self doubt in OS(galvin)

Question

All safe states are deadlock free. But we can go to deadlock with some combination of sequence? So if the question is, from the safe state can we enter deadlock? Ans should be YES.

please give your thought

Comments

https://gateoverflow.in/138117/deadlock

Answer 1

We cannot enter into deadlock from a safe state. In second line  you have asked can we go to deadlock with some combination of sequence? Ans is maybe, because if there exists no safe sequence it is in unsafe state. However an unsafe state may or may not be lead to deadlock. But There is no chance of getting into deadlock from a safe state.

Comments

thanks bro for answering,

although i have already read all the references.

i know in practically neither system can go to unsafe state from safe state, nor go to deadlock from unsafe state.

But if we satisfy some request randomly in safe state which may lead to us in unsafe state. And from unsafe state we may or may not lead to deadlock.

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It is called Safe state because of the Safe sequence, now if we don't want to follow that sequence then it will not be called safe state.

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Does'nt bankers algorithm  comes into play here??

Answer 2

safe state current allocation result no problem as cpu has enough resources

but in case of unsafe state current allocation may result in low available resource and from that unsafe state we can reach to a deadlock

Answer 3

Dead lock Is a subset of Unsafe State , it means that If the System is in Deadlock It will necessary In the Unsafe state but it does not mean that if system is in unsafe state then it is definitely deadlock state.

(or)

All safe states are deadlock free. But not all unsafe states lead to deadlock. There might be a possibility that an unsafe state might complete successfully. Unsafe states are a necessary condition for deadlock, but not sufficient.