From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757914Ab0BLXBm (ORCPT ); Fri, 12 Feb 2010 18:01:42 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:43596 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756133Ab0BLXBk (ORCPT ); Fri, 12 Feb 2010 18:01:40 -0500 Date: Fri, 12 Feb 2010 15:00:27 -0800 From: Andrew Morton To: Jason Wessel Cc: linux-kernel@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, mingo@elte.hu Subject: Re: [PATCH 26/28] kdb,panic,debug_core: Allow the debug core to receive a panic before smp_send_stop() Message-Id: <20100212150027.f875bbde.akpm@linux-foundation.org> In-Reply-To: <1266014143-29444-27-git-send-email-jason.wessel@windriver.com> References: <1266014143-29444-1-git-send-email-jason.wessel@windriver.com> <1266014143-29444-27-git-send-email-jason.wessel@windriver.com> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 12 Feb 2010 16:35:41 -0600 Jason Wessel wrote: > It is highly desirable to trap into kdb on panic, s/kdb/kgdb/ But is it necessary to do it in-kernel? Why not just put a breakpoint at panic(), add that to your .gdbinit? > diff --git a/kernel/panic.c b/kernel/panic.c > index c787333..428d15b 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -66,10 +66,13 @@ NORET_TYPE void panic(const char * fmt, ...) > */ > preempt_disable(); > > - bust_spinlocks(1); > va_start(args, fmt); > vsnprintf(buf, sizeof(buf), fmt, args); > va_end(args); > + > + atomic_notifier_call_chain(&panic_notifier_list, 0, buf); > + > + bust_spinlocks(1); > printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf); > #ifdef CONFIG_DEBUG_BUGVERBOSE > dump_stack(); > @@ -91,8 +94,6 @@ NORET_TYPE void panic(const char * fmt, ...) > */ > smp_send_stop(); > > - atomic_notifier_call_chain(&panic_notifier_list, 0, buf); > - > bust_spinlocks(0); > > if (!panic_blink) So the notifier call now happens before all the printks and the kexec and kmsg_dump handling. What effect does this have upon the code which implements kexec and kmsg_dump?