help2002

It's UWAweek 30 (2nd semester, week 1)

help2002

This forum is provided to promote discussion amongst students enrolled in CITS2002 Systems Programming.
Please consider offering answers and suggestions to help other students! And if you fix a problem by following a suggestion here, it would be great if other interested students could see a short "Great, fixed it!" followup message.

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UWA week 35 (2nd semester, week 6) ↓

RUNNING state (all 4)

4:29am Tue 29th Aug, Christopher M.

ANONYMOUS wrote:

> Hmm ok, but my question is that, while something is transitioning out from the running state, in that time can something else from the ready queue swoop in and start running? > > I'm guessing not as the CPU is busy doing the transition but i would just like to double check. Moreover if only one transition can occur at a time, what do we do when multiple things need to change state, for example one thing from BLOCKED to READY and something else from RUNNING to BLOCKED.

There's a single CPU, and it can be used by either users' executing processes, or the OS (performing state transitions). Before the CPU can be used by the OS, or at the very beginning of the OS's actions, the executing user process's information/state must be saved somewhere. We can't just assume that its details are (somehow) immediately available once the OS has finished performing a state transition.