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+12 votes

When an interrupt occurs, an operating system

  1. ignores the interrupt

  2. always changes state of interrupted process after processing the interrupt

  3. always resumes execution of interrupted process after processing the interrupt

  4. may change state of interrupted process to ‘blocked’ and schedule another process.


asked in Operating System by Veteran (66.1k points) 1148 2197 2522 | 1.8k views
@Arjun sir, please answer this

6 Answers

+17 votes
Best answer
Think about this:
When a process is running and after time slot is over, who schedules new process?
- Scheduler.

But to run "scheduler" itself, we have to first schedule scheduler.
This is catch here, We need hardware support to schedule scheduler. That is hardware timer. When timer expires, then hardware generates interrupt and scheduler gets schedule.
Now after servicing that interrupt, schedular may schedule another process.

This was about Hardware interrupt.

Now think if user invokes a system call, System call in effect leads to interrupt, and after this interrupt CPU resumes execution of current running process,

Conclusion: Its about type of interrupt being serviced.
Options with "always" are false.

Hence option D.
answered by Veteran (11.9k points) 38 103 230
selected by
+15 votes
A. Depends on the priority.
B. Not always.
C. Not always. If some high priority interrupt comes during execution of current interrupt, then?
D. Seems to be correct.
answered by Boss (8.7k points) 14 35 91

For C choice, it is like interrupt is taken and what it does after finishing interrupt handler. No need to worry about priority here.

D seems the most appropriate though..
I can not understand option b and c

Plzzzz provide correct explanation
C) , can be like - what if a higher priority process comes , after servicing of interrupt.
If you see process state diagram in os an process can be in blocked state only if it is waiting for an I/O or event so D is not appropriate
+2 votes
Whether the interrupted process will complete execution or some other process would execute is decided by the process scheduler.

For instance if the interrupt signaled an IO completion event,that caused a high priority process to transition from blocked to ready state, the OS might preempt the interrupted process and dispatch the high priority process.
Hence answer is D.

Source: Harvey M. Deitel
answered by Junior (625 points) 2 5 12
–2 votes

I think C is most appropriate , because There is a flag called IEN  ( Interrupt enable ) Flag which is set to 1 when an interrupt arrives .

but as soon as you serviced the interrupt , and when the  contents of interrupted process are restored till that time IEN is disabled so that no other interrupts can arrived or set the IEN flag . 

As soon as the restoring is done , interrupted process is executed and then ( IEN  is enabled ) so  it may happen that happen that another higher priority interrupt . But if you see there may be small time  but it is always case that interrupted process will be excuted ( may be for very short time if higher ones come ).


answered by Active (2.1k points) 12 51 73
edited by
–2 votes
A ) Yes it is possible and such interrupt are know as maskable interrupt

B ) Yes (may not do it immediately but may be after some point of time) servicing interrupt process will executed the interrupted process (from ready to running)

C ) similar reason as B

D ) Not possible because an process can be blocked only if it is waiting for I/O else it has to go to ready state
answered by Boss (9.4k points) 4 29 58
–3 votes
ans is  c
answered by Loyal (3.6k points) 7 35 55
why ?

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