Re: [patch 04/10] PI-futex: scheduler support for PI

[Ingo Molnar <mingo@elte.hu>]

* Andrew Morton <akpm@osdl.org> wrote:

> > +#ifdef CONFIG_RT_MUTEXES
> > +
> > +/*
> > + * rt_mutex_setprio - set the current priority of a task
> > + * @p: task
> > + * @prio: prio value (kernel-internal form)
> > + *
> > + * This function changes the 'effective' priority of a task. It does
> > + * not touch ->normal_prio like __setscheduler().
> > + *
> > + * Used by the rt_mutex code to implement priority inheritance logic.
> > + */
> > +void rt_mutex_setprio(task_t *p, int prio)
> > +{
> 
> This function is not really rt-mutex-related at all, is it?  It's just 
> a piece of new scheduler functionality which various things might use.

well, this particular function should only be used by the rt-mutex 
subsystem, because it sets the priority of a task unconditionally.  
Priority will vary depending on how other tasks block on a lock held by 
this task. So if some other subsystem changes the priority via this 
interface, it will both interfere with PI, and PI will interfere with 
this.

	Ingo
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