Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932119AbXAQJkp (ORCPT ); Wed, 17 Jan 2007 04:40:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932164AbXAQJkp (ORCPT ); Wed, 17 Jan 2007 04:40:45 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:59953 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932119AbXAQJko (ORCPT ); Wed, 17 Jan 2007 04:40:44 -0500 Date: Wed, 17 Jan 2007 10:39:17 +0100 From: Ingo Molnar To: Russell King Cc: linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [patch] fix emergency reboot: call reboot notifier list if possible Message-ID: <20070117093917.GA7538@elte.hu> References: <20070117091319.GA30036@elte.hu> <20070117092233.GA30197@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070117092233.GA30197@flint.arm.linux.org.uk> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -5.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-5.9 required=5.9 tests=ALL_TRUSTED,BAYES_00 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2713 Lines: 81 * Russell King wrote: > On Wed, Jan 17, 2007 at 10:13:19AM +0100, Ingo Molnar wrote: > > we dont call the reboot notifiers during emergency reboot mainly because > > it could be called from atomic context and reboot notifiers are a > > blocking notifier list. But actually the kernel is often perfectly > > reschedulable in this stage, so we could as well process the > > reboot_notifier_list. > > My experience has been that when there has been the need to use this > facility, the kernel hasn't been reschedulable. [...] this decision is totally automatic - so if your situation happens and the kernel isnt reschedulable, then the notifier chain wont be called and nothing changes from your perspective. Hm, perhaps this should be dependent on CONFIG_PREEMPT, to make sure preempt_count() is reliable? but from my perspective this patch fixes a real regression. updated patch attached below. Ingo --------------------> Subject: [patch] call reboot notifier list when doing an emergency reboot From: Ingo Molnar my laptop does not reboot unless the shutdown notifiers are called first. So the following command, which i use as a fast way to reboot into a new kernel: echo b > /proc/sysrq-trigger just hangs indefinitely after the kernel prints "System rebooting". the thing is, that the kernel is actually reschedulable in this stage, so we could as well process the reboot_notifier_list. (furthermore, on -rt kernels this place is preemptable even during SysRq-b) So just process the reboot notifier list if we are preemptable. This will shut disk caches and chipsets off. Signed-off-by: Ingo Molnar --- kernel/sys.c | 10 ++++++++++ 1 file changed, 10 insertions(+) Index: linux/kernel/sys.c =================================================================== --- linux.orig/kernel/sys.c +++ linux/kernel/sys.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include @@ -710,6 +711,15 @@ out_unlock: */ void emergency_restart(void) { + /* + * Call the notifier chain if we are not in an + * atomic context: + */ +#ifdef CONFIG_PREEMPT + if (!in_atomic() && !irqs_disabled()) + blocking_notifier_call_chain(&reboot_notifier_list, + SYS_RESTART, NULL); +#endif machine_emergency_restart(); } EXPORT_SYMBOL_GPL(emergency_restart); - 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/