From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756101Ab1FIVHo (ORCPT ); Thu, 9 Jun 2011 17:07:44 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:34165 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753837Ab1FIVHn (ORCPT ); Thu, 9 Jun 2011 17:07:43 -0400 Date: Thu, 9 Jun 2011 14:07:14 -0700 From: Andrew Morton To: Peter Zijlstra Cc: Ingo Molnar , Linus Torvalds , Thomas Gleixner , linux-kernel@vger.kernel.org, efault@gmx.de, Arne Jansen Subject: Re: [PATCH 1/3] printk: Release console_sem after logbuf_lock Message-Id: <20110609140714.fc9ea187.akpm@linux-foundation.org> In-Reply-To: <1307652883.2497.1028.camel@laptop> References: <20110609130647.937204592@chello.nl> <20110609131307.493181962@chello.nl> <20110609130617.f8aca966.akpm@linux-foundation.org> <20110609202707.GA28951@elte.hu> <1307652883.2497.1028.camel@laptop> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 09 Jun 2011 22:54:43 +0200 Peter Zijlstra wrote: > On Thu, 2011-06-09 at 22:27 +0200, Ingo Molnar wrote: > > > > > @@ -1271,8 +1273,8 @@ void console_unlock(void) > > > > if (unlikely(exclusive_console)) > > > > exclusive_console = NULL; > > > > > > > > - up(&console_sem); > > > > spin_unlock_irqrestore(&logbuf_lock, flags); > > > > + up(&console_sem); > > > > if (wake_klogd) > > > > wake_up_klogd(); > > > > } > > > > > > I have a horrible feeling that I put the up() inside logbuf_lock for > > > Special And Cunning Reasons. But I'm struggling to work out what they > > > might have been and my archives only go back to October 2000(!). > > > > > > Hate it when that happens. > > > > Heh, here's what i told Peter two days ago when i saw that chunk: > > > > => Subject: printk: Release console_sem after logbuf_lock > > => i have some vague memories about some sort of complication in that area ... > > => but don't remember the specifics > > => only a 'there be dragons' mental marker > > Right, my reply was that I couldn't convince myself unlock order could > make a difference, but clearly I can easily have missed something > subtle. I wish I could find the darned patch. I have a file here no-console-lock-2.patch which was last diffed on October 7, 1999 but it has no changelog :( But this: http://lkml.indiana.edu/hypermail/linux/kernel/0109.2/0127.html is Sep 2001 and I have an earlier (unchangelogged) no-console-lock.patch diffed against 2.4.2 in March 2001. It's odd that the patch (and changelog) don't appear in my lkml archives. Sigh, http://www.youtube.com/watch?v=oO3YmT2d-8k