Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161133AbXBGKQ6 (ORCPT ); Wed, 7 Feb 2007 05:16:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161130AbXBGKQ6 (ORCPT ); Wed, 7 Feb 2007 05:16:58 -0500 Received: from postfix2-g20.free.fr ([212.27.60.43]:44339 "EHLO postfix2-g20.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161133AbXBGKQ5 (ORCPT ); Wed, 7 Feb 2007 05:16:57 -0500 Message-ID: <45C9A666.7010703@free.fr> Date: Wed, 07 Feb 2007 11:13:58 +0100 From: John User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061108 SeaMonkey/1.0.6 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org CC: mingo@elte.hu, tglx@timesys.com, johnstul@us.ibm.com, akpm@osdl.org, linux.kernel@free.fr Subject: Re: One-shot high-resolution POSIX timer periodically late References: <45C1BE5C.9050001@free.fr> <20070206123716.GA8481@elte.hu> In-Reply-To: <20070206123716.GA8481@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1403 Lines: 42 Ingo Molnar wrote: > John wrote: > >> Ingo Molnar wrote: >> >>> 2.6.18-rt7 is pretty old, do you see the problem in 2.6.20-rc6-rt5 too? >> >> Ingo, Thomas, >> >> I cannot reproduce in 2.6.20-rc6-rt6, but it is not strictly an >> apples-to-apples comparison because I get a tsc clocksource in >> 2.6.20-rc6-rt6, and an acpi_pm clocksource in 2.6.18.6-rt7. > > That suggests that the TSC was not deemed reliable by the newer kernel, > which almost always means it's not realiable. I think the problems you > were seeing are consistent with TSC being non-monotonic - so the fix is > to not use the TSC - and the newer kernel does this automatically. Ingo, Perhaps you've mis-read my message? *2.6.18.6-rt7* installed an acpi_pm clocksource. When I used a boot parameter to force the clocksource to tsc, the high-resolution timer infrastructure broke (timers expired several *ms* too late). On the other hand, *2.6.20-rc6-rt6* and *2.6.20-rt2* both installed a tsc clock source, and it works. Therefore, it is not the newer kernel that ignored the tsc, but the older kernel. Thus I don't know what to make of your comment :-) Regards, John - 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/