Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754970AbZFHImh (ORCPT ); Mon, 8 Jun 2009 04:42:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752504AbZFHIma (ORCPT ); Mon, 8 Jun 2009 04:42:30 -0400 Received: from mail-bw0-f213.google.com ([209.85.218.213]:64152 "EHLO mail-bw0-f213.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751781AbZFHIm3 convert rfc822-to-8bit (ORCPT ); Mon, 8 Jun 2009 04:42:29 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=AtnM60czhGtW4EPDV/b1/6bkzn2uJY8I75My4rl8VyZbZfm7zfHhMSNh806o0cQdNt n1vJX6SvlFG5iTBKOcFyhD3xPZpVG1FkSkHs9KJLYznacVoCKjEU1VRoZarSsBmyPkYx KoSIfMNgLyUCX9oMYkKYS7+NjNtddC5miAH7o= MIME-Version: 1.0 In-Reply-To: <20090608012845.9c428525.akpm@linux-foundation.org> References: <20090608081439.GB6372@elte.hu> <20090608012845.9c428525.akpm@linux-foundation.org> Date: Mon, 8 Jun 2009 16:42:29 +0800 Message-ID: Subject: Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase From: Dave Young To: Andrew Morton Cc: Ingo Molnar , Linux Kernel Mailing List , Linus Torvalds Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2663 Lines: 65 On Mon, Jun 8, 2009 at 4:28 PM, Andrew Morton wrote: > 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? But, then prink messages will still flush too fast for us to see the detail. -- Regards dave -- 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/