On Friday 18 October 2002 04:56 am, Momchil Velikov wrote:
> >>>>> "Sonawane" == Sonawane, Rahul (Rahul) <sonawane@avaya.com> writes:
>
> Sonawane> Let me ask the other way. If a real-time process(SHED_FIFO)
> Sonawane> is running and it needs some IO to be done ,in that case
> Sonawane> will it go in the wait queue or it will just continue
> Sonawane> executing till it finishes without giving other processes
> Sonawane> any chance. Thanks for your response, Rahul
This switch statment in schedule() removes any process from the run queue
that is in a state that is not TASK_RUNNING. (i.e blocking for I/O)
586 switch (prev->state) {
587 case TASK_INTERRUPTIBLE:
588 if (signal_pending(prev)) {
589 prev->state = TASK_RUNNING;
590 break;
591 }
592 default:
593 del_from_runqueue(prev);
594 case TASK_RUNNING:;
595 }
>
> Depends, but in general the thread, which performs I/O will block,
> waiting for the I/O to finish, thus allowing other threads to
> run. Sometimes (with PIO) it is possible for the thread to to all the
> work itself, without blocking. While being incredibly stupid,
> nevertheless there may exist drivers written that way or devices,
> which do not allow other implementation (e.g. have no interrupts). In
> that case no other thread will run.
>
> ~velco
>
> PS. For the second case, one may create a dedicated driver thread in
> order to compensate for the lack of parallellism in the device and
> allow the original real-time thread to block.
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