Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753555Ab3DVAuj (ORCPT ); Sun, 21 Apr 2013 20:50:39 -0400 Received: from mga14.intel.com ([143.182.124.37]:31565 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573Ab3DVAui convert rfc822-to-8bit (ORCPT ); Sun, 21 Apr 2013 20:50:38 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,521,1363158000"; d="scan'208";a="230068532" From: "Pan, Zhenjie" To: Don Zickus , Stephane Eranian CC: Peter Zijlstra , "paulus@samba.org" , "mingo@redhat.com" , "acme@ghostprotocols.net" , "akpm@linux-foundation.org" , "tglx@linutronix.de" , "Liu, Chuansheng" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v2] NMI: fix NMI period is not correct when cpu frequency changes issue. Thread-Topic: [PATCH v2] NMI: fix NMI period is not correct when cpu frequency changes issue. Thread-Index: Ac46b5lX48efHbUtRT2d/NJzqZ6DWQBdzKSAAAC9ZQAAA1VkgAC+rv5A Date: Mon, 22 Apr 2013 00:50:34 +0000 Message-ID: References: <1366285369.19383.19.camel@laptop> <20130418133927.GJ79013@redhat.com> In-Reply-To: <20130418133927.GJ79013@redhat.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1291 Lines: 28 > I believe it mattered to the Chrome folks. They want the watchdog to be as > tight as possible so the user experience isn't a hang but a quick reboot > instead. They like setting the watchdog to something like 2 seconds. > > There was a patch a few months ago that tried to hack around this issue and I > suggested this approach as a better solution. I forgot what the original > problem was. Perhaps someone can jump in and explain the problem being > solved (other than the watchdog isn't always 10 seconds)? > > Cheers, > Don Yes, I also think the period is important sometimes. As I mentioned before, the case I meet is: When the system hang with interrupt disabled, we use NMI to detect. Then it will find hard lockup and cause a panic. Panic is very important for debug these kind of issues. But if cpu frequency change, the period will be 2 times, 3 times even more.(if cpu can down from 2.0GHz to 200MHz, will be 10 times, it's a very big deviation) This make watchdog reset happen before hard lockup detect. Thanks Pan Zhenjie -- 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/