Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753919AbZFHI3K (ORCPT ); Mon, 8 Jun 2009 04:29:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752905AbZFHI26 (ORCPT ); Mon, 8 Jun 2009 04:28:58 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:49797 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752818AbZFHI25 (ORCPT ); Mon, 8 Jun 2009 04:28:57 -0400 Date: Mon, 8 Jun 2009 01:28:45 -0700 From: Andrew Morton To: Ingo Molnar Cc: Dave Young , Linux Kernel Mailing List , Linus Torvalds Subject: Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase Message-Id: <20090608012845.9c428525.akpm@linux-foundation.org> In-Reply-To: <20090608081439.GB6372@elte.hu> References: <20090608081439.GB6372@elte.hu> 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 Content-Length: 2338 Lines: 59 On Mon, 8 Jun 2009 10:14:39 +0200 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). > > In theory we could turn system_state into a bitmask and have a > print_delay_mask check instead of these flags ... but that is a far > wider change and i'm not sure it's a net step forwards. > > I've applied your patch to tip:core/printk with small edits to the > changelog - Linus & Andrew is Cc:ed, should they have any > objections. Could we not put just a single delay in there, immediately prior to halting, restarting or poweroffing? -- 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/