linux-kernel - Re: Considerations on sched APIs under RT patch

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Message-ID: <1271879833.1776.186.camel@laptop>
Date:	Wed, 21 Apr 2010 21:57:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Primiano Tucci <p.tucci@...il.com>
Cc:	rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	tglx <tglx@...utronix.de>
Subject: Re: Considerations on sched APIs under RT patch

On Wed, 2010-04-21 at 21:24 +0200, Primiano Tucci wrote:
> Is it sure that calling a scheduler api won't induce a re-scheduling
> of the caller process (e.g. as in the case of a lock held by another
> processor)? It would be very unpleasant if the scheduling apis can
> induce re-scheduling, making the realization of a Real Time scheduling
> infrastructure completely un-deterministic. 

No, any syscall can end up blocking/scheduling there are no exceptions.
But blocking doesn't mean its non-deterministic, esp. when coupled with
things like PI.

But you do have to treat system resources as such, that is they can (and
will) create cross-cpu dependencies, if you do not take that into
account you will of course be surprised.



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