Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755298AbZFHI6c (ORCPT ); Mon, 8 Jun 2009 04:58:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751506AbZFHI6Z (ORCPT ); Mon, 8 Jun 2009 04:58:25 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:49759 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751308AbZFHI6Y (ORCPT ); Mon, 8 Jun 2009 04:58:24 -0400 Date: Mon, 8 Jun 2009 10:58:19 +0200 From: Ingo Molnar To: Dave Young Cc: Linux Kernel Mailing List , Andrew Morton , Linus Torvalds Subject: Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase Message-ID: <20090608085819.GH6372@elte.hu> References: <20090608081439.GB6372@elte.hu> <20090608084611.GD6372@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3075 Lines: 74 * Dave Young wrote: > On Mon, Jun 8, 2009 at 4:46 PM, Ingo Molnar wrote: > > > > * Dave Young wrote: > > > >> On Mon, Jun 8, 2009 at 4:14 PM, Ingo Molnar wrote: > >> > > >> > * Dave Young wrote: > >> > > >> >> Add a halt_delay module parameter in printk.c used to read the > >> >> printk messages in halt/poweroff/restart phase, delay each printk > >> >> messages by halt_delay milliseconds. It is useful for debugging if > >> >> there's no other way to dump kernel messages that time. > >> >> > >> >> The halt_delay max value is 65535, default value is 0, change it > >> >> by: > >> >> > >> >> echo xxx > /sys/module/printk/parameters/halt_delay > >> >> > >> >> Signed-off-by: Dave Young > >> >> --- > >> >> Documentation/kernel-parameters.txt | ? ?5 +++++ > >> >> kernel/printk.c ? ? ? ? ? ? ? ? ? ? | ? 17 +++++++++++++++++ > >> >> 2 files changed, 22 insertions(+) > >> >> > >> >> --- linux-2.6.orig/kernel/printk.c ? ?2009-06-08 13:55:35.000000000 +0800 > >> >> +++ linux-2.6/kernel/printk.c 2009-06-08 13:56:23.000000000 +0800 > >> >> @@ -250,6 +250,22 @@ static inline void boot_delay_msec(void) > >> >> ?} > >> >> ?#endif > >> >> > >> >> +/* msecs delay after each halt/poweroff/restart phase printk, > >> >> + unsigned short is enough for delay in milliseconds */ > >> >> +static unsigned short halt_delay; > >> >> + > >> >> +static inline void halt_delay_msec(void) > >> >> +{ > >> >> + ? ? if (unlikely(halt_delay == 0 || !(system_state == SYSTEM_HALT > >> >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? || system_state == SYSTEM_POWER_OFF > >> >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? || system_state == SYSTEM_RESTART))) > >> >> + ? ? ? ? ? ? return; > >> > > >> > This is a tiny bit ugly (and goes into the vprintf path) but i > >> > can see no other way either - a system_state > SYSTEM_RUNNING > >> > check would needlessly include the suspend-to-disk state (which > >> > we dont want to include here). > >> > >> Can we move suspend-to-disk before halt state? > > > > Yes, we could do that - if all system_state uses are checked for > > side-effects - in particular comparisons. We have a few places that > > do 'if (system_state > SYSTEM_RUNNING)' - to designate 'shutdown > > state'. Now, if we have any use of > SYSTEM_SHUTDOWN that might > > break from such a reordering. > > > > I wouldnt expect such usage really, but it has to be checked. That > > would make this patch quite a bit cleaner. > > > > Mind sending a followup delta patch with this cleanup? > > I'm glad to check the system_state usage, then write a followup patch. I'd also suggest to add a comment to the constants, to make sure that when new system states are added, the ordering assumptions are not broken. Ingo -- 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/