Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754455AbZGUGAX (ORCPT ); Tue, 21 Jul 2009 02:00:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752977AbZGUGAU (ORCPT ); Tue, 21 Jul 2009 02:00:20 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:56413 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752857AbZGUGAT (ORCPT ); Tue, 21 Jul 2009 02:00:19 -0400 Message-ID: <4A65598D.7020808@cn.fujitsu.com> Date: Tue, 21 Jul 2009 14:00:45 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: "Eric W. Biederman" , Andrew Morton CC: Neil Horman , Vivek Goyal , Brayan Arraes , LKML Subject: Re: [PATCH] sysrq, kdump: fix regression, revert "simplify sysrq-c handler" References: <4A64672E.8020005@cn.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1316 Lines: 38 Eric W. Biederman wrote: > Lai Jiangshan writes: > >> 1) This fix breaks our tools. >> This fix changes the ABI. panic_on_oops is default 0, >> and a lots system do not specify the boot option "panic", >> thus, Sysrq-c will not cause CrashDump(Kdump) as expected. > > How does it break your tools? Sysrq-c is known for causing a CrashDump. This fix make Sysrq-c just causing an oops. An oops in process context just kills current task and does nothing. (panic_on_oops=0) Why we let a cleanup patch changes the kernel behavior so much? > >> 2) When CONFIG_KEXEC=n, Sysrq-c should become an invalid >> command like Sysrq-D(CONFIG_LOCKDEP, show-all-locks). >> But this fix makes it a valid command and let it do a >> hazard thing: cause a page fault(NULL dereference) in kernel. >> >> So, we revert this fix. > > The idea was to extend sysrq-d to also be a way of testing NULL > pointer dereferences. How is that a bad idea? > When CONFIG_KEXEC=n, Crashdump is not available, Sysrq-c should become an invalid command. -- 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/