Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755426AbZFGOcc (ORCPT ); Sun, 7 Jun 2009 10:32:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753742AbZFGOcZ (ORCPT ); Sun, 7 Jun 2009 10:32:25 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:49574 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752645AbZFGOcY (ORCPT ); Sun, 7 Jun 2009 10:32:24 -0400 Date: Sun, 7 Jun 2009 16:32:21 +0200 From: Ingo Molnar To: Dave Young Cc: Linux Kernel Mailing List , Andrew Morton , Linus Torvalds Subject: Re: [PATCH v2] printk: add halt_delay parameter for printk delay in halt phase Message-ID: <20090607143221.GE21340@elte.hu> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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: 1899 Lines: 62 * 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 > --- > kernel/printk.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > --- linux-2.6.orig/kernel/printk.c 2009-06-03 10:16:55.000000000 +0800 > +++ linux-2.6/kernel/printk.c 2009-06-03 10:32:43.000000000 +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; > + > + mdelay(halt_delay); > +} > + > +module_param(halt_delay, ushort, S_IRUGO | S_IWUSR); > + > /* > * Commands to do_syslog: > * > @@ -649,6 +665,7 @@ asmlinkage int vprintk(const char *fmt, > char *p; > > boot_delay_msec(); > + halt_delay_msec(); > > preempt_disable(); > /* This stops the holder of console_sem just where we want him */ Looks nice now - but please also add a description to Documentation/kernel-parameters.txt. Thanks, 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/