From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stanislav Meduna Subject: Re: RT_PREEMPT autodetection from user program Date: Sun, 20 Jan 2013 10:49:28 +0100 Message-ID: <50FBBDA8.5060605@meduna.org> References: <97041258-E312-4163-96B2-9077EED68E0B@mah.priv.at> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: linux-rt-users@vger.kernel.org Return-path: Received: from www.meduna.org ([92.240.244.38]:42341 "EHLO meduna.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751140Ab3ATKDL (ORCPT ); Sun, 20 Jan 2013 05:03:11 -0500 Received: from dial-95-105-165-4-orange.orange.sk ([95.105.165.4] helo=[192.168.130.22]) by meduna.org with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1TwrWu-0002uQ-Ko for linux-rt-users@vger.kernel.org; Sun, 20 Jan 2013 10:49:34 +0100 In-Reply-To: <97041258-E312-4163-96B2-9077EED68E0B@mah.priv.at> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 20.01.2013 01:13, John Morris wrote: > LCNC drives machines that weigh many tons and spins > spindles at 24k RPM, so this is important! ... > We haven't found /proc/config.gz in any vendor-provided > PREEMPT_RT kernels, so that is not an option either. On 20.01.2013 01:49, Michael Haberler wrote: > A false positive on a vanilla kernel could be a safety hazard. If we are speaking safety here I'd say that you have to support specific version of kernel on specific hardware that _you_ have quality assured. Anything else is a recipe for problems. I've seen OSADL Linux deadlock, RT PREEMPT leaking memory, RT PREEMPT on but without high-res timers, IDE driver monopolizing processor so that the RT throttler was activated, priority inversion issues between kernel and application threads, interrupt latencies due to interrupt routing on the specific hardware etc. There is no way you can guarantee anything if you are using vendor-provided kernel on a hardware you have never seen. With your kernel, a list of supported hardware, with initscripts that are checking if the environment matches and with the help from this list (thank you guys, the level of support here is excellent!) you will sleep a lot better. Just my two cents Regards -- Stano