From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758309Ab2AEULS (ORCPT ); Thu, 5 Jan 2012 15:11:18 -0500 Received: from usindpps03.hds.com ([207.126.252.16]:56748 "EHLO usindpps03.hds.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755978Ab2AEULR convert rfc822-to-8bit (ORCPT ); Thu, 5 Jan 2012 15:11:17 -0500 From: Seiji Aguchi To: "Luck, Tony" , Don Zickus CC: "linux-kernel@vger.kernel.org" , Matthew Garrett , Vivek Goyal , "Chen, Gong" , "akpm@linux-foundation.org" , "Brown, Len" , "'ying.huang@intel.com'" <'ying.huang@intel.com'>, "'ak@linux.intel.com'" <'ak@linux.intel.com'>, "'hughd@chromium.org'" <'hughd@chromium.org'>, "'mingo@elte.hu'" <'mingo@elte.hu'>, "jmorris@namei.org" , "a.p.zijlstra@chello.nl" , "namhyung@gmail.com" , "dle-develop@lists.sourceforge.net" , Satoru Moriya Date: Thu, 5 Jan 2012 15:10:25 -0500 Subject: RE: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop() Thread-Topic: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop() Thread-Index: AQHMy9CqWb3Eal+luUidUg+JrwynPJX+IWHAgAAOOEA= Message-ID: <5C4C569E8A4B9B42A84A977CF070A35B2C5827B01D@USINDEVS01.corp.hds.com> References: <5C4C569E8A4B9B42A84A977CF070A35B2C5827AF7F@USINDEVS01.corp.hds.com> <5C4C569E8A4B9B42A84A977CF070A35B2C5827AF81@USINDEVS01.corp.hds.com> <3908561D78D1C84285E8C5FCA982C28FBB21@ORSMSX104.amr.corp.intel.com> In-Reply-To: <3908561D78D1C84285E8C5FCA982C28FBB21@ORSMSX104.amr.corp.intel.com> Accept-Language: ja-JP, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: ja-JP, en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Proofpoint-Spam-Details: rule=outbound_policy_notspam policy=outbound_policy score=0 spamscore=0 ipscore=0 suspectscore=2 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=6.0.2-1012030000 definitions=main-1201050226 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >Aren't you worried about the comment about smp_send_stop() not >being hardened to work in a panic situation? > /* > * Note smp_send_stop is the usual smp shutdown function, which > * unfortunately means it may not be hardened to work in a panic This comment is wrong because Don improved smp_send_stop() by switching REBOOT_VECTOR to NMI. And his patch has already merged to linux-next tree. http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=commitdiff;h=3603a2512f9e69dc87914ba922eb4a0812b21cd6 So, current smp_send_stop() is hardened to work in a panic situation. I will remove this wrong comment. Seiji >-----Original Message----- >From: Luck, Tony [mailto:tony.luck@intel.com] >Sent: Thursday, January 05, 2012 2:07 PM >To: Seiji Aguchi; Don Zickus >Cc: linux-kernel@vger.kernel.org; Matthew Garrett; Vivek Goyal; Chen, Gong; akpm@linux-foundation.org; Brown, Len; >'ying.huang@intel.com'; 'ak@linux.intel.com'; 'hughd@chromium.org'; 'mingo@elte.hu'; jmorris@namei.org; >a.p.zijlstra@chello.nl; namhyung@gmail.com; dle-develop@lists.sourceforge.net; Satoru Moriya >Subject: RE: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send_stop() > >- kmsg_dump(KMSG_DUMP_PANIC); >- > /* > * Note smp_send_stop is the usual smp shutdown function, which > * unfortunately means it may not be hardened to work in a panic >@@ -117,6 +115,8 @@ void panic(const char *fmt, ...) > */ > smp_send_stop(); > >+ kmsg_dump(KMSG_DUMP_PANIC); >+ > >Aren't you worried about the comment about smp_send_stop() not >being hardened to work in a panic situation? > >If it does work - we are clearly much better off moving the >kmsg_dump() call down like this. It makes life much simpler >and cleaner to work with just one running cpu. > >But if something goes wrong - we might not see the dump at all! > >How do we compare these cases and decide that it is better to >trust that smp_send_stop() will return? > >-Tony