Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752557AbZKSNFc (ORCPT ); Thu, 19 Nov 2009 08:05:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752052AbZKSNFc (ORCPT ); Thu, 19 Nov 2009 08:05:32 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:60757 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751698AbZKSNFa convert rfc822-to-8bit (ORCPT ); Thu, 19 Nov 2009 08:05:30 -0500 Subject: Re: yield() in i2c non-happy paths hits BUG under -rt patch From: Peter Zijlstra To: Alan Cox Cc: Jean Delvare , Thomas Gleixner , Leon Woestenberg , Mark Brown , Sven-Thorsten Dietrich , linux-i2c@vger.kernel.org, rt-users , "Ben Dooks (embedded platforms)" , LKML In-Reply-To: <20091119125906.6ad00edd@lxorguk.ukuu.org.uk> 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> <20091119130526.23a69b85@hyperion.delvare> <20091119125906.6ad00edd@lxorguk.ukuu.org.uk> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 19 Nov 2009 14:06:54 +0100 Message-ID: <1258636014.4372.328.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 872 Lines: 26 On Thu, 2009-11-19 at 12:59 +0000, Alan Cox wrote: > > Well, I guess only people monitoring system latency would notice, as > > this is the only thing yield() was supposed to help with in the first > > place. > > if (need_resched()) > schedule(); aka. cond_resched(); > will make non-rt tasks act politely at the right moments. RT tasks will > likely immediately get to take the CPU again depending upon the > scheduling parameters in use. Right, FIFO will simply NOP it, since if it was the highest running task, it will still be. RR could possibly run out of its slice and schedule to another RR of the same prio. -- 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/