Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751914AbYGYOBS (ORCPT ); Fri, 25 Jul 2008 10:01:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750934AbYGYOBF (ORCPT ); Fri, 25 Jul 2008 10:01:05 -0400 Received: from dgate10.fujitsu-siemens.com ([80.70.172.49]:1037 "EHLO dgate10.fujitsu-siemens.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750854AbYGYOBF (ORCPT ); Fri, 25 Jul 2008 10:01:05 -0400 DomainKey-Signature: s=s768; d=fujitsu-siemens.com; c=nofws; q=dns; h=X-SBRSScore:X-IronPort-AV:Received:X-IronPort-AV: Received:Received:Message-ID:Date:From:Organization: User-Agent:MIME-Version:To:CC:Subject:References: In-Reply-To:Content-Type:Content-Transfer-Encoding; b=EiEmuJc4EOpH5SAu0gIhBW3ZbC1TdxTo84RG7wkLXt9MiC8KYMeQs7LO kKjmfrBu7vs54MymCyDsMCs5qKmPeIaGYgtiBYsalMOn/Y1+Olp2br/zA /7H/lCnjhX08Dt1; X-SBRSScore: None X-IronPort-AV: E=Sophos;i="4.31,252,1215381600"; d="scan'208";a="23570009" X-IronPort-AV: E=Sophos;i="4.31,252,1215381600"; d="scan'208";a="32952246" Message-ID: <4889DCA4.4010800@fujitsu-siemens.com> Date: Fri, 25 Jul 2008 16:01:08 +0200 From: Martin Wilck Organization: Fujitsu Siemens Computers User-Agent: Thunderbird 2.0.0.15pre (X11/20080508) MIME-Version: 1.0 To: Cyrill Gorcunov CC: Thomas Gleixner , "linux-kernel@vger.kernel.org" , "H. Peter Anvin" , "Wichert, Gerhard" , "Maciej W. Rozycki" Subject: Re: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe (take 3) References: <20080724120512.GA21804@lenovo> <488889B6.9070707@fujitsu-siemens.com> <20080724143151.GA32422@lenovo> <20080724150116.GC32422@lenovo> <48889C14.4070408@fujitsu-siemens.com> <4889968E.6020000@fujitsu-siemens.com> <20080725100844.GA16698@lenovo> <4889C723.7050402@fujitsu-siemens.com> <20080725125950.GA28466@lenovo> <4889D767.5050709@fujitsu-siemens.com> <20080725134831.GB28466@lenovo> In-Reply-To: <20080725134831.GB28466@lenovo> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1599 Lines: 46 Cyrill Gorcunov wrote: > Martin, if I understood you right - this means your patch is not > needed? The patch would still be needed. Just the reported failure of my simplified patch on the old kernel would not have occurred in the current kernel. IOW, the patch is fine for the current kernel, but not for the old one. > Actually on 64bit mode APIC_DIVISOR is a bit hidden in > __setup_APIC_LVTT - you may see it as APIC_TDR_DIV_16 while setting > up divisor register. I was proposing patch for that but it leaded > to potetntial overflow (thanks Ingo for catching) so we leave it as > is. Maybe I miss something? The problem was not that the divisor 16 was used for the counter speed (APIC_TDR_DIV_16), but that the old code set the counter start value to (250000000/16) rather than just 250000000. That means the counter will underflow earlier. I am attaching a "take 3" patch which minimizes the risk of an underflow by using the maximum possible initial value for the APIC timer. Martin -- Martin Wilck PRIMERGY System Software Engineer FSC IP ESP DEV 6 Fujitsu Siemens Computers GmbH Heinz-Nixdorf-Ring 1 33106 Paderborn Germany Tel: ++49 5251 8 15113 Fax: ++49 5251 8 20209 Email: mailto:martin.wilck@fujitsu-siemens.com Internet: http://www.fujitsu-siemens.com Company Details: http://www.fujitsu-siemens.com/imprint.html -- 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/