preemptive kernels and the use of smp_processor_id()

[Valdis.Kletnieks at vt.edu]

On Wed, 24 Jul 2013 18:52:40 -0000, Rajat Jain said:

> I though preemptible only means that a process can only be preempted (not
> moved to another core) under following situations:

> 1) An interrupt happens (In case of timer, it could put the process back in queue if its time slice expired).

Actually, in case of any interrupt, be it timer or I/O or NMI or whatever.

> 2) The process goes to sleep (can be a result of a call that can sleep).

And there's no actual guarantee that when the process gets rescheduled, that
you'll return to the same core you were on.

> Can some one shed light on what conditions would a running process be moved to another core?

Pretty much anytime the scheduler comes to that decision. :)
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