Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932399AbZKRVEz (ORCPT ); Wed, 18 Nov 2009 16:04:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932287AbZKRVEy (ORCPT ); Wed, 18 Nov 2009 16:04:54 -0500 Received: from mail-fx0-f221.google.com ([209.85.220.221]:55101 "EHLO mail-fx0-f221.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932269AbZKRVEx (ORCPT ); Wed, 18 Nov 2009 16:04:53 -0500 Subject: Re: [PATCH] cleanup sched_yield (sys)call nesting. From: Sven-Thorsten Dietrich To: Thomas Gleixner Cc: Jean Delvare , Leon Woestenberg , Alan Cox , Mark Brown , linux-i2c@vger.kernel.org, rt-users , "Ben Dooks (embedded platforms)" , Peter Zijlstra , LKML In-Reply-To: References: <20091107210147.3e754278@hyperion.delvare> <4AF7148C.9090706@thebigcorporation.com> <20091112211255.09cd884a@hyperion.delvare> <20091116155606.GC29479@sirena.org.uk> <20091118010520.4cd397d4@lxorguk.ukuu.org.uk> <20091118175202.490989d8@hyperion.delvare> <1258577194.12429.86.camel@sven.thebigcorporation.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 18 Nov 2009 13:04:50 -0800 Message-Id: <1258578290.12429.108.camel@sven.thebigcorporation.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1841 Lines: 42 On Wed, 2009-11-18 at 21:56 +0100, Thomas Gleixner wrote: > On Wed, 18 Nov 2009, Sven-Thorsten Dietrich wrote: > > On Wed, 2009-11-18 at 17:52 +0100, Jean Delvare wrote: > > > On Wed, 18 Nov 2009 17:28:53 +0100, Leon Woestenberg wrote: > > > > On Wed, Nov 18, 2009 at 2:05 AM, Alan Cox wrote: > > > > > Our timers are very efficient and some day we will need to make jiffies a > > > > > function and stop the timer ticking for best performance. At that point > > > > > timers are probably the most efficient way to do much of this. > > > > > > > > The problem with I2C bitbanged is the stringent timing, we need a way > > > > to have fine-grained sleeping > > > > mixed with real-time tasks in order to make this work. > > > > > > FWIW, the problem that was initially reported has nothing to do with > > > this. i2c-algo-bit used mdelay() during transactions, not yield(). > > > yield() is used only in once place, _between_ transactions attempts. > > > There are no strict timing constraints there. > > > > > > > I agree that dropping out sched_yield entirely should maybe start by > > deprecating / flagging as a warning in sched_rt.c. > > Errm, that's unrelated to sched_rt.c. > > yield() in the kernel in general is needs to be deprecated. > > > This is just a minimal cleanup I stumbled across while looking at it - > > to get away from the uglyness of calling into the syscall interface from > > inside the Kernel. > > And why exactly is that ugly ? Calling from a function returning void into a non-void function and then ignoring the return code ? -- 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/