Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754264AbZGWNhu (ORCPT ); Thu, 23 Jul 2009 09:37:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754220AbZGWNht (ORCPT ); Thu, 23 Jul 2009 09:37:49 -0400 Received: from mx2.redhat.com ([66.187.237.31]:47825 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754219AbZGWNhs (ORCPT ); Thu, 23 Jul 2009 09:37:48 -0400 Date: Thu, 23 Jul 2009 09:37:32 -0400 From: Vivek Goyal To: Hidetoshi Seto Cc: linux-kernel@vger.kernel.org, Lai Jiangshan , "Ken'ichi Ohmichi" , Neil Horman , Brayan Arraes , "Eric W. Biederman" , Andrew Morton Subject: Re: [PATCH] sysrq, kdump: Make sysrq-c consistent Message-ID: <20090723133732.GB9215@redhat.com> References: <4A67F12A.9060204@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A67F12A.9060204@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4546 Lines: 113 On Thu, Jul 23, 2009 at 02:12:10PM +0900, Hidetoshi Seto wrote: > [ based on 2.6.31-rc4 ] > > Recent commit d6580a9f15238b87e618310c862231ae3f352d2d changed the > behavior of sysrq-c to unconditional dereference of NULL pointer. > So in cases with CONFIG_KEXEC, where crash_kexec() was directly called > from sysrq-c before, now it can be said that a step of "real oops" was > inserted before starting kdump. > > However, in contrast to oops via SysRq-c from keyboard which results > in panic due to in_interrupt(), oops via "echo c > /proc/sysrq-trigger" > will not become panic unless panic_on_oops=1. It means that even if > dump is properly configured to be taken on panic, the sysrq-c from proc > interface might not start crashdump while the sysrq-c from keyboard can > start crashdump. This confuses traditional users of kdump, i.e. people > who expect sysrq-c to do common behavior in both of the keyboard and > proc interface. > > This patch brings the keyboard and proc interface behavior of sysrq-c > in line, by forcing panic_on_oops=1 before oops in sysrq-c handler. > > And some updates in documentation are included, to clarify that there > is no longer dependency with CONFIG_KEXEC, and that now the system can > just crash by sysrq-c if no dump mechanism is configured. > > Signed-off-by: Hidetoshi Seto > Cc: Lai Jiangshan > Cc: Ken'ichi Ohmichi > Cc: Neil Horman > Cc: Vivek Goyal > Cc: Brayan Arraes > Cc: Eric W. Biederman > Cc: Andrew Morton Looks good to me. Acked-by: Vivek Goyal Thanks Vivek > --- > Documentation/sysrq.txt | 7 ++++--- > drivers/char/sysrq.c | 8 +++++--- > 2 files changed, 9 insertions(+), 6 deletions(-) > > diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt > index cf42b82..d56a017 100644 > --- a/Documentation/sysrq.txt > +++ b/Documentation/sysrq.txt > @@ -66,7 +66,8 @@ On all - write a character to /proc/sysrq-trigger. e.g.: > 'b' - Will immediately reboot the system without syncing or unmounting > your disks. > > -'c' - Will perform a kexec reboot in order to take a crashdump. > +'c' - Will perform a system crash by a NULL pointer dereference. > + A crashdump will be taken if configured. > > 'd' - Shows all locks that are held. > > @@ -141,8 +142,8 @@ useful when you want to exit a program that will not let you switch consoles. > re'B'oot is good when you're unable to shut down. But you should also 'S'ync > and 'U'mount first. > > -'C'rashdump can be used to manually trigger a crashdump when the system is hung. > -The kernel needs to have been built with CONFIG_KEXEC enabled. > +'C'rash can be used to manually trigger a crashdump when the system is hung. > +Note that this just triggers a crash if there is no dump mechanism available. > > 'S'ync is great when your system is locked up, it allows you to sync your > disks and will certainly lessen the chance of data loss and fscking. Note > diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c > index 0db3585..5d7a02f 100644 > --- a/drivers/char/sysrq.c > +++ b/drivers/char/sysrq.c > @@ -35,7 +35,6 @@ > #include > #include > #include > -#include > #include > #include > > @@ -124,9 +123,12 @@ static struct sysrq_key_op sysrq_unraw_op = { > static void sysrq_handle_crash(int key, struct tty_struct *tty) > { > char *killer = NULL; > + > + panic_on_oops = 1; /* force panic */ > + wmb(); > *killer = 1; > } > -static struct sysrq_key_op sysrq_crashdump_op = { > +static struct sysrq_key_op sysrq_crash_op = { > .handler = sysrq_handle_crash, > .help_msg = "Crash", > .action_msg = "Trigger a crash", > @@ -401,7 +403,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = { > */ > NULL, /* a */ > &sysrq_reboot_op, /* b */ > - &sysrq_crashdump_op, /* c & ibm_emac driver debug */ > + &sysrq_crash_op, /* c & ibm_emac driver debug */ > &sysrq_showlocks_op, /* d */ > &sysrq_term_op, /* e */ > &sysrq_moom_op, /* f */ > -- > 1.6.0 -- 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/