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SubjectRe: [RFC PATCH 0/6] Convert all tasklets to workqueues

* Daniel Walker <dwalker@mvista.com> wrote:

> > - tasklets have certain fairness limitations. (they are executed in
> > softirq context and thus preempt everything, even if there is
> > some potentially more important, high-priority task waiting to be
> > executed.)
>
> Since -rt has been executing tasklets in process context for a long
> time, I'm not sure this change would cause to many regressions.
> However, it seems like implicit dependencies on "tasklets preempt
> everything" might crop up. The other issue is if they don't "preempt
> everything" (most of the time), what default priority do we give them
> (all of the time)? [...]

there is no such guarantee at all (of 'instant preemption'), even with
current, softirq-based tasklets. A tasklet might be 'stolen' by another
CPU. It might be delayed to the next timer tick (or other softirq
execution). Or it might be delayed into a ksoftirqd context, which
currently runs at nice +19. So your worry of implicit execution
dependencies is unfounded, because, if they existed, they would be bad
(and triggerable) bugs today too.

Ingo
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