Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754496AbZFHJA0 (ORCPT ); Mon, 8 Jun 2009 05:00:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753248AbZFHJAO (ORCPT ); Mon, 8 Jun 2009 05:00:14 -0400 Received: from mail-bw0-f213.google.com ([209.85.218.213]:64148 "EHLO mail-bw0-f213.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751506AbZFHJAN convert rfc822-to-8bit (ORCPT ); Mon, 8 Jun 2009 05:00:13 -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=xFUveQo99ppzf4DyQKsSRMyvLU6QmimNRx2bD3aZS6PPQ/EK0LFAUtCHBl/XVGMiKk r1HeD2dnVwE6UpAgNfgoqd/B0/K76C6F0jSb2pQTGBfXxkaToKNv8RUsjJXIcdBmRMkH NcYEadUI8ZN5FcojGm2Qyit8iYonA2CxZ+Hvk= MIME-Version: 1.0 In-Reply-To: <20090608085819.GH6372@elte.hu> References: <20090608081439.GB6372@elte.hu> <20090608084611.GD6372@elte.hu> <20090608085819.GH6372@elte.hu> Date: Mon, 8 Jun 2009 17:00:13 +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: 3305 Lines: 85 On Mon, Jun 8, 2009 at 4:58 PM, Ingo Molnar wrote: > > * 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. Fine. > >        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/