From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755135Ab2IXMRT (ORCPT ); Mon, 24 Sep 2012 08:17:19 -0400 Received: from casper.infradead.org ([85.118.1.10]:37394 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755071Ab2IXMRR convert rfc822-to-8bit (ORCPT ); Mon, 24 Sep 2012 08:17:17 -0400 Message-ID: <1348489027.11847.53.camel@twins> Subject: Re: [PATCH 2/2] [RESEND] console: implement lockdep support for console_lock From: Peter Zijlstra To: Daniel Vetter Cc: LKML , Intel Graphics Development , DRI Development , Dave Airlie , Thomas Gleixner , Alan Cox Date: Mon, 24 Sep 2012 14:17:07 +0200 In-Reply-To: <1347923013-4253-2-git-send-email-daniel.vetter@ffwll.ch> References: <1347923013-4253-1-git-send-email-daniel.vetter@ffwll.ch> <1347923013-4253-2-git-send-email-daniel.vetter@ffwll.ch> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-09-18 at 01:03 +0200, Daniel Vetter wrote: > - In the printk code there's a special trylock, only used to kick off > the logbuffer printk'ing in console_unlock. But all that happens > while lockdep is disable (since printk does a few other evil > tricks). So no issue there, either. Not particularly evil, just plain broken. See this series: http://marc.info/?l=linux-kernel&m=132446644123326&w=2 In particular see patches 1-4. The problem with lockdep is that lockdep uses printk and printk's recursion stuff is utterly broken. Console drivers being on crack simply doesn't help :-) Note that I would never recommend drm/ksm to anybody who really cares about their console output.