Question

When ever a process is going running to blocked state its get pre-empted right ??

so this is also a preemptive scheduling  ??

Answer 1

Process moved to blocked state does not imply that it is preempted. Preemption is when a process is moved back to the Ready Queue from the Running State against its will.

Answer 2

Nopes. Pre-emption is if a process changes state from Running to Ready- that is it has a live CPU burst and during this time itself CPU is taken away from it. All CPU scheduling algorithms work on CPU bursts- not the execution time of a process.

Comments

@Pranay How come critical section come here?

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Our assumption is that at a time only a single process can execute. (like in mutual exclusion only one process can execute in critical section )

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Okay. You meant accessing "CPU" as a CS- which is not correct even though CPU can be used only by 1 process at a time.

Now, when a process goes to blocked state, it no longer needs CPU- it by itself relinquishes CPU- no need of preemption - it is "finishing" its CPU burst here.

Answer 3

Among all the 5 state through which a process goes , BLOCK state is the only state where the process goes by its will .while in other it depends upon the Scheduler .. And The scheduler we have seen are care about CPU bound process , and not for I/o bound process . So here the i/o process leave the cpu by its will . And in premptive CPu throws the process out and take another process (Note the diff between between former and latter case ) hence its is non premptive

Answer 4

Not necessarily,

process moving to block state implies that process is waiting for some resource or we can say that process is doing I/O.

preemption means that a process is in a running state and we forcefully preempted the process and then the process is kept in ready queue. instead of having all the means available for process execution, the process is half way stopped.