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SubjectRe: [patch 2/3] rtmutex: Propagate priority settings into PI lock chains


On Thu, 22 Jun 2006, Esben Nielsen wrote:

> > The above means that you cant ever call sched_setscheduler from a
> > interrupt handler (or softirq). The rt_mutex_adjust_prio_chain since that
> > grabs wait_lock which is not for interrupt use.
>
> Worse in RT context: It makes it unhealthy to call from a RT task as it
> doesn't have predictable runtime unless you know that the target task is
> not blocked on a deep locking tree.
>
> I know this is very unlikely to happen very often in real life and this
> thread isn't about preempt-realtime, but I'll say it anyway: Hard realtime

Esben, you are right. This is not about RT so it does _not_ belong in this
thread. Please keep the topic in this thread about -mm. We already have
a RT thread to discuss this in.

My comments here where about a fact that setscheduler when from interrupt
context friendly to interrupt context unfriendly and I thought it would
be good to document that fact. I like Andrews answer better. Document it
with a BUG_ON(in_interrupt).

-- Steve

> is about avoiding surprisingly long execution times - especially those
> which are extremely unlikely to happen, but nevertheless are possible,
> because you are not very likely to see those situations in any tests, and
> therefore you can suddenly miss deadlines in the field without a clue what
> is happening.
>
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