Select the sequence of events that are NOT possible, assuming a non-interruptible kernel code
(Note: non-interruptible kernel code means, if the kernel code is executing, then interrupts will be disabled).
Note: A possible sequence may have some missing steps in between. An impossible sequence will will have n and n+1th steps such that n+1th step can not follow n'th step.

Question

Select the sequence of events that are NOT possible, assuming a non-interruptible kernel code 
 (Note: non-interruptible kernel code means, if the kernel code is executing, then interrupts will be disabled). 
 Note: A possible sequence may have some missing steps in between. An impossible sequence will will have n and n+1th steps such that n+1th step can not follow n'th step.

Answer

P1 running 
 P1 makes sytem call and blocks 
 Scheduler 
 P2 running 
 P2 makes sytem call and blocks 
 Scheduler 
 P1 running again

Answer

P1 running  
 P1 makes system call 
 system call returns 
 P1 running 
 timer interrupt 
 Scheduler running 
 P2 running

Answer

P1 running 
 P1 makes sytem call and blocks 
 Scheduler 
 P2 running 
 P2 makes sytem call and blocks 
 Scheduler 
 P3 running 
 Hardware interrupt 
 Interrupt unblocks P1 
 Interrupt returns 
 P3 running 
 Timer interrupt 
 Scheduler 
 P1 running

Answer

P1 running 
 P1 makes sytem call 
 Scheduler 
 P2 running 
 P2 makes sytem call and blocks 
 Scheduler 
 P1 running again

Answer

P1 running 
 P1 makes system call 
 timer interrupt 
 Scheduler 
 P2 running 
 timer interrupt 
 Scheuler 
 P1 running 
 P1's system call return

Answer

P1 running 
 keyboard hardware interrupt 
 keyboard interrupt handler running 
 interrupt handler returns 
 P1 running 
 P1 makes sytem call  
 system call returns 
 P1 running 
 timer interrupt 
 scheduler 
 P2 running

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Select the sequence of events that are NOT possible, assuming a non-interruptibl...

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