theory of process management

This is more of a theoretical question, and I'm stuggling to find anything that mentions it outside my lecture notes.

In a the 3 state process model for process management, you have 3 states, running, blocked and ready. So my question is when can a state transition of blocked to running occur, without the process first passing through the ready queue?

Thanks 开发者_如何转开发hope it makes sense :)

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I'm not sure what, if any, specific domain you are asking about. However, I can translate this to a general manufacturing domain, based on concepts learned through APICS CPIM certification.

If you think of a production line, it may have one of three states:

• RUNNING: Product is being produced and the line and its dependencies are operational.
• BLOCKED: Product is not coming off the line because something (ie, a machine down) is blocking output.
• READY: The line is operational, but product is not coming off the line because there is no product to be produced.

Let's imagine now that a line is RUNNING. Product is flowing from the start of the line to the end of the line. Let's now say that a machine on that line breaks down. The line is now BLOCKED, however there is still product on the line, some of which is probably not finished. As soon as that machine comes back on or gets replaced, the line immediately goes to RUNNING (and not READY) as there is already product in place and in queue. Now, if while the machine was down, the product on the line was removed, then when the machine came back online, the line as a unit would be READY.

It may also be worth noting that APICS actually defines 5 states for production. They are QUEUE, SETUP, RUN, WAIT, MOVE.