From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755115AbXGaJVd (ORCPT ); Tue, 31 Jul 2007 05:21:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753931AbXGaJVZ (ORCPT ); Tue, 31 Jul 2007 05:21:25 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:34263 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753284AbXGaJVY (ORCPT ); Tue, 31 Jul 2007 05:21:24 -0400 Date: Tue, 31 Jul 2007 11:21:19 +0200 From: Ingo Molnar To: Gregory Haskins Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] RT: Preemptible Function-Call-IPI Support Message-ID: <20070731092119.GA15968@elte.hu> References: <20070730211350.5162.99143.stgit@novell1.haskins.net> <20070730211539.5162.87483.stgit@novell1.haskins.net> <20070731091903.GA15822@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070731091903.GA15822@elte.hu> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org [ mail re-sent with lkml Cc:-ed. _Please_ Cc: all patches to lkml too! Unless you want -rt to suffer the fate of -ck, keep upstream involved all the time. The recent /proc/interrupts-all discussion with upstream folks showed the clear benefits of that approach. ] * Gregory Haskins wrote: > This code allows FUNCTION_CALL IPIs to become preemptible by executing > them in kthread context instead of interrupt context. They are > referred to as "Virtual Function Call IPIs" (VFCIPI) because we no > longer rely on the actual FCIPI facility. Instead we schedule a > thread to run. This essentially replaces the synchronous FCIPI with > an async RESCHEDULE IPI. why do we need this? It's quite complex and brings little extra AFAICS. See the "schedule_on_each_cpu-enhance.patch" from Peter Ziljstra that lets a function to be executed on all CPUs. That should be extended (trivially) to execute a function on another CPU. That's all we need. Ingo