Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756242Ab0DUT5T (ORCPT ); Wed, 21 Apr 2010 15:57:19 -0400 Received: from casper.infradead.org ([85.118.1.10]:60416 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753908Ab0DUT5S (ORCPT ); Wed, 21 Apr 2010 15:57:18 -0400 Subject: Re: Considerations on sched APIs under RT patch From: Peter Zijlstra To: Primiano Tucci Cc: rostedt@goodmis.org, linux-kernel@vger.kernel.org, tglx In-Reply-To: References: <1271755208.1676.422.camel@laptop> <1271804453.10448.168.camel@gandalf.stny.rr.com> <1271839772.1776.58.camel@laptop> <1271854016.10448.172.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 21 Apr 2010 21:57:13 +0200 Message-ID: <1271879833.1776.186.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 978 Lines: 22 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/