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KILL A PROCESS

KILL A PROCESS. AFTER LAST END, CTRL – C etc ex: PR WITH PID = 3 TERMINATES PID = 3 – GIVEN TO SYSTEM CALL SYSTEM CALL CAUSES SOFTWARE INT & OS ROUTINE STARTS EXCUTING. NO USER PR. IS IN RUNG ST AT THIS JUNCTURE. 3. OS STORES PID = 3

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KILL A PROCESS

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  1. KILL A PROCESS AFTER LAST END, CTRL – C etc ex: PR WITH PID = 3 TERMINATES PID = 3 – GIVEN TO SYSTEM CALL SYSTEM CALL CAUSES SOFTWARE INT & OS ROUTINE STARTS EXCUTING. NO USER PR. IS IN RUNG ST AT THIS JUNCTURE

  2. 3. OS STORES PID = 3 4. OS ACCESSES PCB WITH PID = 3. FREES RESOURCES & MEM WITH HELP OF IM & MM 5. OPEN FILES OF PCB 3 CLOSED

  3. 6. OS ADDS PCB 3 TO LIST OF FREE PCBs AT THE END 7. PCB CHAINS UPDATED – ILUSTRN ALL CHILD PRS OF PARENT PR. 8 MASTER LIST OF ALL PRS – UPDATED.

  4. MASTER LIST OF ALL PRs

  5. DISPATCH A PROCESS • CURRENTLY RUNG PR GETS OVER ( SAY PR. WITH PID = 3) & THERE IS A NEED TO DISPATCH A NEW PR. • OS ACCESSES READY HEADER – HEAD OF THE CHAIN – PCB WITH PID = 8 • REMOVES PCB 8 FROM RDY LIST & UPDATES READY H. – FIG. • OS UPDATES RNG H. TO PID = 8

  6. OS LOADS ALL CPU REGS WITH REG VALS STORED IN REG SAVE AREA OF PCB 8 • PR. WITH PID = 8 STARTS EXECG WHERE IT HAD LEFT EARLIER – OR JUST STARTED • MASTER LIST OF KNOWN PRS. – UPDATED

  7. CHANGE PRIORITY OF A PR. • OS IS SUPPLIED WITH PID & NEW PRIORITY PARAMETERS. • OS ACCESSES PCB FOR THE PID • IF ALG IS BASED ON PRIORITIES THEN RDY LIST & CORRESP HEADERS UPDATED.

  8. BLOCK A PR ASSUME – RNG PR. WITH PID = 8 ISSUES A SYSTEM CALL TO READ A RECORD ( DISK) – THIS WILL HAVE TO BE BLOCKED BY A SYSTEM CALL. • ALL CPU REGS etc – SAVED – SAVE AREA OF PCB WITH PID = 8 • STATUS – PID = 8 – UPDATED TO BL. • PCB 8 – ADDED TO BL LIST (END)

  9. SCHEDULER PR. WITHIN OS IS EXECUTING AT THIS JUNCTURE. FIG 5.20

  10. TIME UP A PR. TIMER INT IS GENR.. FOR THE TIME UP PR.. OS EXEC SYSTEM CALL : PR. TIME UP Ex: TIME UP FOR PR.. – PID = 13 • OS SAVES – • OS UPDATES STATUS OF THAT PCB TO RDY ( NOT BLOCKED) • PR. WITH PID = 13 LINKED TO CHAIN OF RDY PRS.. – UPDATED

  11. RNG.. H – UPDATED – SCHED PR. IS EXELG.. • MASTER LIST UPDATED • FIG 5.22

  12. WAKE UP A PR.. WHEN INPUT FOR A PR IS COMPLETED BY HARDWARE – BEFORE WAKE UP SYSTEM CALL FOLLOWING TAKES PLACE: • HARDWARE GENRS.. INT • ISR IS IDENTIFIED & EXEC. • ISR ACCESSES DCB ( DEVICE CONTR. BLOCK) FOR THAT DEV IN IM MODULE- GETS PR. ID

  13. ISR EXEC WAKE UP SYSTEM CALL FOR THAT PR. • ASSUME I/O IS COMPLETED ON BEHALF OF PR. WITH PID = 2 – NEEDS TO BE WOKEN UP • OS CHANGES STATUS – PID = 2 – RDY • REMOVES – PID = 2 FROM BL LIST & UPDATES BL H

  14. CHAINS PR. – PID = 2 IN LIST OF RDY PRS. UPDATES RDY H • UPDATES MASTER LIST • FIG 5.23

  15. SUSPEND / RESUME OPERN.

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