Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753726AbZFHIhn (ORCPT ); Mon, 8 Jun 2009 04:37:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752966AbZFHIhf (ORCPT ); Mon, 8 Jun 2009 04:37:35 -0400 Received: from mail-bw0-f213.google.com ([209.85.218.213]:63206 "EHLO mail-bw0-f213.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752504AbZFHIhf convert rfc822-to-8bit (ORCPT ); Mon, 8 Jun 2009 04:37:35 -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=hiyNQCfADa4539MRjLlEG+A0S71bEUfyH08EKoDnh8/Gx/VuER2F2u5L0BRtzWdT53 ns5P6y5ok8BkpnLWfCiXaCai0S3GGXBeHLW6pxX9WJwAL3Ac9dNiRPZG//lcRkE47aA3 l3r7bL9t0cAM+SlE38tX1vwjwpnWftsZKFXuo= MIME-Version: 1.0 In-Reply-To: <20090608081439.GB6372@elte.hu> References: <20090608081439.GB6372@elte.hu> Date: Mon, 8 Jun 2009 16:37:35 +0800 Message-ID: Subject: Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase From: Dave Young To: Ingo Molnar Cc: Linux Kernel Mailing List , Andrew Morton , 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: 2387 Lines: 66 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? > > 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. > >        Ingo > -- 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/