec ord of e xit code a nd t i m i ng s t a t s for it s pa r e nt .

8. M u c h M or e in / p r o c $ ca t /proc/pc i PC I device s found : Maste r Capable . N o bursts . Mi n Gnt=2 . Bu s , Clas s IR Q devic e 2 , functio n : 0300 : PC I devic e 8086:258 2 (re v 4) . 11 . Non-prefetchabl e 3 2 bi t memor y a t 0xdff0000 [0xdff7f f I/ O a t 0xe89 8 [0xe89f] . . . . Bu s , devic e , functio n : Clas s 0600 : PC I devic e 8086:258 (re v 4) . Bu s , devic e 1 , functio n : Clas s 0604 : PC I devic e 8086:258 1 (re v 4) . IR Q 11 .

9. Can a process create a process ? Yes! Unique identity of process is the “process ID” (or PID) Fork() system call creates a copy of current process with a new PID Return value from Fork(): integer When > 0: Running in (original) Parent process return value is pid of new child When = 0: Running in new Child process When < 0: Error! Must handle somehow Running in original process All state of original process duplicated in both Parent and Child! Memory, File Descriptors (next topic), etc…

10. f ork1.c #include < stdlib.h > #include < stdio.h > #include < string.h > #include < unistd.h > #include <sys/ types.h > #define BUFSIZE 1024 int main( int argc , char * argv []) { char buf [BUFSIZE]; size_t readlen , writelen , slen ; pid_t cpid , mypid ; pid_t pid = getpid (); /* get current processes PID */ printf ("Parent pid : %d\n", pid ); cpid = fork(); if ( cpid > 0) { /* Parent Process */ mypid = getpid (); printf ("[%d] parent of [%d]\n", mypid , cpid ); } else if ( cpid == 0) { /* Child Process */ mypid = getpid (); printf ("[%d] child\n", mypid ); } else { perror ("Fork failed"); exit(1); } exit(0); }

11. fork1.c output Parent  pid : 502                                                                                                                                                           [502] parent of [503]                                                                                                                                                     [503] child 

12. UNIX Process Management UNIX fork – system call to create a copy of the current process, and start it running No arguments! UNIX exec – system call to change the program being run by the current process UNIX wait – system call to wait for a process to finish UNIX signal – system call to send a notification to another process UNIX man pages: fork (2), exec (3), wait (2), signal (3)

13. f ork2.c int status; … cpid = fork(); if ( cpid > 0) { /* Parent Process */ mypid = getpid (); printf ("[%d] parent of [%d]\n", mypid,cpid ); tcpid = wait(&status); printf ("[%d] bye %d(%d)\n", mypid , tcpid , status); } else if ( cpid == 0) { /* Child Process */ mypid = getpid (); printf ("[%d] child\n", mypid ); } …

14. 389] parent of [390]                                                                                                                                                                                          [390] child                                                                                                                                                                                                    [389] bye 390(0)

15. UNIX Process Management

16. Process Races: fork3.c Question: What does this program print? Does it change if you add in one of the sleep() statements? int i ; cpid = fork(); if ( cpid > 0) { mypid = getpid (); printf ("[%d] parent of [%d]\n", mypid , cpid ); for ( i =0; i <100; i ++) { printf ("[%d] parent: %d\n", mypid , i ); // sleep(1); } } else if ( cpid == 0) { mypid = getpid (); printf ("[%d] child\n", mypid ); for ( i =0; i >-100; i --) { printf ("[%d] child: %d\n", mypid , i ); // sleep(1); } }

17. Hello World[524] parent of [525] [524] parent: 0 [524] parent: 1 [524] parent: 2 [524] parent: 3 [524] parent: 4 [524] parent: 5 [524] parent: 6 [524] parent: 7 [524] parent: 8 [524] parent: 9 [524] parent: 10 [524] parent: 11 [524] parent: 12 [524] parent: 13 [524] parent: 14 [524] parent: 15 [524] parent: 16 [524] parent: 17 [524] parent: 18 [524] parent: 19 [524] parent: 20 [524] parent: 21 [524] parent: 22 [524] parent: 23 [524] parent: 24 [524] parent: 25 [524] parent: 26 [524] parent: 27 [524] parent: 28 [524] parent: 29 [524] parent: 30 [524] parent: 31 [524] parent: 32 [524] parent: 33 [524] parent: 34 [524] parent: 35 [524] parent: 36 [524] parent: 37 [524] parent: 38 [524] parent: 39 [524] parent: 40 [524] parent: 41 [524] parent: 42 [524] parent: 43 [524] parent: 44 [524] parent: 45 [524] parent: 46 [524] parent: 47 [524] parent: 48 [524] parent: 49 [524] parent: 50 [524] parent: 51 [524] parent: 52 [524] parent: 53 [524] parent: 54 Hello World[525] child [524] parent: 55 Hello World[524] parent of [525] [524] parent: 0 [524] parent: 1 [524] parent: 2 [524] parent: 3 [524] parent: 4 [524] parent: 5 [524] parent: 6 [524] parent: 7 [524] parent: 8 [524] parent: 9 [524] parent: 10 [524] parent: 11 [524] parent: 12 [524] parent: 13 [524] parent: 14 [524] parent: 15 [524] parent: 16 [524] parent: 17 [524] parent: 18 [524] parent: 19 [524] parent: 20 [524] parent: 21 [524] parent: 22 [524] parent: 23 [524] parent: 24 [524] parent: 25 [524] parent: 26 [524] parent: 27 [524] parent: 28 [524] parent: 29 [524] parent: 30 [524] parent: 31 [524] parent: 32 [524] parent: 33 [524] parent: 34 [524] parent: 35 [524] parent: 36 [524] parent: 37 [524] parent: 38 [524] parent: 39 [524] parent: 40 [524] parent: 41 [524] parent: 42 [524] parent: 43 [524] parent: 44 [524] parent: 45 [524] parent: 46 [524] parent: 47 [524] parent: 48 [524] parent: 49 [524] parent: 50 [524] parent: 51 [524] parent: 52 [524] parent: 53 [524] parent: 54 Hello World[525] child [524] parent: 55 [525] child: 0 [524] parent: 56 [525] child: -1 [524] parent: 57 [525] child: -2 [524] parent: 58 [525] child: -3 [524] parent: 59 [525] child: -4 [524] parent: 60 [525] child: -5 [524] parent: 61 [525] child: -6 [524] parent: 62 [525] child: -7 [524] parent: 63 [525] child: -8 [524] parent: 64 [525] child: -9 [524] parent: 65 [525] child: -10 [524] parent: 66 [525] child: -11 [524] parent: 67 [525] child: -12 [524] parent: 68 [525] child: -13 [524] parent: 69 [525] child: -14 [524] parent: 70 [525] child: -15 [524] parent: 71 [525] child: -16 [524] parent: 72 [525] child: -17 [524] parent: 73 [525] child: -18 [524] parent: 74 [525] child: -19 [524] parent: 75 [525] child: -20 [524] parent: 76 [525] child: -21 [524] parent: 77 [525] child: -22 [524] parent: 78 [525] child: -23 [524] parent: 79 [525] child: -24 [524] parent: 80 [525] child: -25 [524] parent: 81 [525] child: -26 [524] parent: 82 [525] child: -27 [524] parent: 83 [525] child: -28 [524] parent: 84 [525] child: -29 [524] parent: 85 [525] child: -30 [524] parent: 86 [525] child: -31 [524] parent: 87 [525] child: -32 [524] parent: 88 [525] child: -33 [524] parent: 89 [525] child: -34 [524] parent: 90 [525] child: -35 [524] parent: 91 [525] child: -36 [524] parent: 92 [525] child: -37 [524] parent: 93 [525] child: -38 [524] parent: 94 [525] child: -39 [524] parent: 95 [525] child: -40 [524] parent: 96 [525] child: -41 [524] parent: 97 [524] parent: 98 [524] parent: 99 [525] child: -42 [525] child: -43 [525] child: -44 [525] child: -45 [525] child: -46 [525] child: -47 [525] child: -48 [525] child: -49 [525] child: -50 [525] child: -51 [525] child: -52 [525] child: -53 [525] child: -54 [525] child: -55 [525] child: -56 [525] child: -57 [525] child: -58 [525] child: -59 [525] child: -60 [525] child: -61 [525] child: -62 [525] child: -63 [525] child: -64 [525] child: -65 [525] child: -66 [525] child: -67 [525] child: -68 [525] child: -69 [525] child: -70 [525] child: -71 [525] child: -72 [525] child: -73 [525] child: -74 [525] child: -75 [525] child: -76 [525] child: -77 [525] child: -78 [525] child: -79 [525] child: -80 [525] child: -81 [525] child: -82 [525] child: -83 [525] child: -84 [525] child: -85 [525] child: -86 [525] child: -87 [525] child: -88 [525] child: -89 [525] child: -90 [525] child: -91 [525] child: -92 [525] child: -93 [525] child: -94 [525] child: -95 [525] child: -96 [525] child: -97 [525] child: -98 [525] child: -99 Hello World[524] parent of [525] [524] parent: 0 [524] parent: 1 [524] parent: 2 [524] parent: 3 [524] parent: 4 [524] parent: 5 [524] parent: 6 [524] parent: 7 [524] parent: 8 [524] parent: 9 [524] parent: 10 [524] parent: 11 [524] parent: 12 [524] parent: 13 [524] parent: 14 [524] parent: 15 [524] parent: 16 [524] parent: 17 [524] parent: 18 [524] parent: 19 [524] parent: 20 [524] parent: 21 [524] parent: 22 [524] parent: 23 [524] parent: 24 [524] parent: 25 [524] parent: 26 [524] parent: 27 [524] parent: 28 [524] parent: 29 [524] parent: 30 [524] parent: 31 [524] parent: 32 [524] parent: 33 [524] parent: 34 [524] parent: 35 [524] parent: 36 [524] parent: 37 [524] parent: 38 [524] parent: 39 [524] parent: 40 [524] parent: 41 [524] parent: 42 [524] parent: 43 [524] parent: 44 [524] parent: 45 [524] parent: 46 [524] parent: 47 [524] parent: 48 [524] parent: 49 [524] parent: 50 [524] parent: 51 [524] parent: 52 [524] parent: 53 [524] parent: 54 Hello World[525] child [524] parent: 55 [525] child: 0 [524] parent: 56 [525] child: -1 [524] parent: 57 [525] child: -2 [524] parent: 58 [525] child: -3 [524] parent: 59 [525] child: -4 [524] parent: 60 [525] child: -5 [524] parent: 61 [525] child: -6 [524] parent: 62 [525] child: -7 [524] parent: 63 [525] child: -8 [524] parent: 64 [525] child: -9 [524] parent: 65 [525] child: -10 [524] parent: 66 [525] child: -11 [524] parent: 67 [525] child: -12 [524] parent: 68 [525] child: -13 [524] parent: 69 [525] child: -14 [524] parent: 70 [525] child: -15 [524] parent: 71 [525] child: -16 [524] parent: 72 [525] child: -17 [524] parent: 73 [525] child: -18 [524] parent: 74 [525] child: -19 [524] parent: 75 [525] child: -20 [524] parent: 76 [525] child: -21 [524] parent: 77 [525] child: -22 [524] parent: 78 [525] child: -23 [524] parent: 79 [525] child: -24 [524] parent: 80 [525] child: -25 [524] parent: 81 [525] child: -26 [524] parent: 82 [525] child: -27 [524] parent: 83 [525] child: -28 [524] parent: 84 [525] child: -29 [524] parent: 85 [525] child: -30 [524] parent: 86 [525] child: -31 [524] parent: 87 [525] child: -32 [524] parent: 88 [525] child: -33 [524] parent: 89 [525] child: -34 [524] parent: 90 [525] child: -35 [524] parent: 91 [525] child: -36 [524] parent: 92 [525] child: -37 [524] parent: 93 [525] child: -38 [524] parent: 94 [525] child: -39 [524] parent: 95 [525] child: -40 [524] parent: 96 [525] child: -41 [524] parent: 97 [524] parent: 98 [524] parent: 99 [525] child: -42 [525] child: -43 [525] child: -44 [525] child: -45 [525] child: -46 [525] child: -47 [525] child: -48 [525] child: -49 [525] child: -50 [525] child: -51 [525] child: -52 [525] child: -53 [525] child: -54 [525] child: -55 [525] child: -56 [525] child: -57 [525] child: -58 [525] child: -59 [525] child: -60 [525] child: -61 [525] child: -62 [525] child: -63 [525] child: -64 [525] child: -65 [525] child: -66 [525] child: -67 [525] child: -68 [525] child: -69 [525] child: -70 [525] child: -71 [525] child: -72 [525] child: -73 [525] child: -74 [525] child: -75 [525] child: -76 [525] child: -77 [525] child: -78 [525] child: -79 [525] child: -80 [525] child: -81 [525] child: -82 [525] child: -83 [525] child: -84 [525] child: -85 [525] child: -86 [525] child: -87 [525] child: -88 [525] child: -89 [525] child: -90 [525] child: -91 [525] child: -92 [525] child: -93 [525] child: -94 [525] child: -95 [525] child: -96 [525] child: -97 [525] child: -98 [525] child: -99 Hello World[524] parent of [525] [524] parent: 0 [524] parent: 1 [524] parent: 2 [524] parent: 3 [524] parent: 4 [524] parent: 5 [524] parent: 6 [524] parent: 7 [524] parent: 8 [524] parent: 9 [524] parent: 10 [524] parent: 11 [524] parent: 12 [524] parent: 13 [524] parent: 14 [524] parent: 15 [524] parent: 16 [524] parent: 17 [524] parent: 18 [524] parent: 19 [524] parent: 20 [524] parent: 21 [524] parent: 22 [524] parent: 23 [524] parent: 24 [524] parent: 25 [524] parent: 26 [524] parent: 27 [524] parent: 28 [524] parent: 29 [524] parent: 30 [524] parent: 31 [524] parent: 32 [524] parent: 33 [524] parent: 34 [524] parent: 35 [524] parent: 36 [524] parent: 37 [524] parent: 38 [524] parent: 39 [524] parent: 40 [524] parent: 41 [524] parent: 42 [524] parent: 43 [524] parent: 44 [524] parent: 45 [524] parent: 46 [524] parent: 47 [524] parent: 48 [524] parent: 49 [524] parent: 50 [524] parent: 51 [524] parent: 52 [524] parent: 53 [524] parent: 54 Hello World[525] child [524] parent: 55 [525] child: 0 [524] parent: 56 [525] child: -1 [524] parent: 57 [525] child: -2 [524] parent: 58 [525] child: -3 [524] parent: 59 [525] child: -4 [524] parent: 60 [525] child: -5 [524] parent: 61 [525] child: -6 [524] parent: 62 [525] child: -7 [524] parent: 63 [525] child: -8 [524] parent: 64 [525] child: -9 [524] parent: 65 [525] child: -10 [524] parent: 66 [525] child: -11 [524] parent: 67 [525] child: -12 [524] parent: 68 [525] child: -13 [524] parent: 69 [525] child: -14 [524] parent: 70 [525] child: -15 [524] parent: 71 [525] child: -16 [524] parent: 72 [525] child: -17 [524] parent: 73 [525] child: -18 [524] parent: 74 [525] child: -19 [524] parent: 75 [525] child: -20 [524] parent: 76 [525] child: -21 [524] parent: 77 [525] child: -22 [524] parent: 78 [525] child: -23 [524] parent: 79 [525] child: -24 [524] parent: 80 [525] child: -25 [524] parent: 81 [525] child: -26 [524] parent: 82 [525] child: -27 [524] parent: 83 [525] child: -28 [524] parent: 84 [525] child: -29 [524] parent: 85 [525] child: -30 [524] parent: 86 [525] child: -31 [524] parent: 87 [525] child: -32 [524] parent: 88 [525] child: -33 [524] parent: 89 [525] child: -34 [524] parent: 90 [525] child: -35 [524] parent: 91 [525] child: -36 [524] parent: 92 [525] child: -37 [524] parent: 93 [525] child: -38 [524] parent: 94 [525] child: -39 [524] parent: 95 [525] child: -40 [524] parent: 96 [525] child: -41 [524] parent: 97 [524] parent: 98 [524] parent: 99 [525] child: -42 [525] child: -43 [525] child: -44 [525] child: -45 [525] child: -46 [525] child: -47 [525] child: -48 [525] child: -49 [525] child: -50 [525] child: -51 [525] child: -52 [525] child: -53 [525] child: -54 [525] child: -55 [525] child: -56 [525] child: -57 [525] child: -58 [525] child: -59 [525] child: -60 [525] child: -61 [525] child: -62 [525] child: -63 [525] child: -64 [525] child: -65 [525] child: -66 [525] child: -67 [525] child: -68 [525] child: -69 [525] child: -70 [525] child: -71 [525] child: -72 [525] child: -73 [525] child: -74 [525] child: -75 [525] child: -76 [525] child: -77 [525] child: -78 [525] child: -79 [525] child: -80 [525] child: -81 [525] child: -82 [525] child: -83 [525] child: -84 [525] child: -85 [525] child: -86 [525] child: -87 [525] child: -88 [525] child: -89 [525] child: -90 [525] child: -91 [525] child: -92 [525] child: -93 [525] child: -94 [525] child: -95 [525] child: -96 [525] child: -97 [525] child: -98 [525] child: -99

18. 19 P ro ce ss Te rm i n ati on Cond iti ons w hi c h te r mi nat e pro ce ss e s N or m a l e xit (volunt a ry) Error e xit (volunt a ry) F a t a l e rror (involunt a ry) K ill e d by a noth e r pro ce ss (involunt a ry)

19. 3 types of Kernel Mode Transfer Syscall Process requests a system service, e.g., exit Like a function call, but “outside” the process Does not have the address of the system function to call Like a Remote Procedure C all (RPC) – for later Marshall the syscall ID and arguments in registers and execute syscall Interrupt External asynchronous event triggers context switch e g . Timer, I/O device Independent of user process Trap or Exception Internal synchronous event in process triggers context switch e .g., Protection violation (segmentation fault), Divide by zero, …

20. Recall: User/Kernel (Privileged) Mode User Mode Kernel Mode Full HW access Limited HW access exec syscall exit rtn interrupt rfi exception

21. I nt e rrupt s Forcibly change normal flow of control Enters the kernel at a specific point; the kernel then figures out which interrupt handler should run Many different types of interrupts

22. T y p es o f I nt e rrupt s Sy nchronous v ersus asynchronous Asy nchronous F ro m e xte r na l sourc e , su ch as I/O d e v i ce N ot re l ate d to i nst r uct i o n be i n g e x ecute d Sy nchronous (a l so ca ll e d e xcept i on s ) Pro g r a mm i n g errors or requests f or k e r ne l i nte r v ent i o n F au l ts — correcta b l e; of f end i n g i nst r uct i o n i s ret r i e d T r aps — ofte n f or de b ugg i ng; i nst r uct i o n i sn ’t ret r i e d

23. / p r o c/i nt e rrupt s $ ca t /proc/interrupt s CPU C olu m ns: IR Q , count, in ter r upt contr olle r , d e v i ces : 13006660 9 XT-PI C time r 2 : XT-PI C cascad e 3 : XT-PI C uhci_hc d 5 : XT-PI C uhci_hc d 8 : 43 6 XT-PI C rt c 9 : 243156 8 XT-PI C acpi , libata , uhci_hcd , et h 10 : XT-PI C ehci_hcd , uhci_hc d 14 : 117024 XT-PI C ide NMI : ERR :

24. Int e rrupt hand li ng ( a ) (b) S t e ps i n s t a rti ng a n I/ O d e vi c e a nd g e tti ng int e rrupt How the CPU i s int e rrupt e d 25

25. Int e rrupt hand li ng (2) S k e l e t on of w h a t l ow e s t l e v e l of OS do e s w h e n a n in te rrupt o cc urs 26

26. Interrupt Controller Interrupts invoked with interrupt lines from devices Interrupt controller chooses interrupt request to honor Mask enables/disables interrupts Priority encoder picks highest enabled interrupt Software Interrupt Set/Cleared by Software Interrupt identity specified with ID line CPU can disable all interrupts with internal flag Non- M askable I nterrupt line (NMI) can’t be disabled Network IntID Interrupt Interrupt Mask Control Software Interrupt NMI CPU Priority Encoder Timer Int Disable

27. Sys t em Calls Syste m ca ll s are th e w a y i n w h i ch user pro g r a ms request act i o ns fro m th e k e r ne l A l m ost a l w a y s , th e y represent contro ll e d access to p r i v il e ge d ope r at i ons If so m eth i n g ca n b e don e w i th reasona b l e effic i ency pure l y at user l e v e l , i t shou l d not b e a syste m ca l l Th e k e r ne l i s entere d v i a a soft w are i nter r upt

28. A d d i n g a Sys t em Call W r i te th e cod e Download\Extract the kernel source R out i nes are gene r a ll y na m e d sy s xxx To define a new system call sys_hello (), Create a directory hello in the kernel source directory( / usr / src /linux-3.16/) If i t ’ s i n a n e w fi l e , ad d th e fi l ena me to th e approp r i ate M a k e fi l e Add the new system call ( sys_hello () ) into the system call table (syscall_32.tbl file A d d th e sysca l l n u m ber to li n ux/sysca ll s .h W r i te th e C li nkag e rout i n e

29. A Rei mp le m e nt a t i o n o f getpid() #includ e <asm/unistd.h > asmlinkag e lon g sys_mypid(void ) { retur n current->tgid ; } “ asmlinkage ” is a key word used to indicate that all parameters of the  function would be available on the stack. #include < linux / kernel.h >   asmlinkage long sys_hello (void) {         printk (“Hello world\n”);         return 0;  }

30. Si mp le User L i n k a g e #defin e NR_mypi d 29 4 syscall0(long , mypid ) in t main( ) { printf("%d\n" , mypid()) ; retur n ; } syscall i s f or a syste m c all w i th n o argu m ents; there are al so syscall 1 , syscall 2 , . . . , syscall 6 #include < stdio.h > #include < linux / kernel.h > #include <sys/ syscall.h > #include < unistd.h > int main() {          long int amma = syscall (354);           printf (“System call sys_hello returned %ld\n”, amma );          return   0; }

31. #include < stdio.h > # include < pthread.h > /* thread function definition*/ void * threadFunction ( void * args ) { while (1 ) { printf ("I am threadFunction .\n"); } } int main() { /* creating thread id*/ pthread_t id ; int ret ; /* creating thread*/ ret = pthread_create (& id ,NULL,& threadFunction ,NULL ); if (ret ==0){ printf ("Thread created successfully.\n"); } else { printf ("Thread not created.\n"); return 0; /*return from main*/ } while (1 ) { printf ("I am main function.\n"); } return 0; }

32. If file name is  main.c  while output file name is main To compile $ gcc main.c -o main - lpthread To run $ ./main

33. Thread created successfully. I am threadFunction . I am threadFunction . I am threadFunction . I am threadFunction . … … I am threadFunction . I am main function. I am main function. I am main function. I am main function. … … I am main function. I am threadFunction . … and so on.