Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752517AbaDUNUw (ORCPT ); Mon, 21 Apr 2014 09:20:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19411 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752372AbaDUNUr (ORCPT ); Mon, 21 Apr 2014 09:20:47 -0400 Date: Mon, 21 Apr 2014 08:30:32 -0400 From: Vivek Goyal To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, Eric Biederman , Motohiro Kosaki , Yoshihiro YUNOMAE , Satoru MORIYA , Andrew Morton , Tomoki Sekiyama Subject: Re: [PATCH v3] kernel/panic: Add "crash_kexec_post_notifiers" option for kdump after panic_notifers Message-ID: <20140421123032.GC22181@redhat.com> References: <20140421013348.6719.6959.stgit@ltc230.yrl.intra.hitachi.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140421013348.6719.6959.stgit@ltc230.yrl.intra.hitachi.co.jp> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 21, 2014 at 10:33:48AM +0900, Masami Hiramatsu wrote: > Add a "crash_kexec_post_notifiers" option to run kdump after running > panic_notifiers and dump kmsg. This can help rare situations which > kdump drops in failure because of unstable crashed kernel or hardware > failure (memory corruption on critical data/code), or the 2nd kernel > is already broken by the 1st kernel (it's a broken behavior, but who > can guarantee that the "crashed" kernel works correctly?). > > Usage: add "crash_kexec_post_notifiers" to kernel boot option. > > Note that this actually increases risks of the failure of kdump. > This option should be set only if you worry about the rare case > of kdump failure rather than increasing the chance of success. > > Changes from v2: > - Remove warning message according to Vivek's comment. > > Changes from v1: > - Rename late_kdump option to crash_kexec_post_notifiers. > - Remove unneeded warning message. > > Signed-off-by: Masami Hiramatsu > Acked-by: Motohiro Kosaki > Cc: Eric Biederman > Cc: Vivek Goyal > Cc: Andrew Morton > Cc: Yoshihiro YUNOMAE > Cc: Satoru MORIYA > Cc: Tomoki Sekiyama > --- > Documentation/kernel-parameters.txt | 8 ++++++++ > kernel/panic.c | 23 +++++++++++++++++++++-- > 2 files changed, 29 insertions(+), 2 deletions(-) I think let us do it. Quite a few people have been asking for allowing to run hook for saving kernel buffers to NVRAM before we transition into kdump kernel. I understand that it opens flood gate for every kind of hook to be executed but that's the not default and if user decides to set crash_kexec_post_notifiers, they understand that they are increasing the chances of kdump failures. If they decide to do that, they need to live with this trade-off. We have pushed back on this for a very long time. I guess it is time to give it a chance and see how does it go. Does it really help those who want to do run notifiers before kdump kicks in. Acked-by: Vivek Goyal Thanks Vivek > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 03e50b4..1df416b 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2339,6 +2339,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > timeout < 0: reboot immediately > Format: > > + crash_kexec_post_notifiers > + Run kdump after running panic-notifiers and dumping > + kmsg. This only for the users who doubt kdump always > + succeeds in any situation. > + Note that this also increases risks of kdump failure, > + because some panic notifiers can make the crashed > + kernel more unstable. > + > parkbd.port= [HW] Parallel port number the keyboard adapter is > connected to, default is 0. > Format: > diff --git a/kernel/panic.c b/kernel/panic.c > index d02fa9f..30c4a1c 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -32,6 +32,7 @@ static unsigned long tainted_mask; > static int pause_on_oops; > static int pause_on_oops_flag; > static DEFINE_SPINLOCK(pause_on_oops_lock); > +static bool crash_kexec_post_notifiers; > > int panic_timeout = CONFIG_PANIC_TIMEOUT; > EXPORT_SYMBOL_GPL(panic_timeout); > @@ -112,9 +113,11 @@ void panic(const char *fmt, ...) > /* > * If we have crashed and we have a crash kernel loaded let it handle > * everything else. > - * Do we want to call this before we try to display a message? > + * If we want to run this after calling panic_notifiers, pass > + * the "crash_kexec_post_notifiers" option to the kernel. > */ > - crash_kexec(NULL); > + if (!crash_kexec_post_notifiers) > + crash_kexec(NULL); > > /* > * Note smp_send_stop is the usual smp shutdown function, which > @@ -131,6 +134,15 @@ void panic(const char *fmt, ...) > > kmsg_dump(KMSG_DUMP_PANIC); > > + /* > + * If you doubt kdump always works fine in any situation, > + * "crash_kexec_post_notifiers" offers you a chance to run > + * panic_notifiers and dumping kmsg before kdump. > + * Note: since some panic_notifiers can make crashed kernel > + * more unstable, it can increase risks of the kdump failure too. > + */ > + crash_kexec(NULL); > + > bust_spinlocks(0); > > if (!panic_blink) > @@ -472,6 +484,13 @@ EXPORT_SYMBOL(__stack_chk_fail); > core_param(panic, panic_timeout, int, 0644); > core_param(pause_on_oops, pause_on_oops, int, 0644); > > +static int __init setup_crash_kexec_post_notifiers(char *s) > +{ > + crash_kexec_post_notifiers = true; > + return 0; > +} > +early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers); > + > static int __init oops_setup(char *s) > { > if (!s) > -- 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/