From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755397Ab0ETJzW (ORCPT ); Thu, 20 May 2010 05:55:22 -0400 Received: from www.tglx.de ([62.245.132.106]:58139 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755344Ab0ETJzU (ORCPT ); Thu, 20 May 2010 05:55:20 -0400 Date: Thu, 20 May 2010 11:47:32 +0200 (CEST) From: Thomas Gleixner To: Sujit K M cc: "Nikita V. Youshchenko" , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: PREEMPT_RT (2.6.33-rt17) disabled printk-to-console after console_init In-Reply-To: Message-ID: References: <201005201233.56877@zigzag.lvk.cs.msu.su> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Please stop top posting ! On Thu, 20 May 2010, Sujit K M wrote: > >>> Well, obviously it's unsafe if you remove safety checks. And if you > >>> care to look at the changelog of kernel/printk.c you'll find out why. > >> > >> Hmm... did a quick look and could not find anything related there. > >> Could you please give a pointer? Gah, yes. The changelog of the commit is not really helpful. Let me explain: The console drivers might take locks, which are converted to "sleeping locks" in preempt-rt. As a result we cannot call into those drivers from atomic contexts. And that's what the checks in the printk code prevent. Hope that helps. Thanks, tglx