Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756781AbZFIBfu (ORCPT ); Mon, 8 Jun 2009 21:35:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752036AbZFIBfl (ORCPT ); Mon, 8 Jun 2009 21:35:41 -0400 Received: from mail-ew0-f210.google.com ([209.85.219.210]:52195 "EHLO mail-ew0-f210.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751536AbZFIBfl convert rfc822-to-8bit (ORCPT ); Mon, 8 Jun 2009 21:35:41 -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=gQFboYHo++zHhNapa1Hx3ApSm24zDHJlXx0rfq5NmHMID5KUWDojc8q5EORoVD7Gsx rwC03DvI9JxiA8gtdiHBGEEFBlO/1PeH5Y1cr2VXQaNS527NnuJjTQP2VIfOTrFAiXCo /TH/Re5Kqn+OFf3XKL6Lo6st8wgpyvkCapN7A= MIME-Version: 1.0 In-Reply-To: References: <20090608081439.GB6372@elte.hu> <20090608012845.9c428525.akpm@linux-foundation.org> <20090608084807.GE6372@elte.hu> <20090608092607.8b331bf0.akpm@linux-foundation.org> <20090608171501.GA15399@elte.hu> <20090608143913.749e19c5.akpm@linux-foundation.org> Date: Tue, 9 Jun 2009 09:35:42 +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@vger.kernel.org, torvalds@linux-foundation.org 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: 2601 Lines: 76 On Tue, Jun 9, 2009 at 9:01 AM, Dave Young wrote: > On Tue, Jun 9, 2009 at 5:39 AM, Andrew Morton wrote: >> On Mon, 8 Jun 2009 19:15:01 +0200 >> Ingo Molnar wrote: >> >>> > questions: is it possible for interrupts to be disabled at this >>> > time? If so, can we get an NMI watchdog hit? >>> >>> no, we generally turn off the nmi watchdog during shutdown, disable >>> the lapic and io-apic, etc. >> >> Is x86 the only architecture which implements an NMI watchdog? >> >>> > Is the softlockup detector still running and if so, can it >>> > trigger? >>> >>> in (non-emergency) reboot, last i checked, we stopped all other CPUs >>> first, and then killed the current one. There's no chance for the >>> watchdog thread to run. >> >> OK, but...  See below. >> >>> Anyway ... you seem to be uncomfortable about this patch - should i >>> delay it for now to let it all play out? We are close to the merge >>> window. >> >> I'm OK - I'm just bouncing ideas and questions off you guys, to make sure >> that we've thought this through all the way. >> >> Here's another: why is it a boot option rather than a runtime-tunable? >> A /proc tweakable is generally preferable because it avoids the >> oh-crap-i-forgot-to-edit-grub.conf thing.  And we could perhaps then >> remove all those system_state tests: userspace sets printk_delay >> immediately prior to running halt/reboot/etc? > > Andrew, thanks your comments. > I original intention is to use not boot options but sysfs interface. > Do you perfer proc? > without system_state testing we will have to consider the NMI watchdog > and softlockup issue. > >> >> Plus the feature becomes more general - perhaps there are use cases >> where people want to slow down printks, such as: kernel goes oops, data >> scrolls off, serial console/netconsole unavailable.  pause_on_oops is >> supposed to help here but last time I tried it, it kinda didn't work, >> plus pause_on_oops doesn't solve the data-scrolled-off problem. > > Seems make sense And, if making it a general feature, I think maybe delay per screen (ie. 25 lines) is a good way. > >> >> Thirdly, if we do this as a general /proc/printk_delay thing, perhaps >> it can be consolidated with the existing boot_delay= implementation. >> > > > > -- > Regards > dave > -- 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/