From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752588Ab3BQTjw (ORCPT ); Sun, 17 Feb 2013 14:39:52 -0500 Received: from e36.co.us.ibm.com ([32.97.110.154]:43732 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752395Ab3BQTjv (ORCPT ); Sun, 17 Feb 2013 14:39:51 -0500 Date: Sat, 16 Feb 2013 13:07:15 -0800 From: "Paul E. McKenney" To: Linus Torvalds Cc: "H. Peter Anvin" , Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Dave Jones , Hugh Dickins , Linux Kernel Mailing List , Paul McKenney Subject: Re: Debugging Thinkpad T430s occasional suspend failure. Message-ID: <20130216210715.GC3094@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130213193411.GA15928@redhat.com> <20130215011503.GA11914@redhat.com> <20130215174435.GA2792@linux.vnet.ibm.com> <20130216192554.GB7035@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13021719-7606-0000-0000-0000087F1198 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 16, 2013 at 11:46:59AM -0800, Linus Torvalds wrote: > On Sat, Feb 16, 2013 at 11:25 AM, Paul E. McKenney > wrote: > > > > Sorry for the delay in testing this, but there was a need to upgrade > > my laptop, and bozo here figured "why not go to 64 bits while I am at > > it?" -- and then proceeded to learn the hard way that it is necessary > > to do "make mrproper" before doing a build in 64-bit mode. :-/ > > Hmm. Our object file dependency check includes checking that the > compiler options are the same, but that's only true for normal C > files. Some of the other rules do *not* test the full range of config > options, so in general, if you change architecture etc models, you do > indeed want to make sure that you do a "make distclean" (aka "make > mrproper") or something like "git clean -dqfx". > > For a number of other files, we just depend on the normal make > timestamp logic, which means that "if the object file is newer than > the sources", we'll trust it. Which obviously doesn't work for cases > where the object file may have been generated under totally different > architecture rules.. > > (That said, what kind of old environment did you do this in? > stub32_sigaltstack was removed during the merge window, so I'm > assuming you applied my patch on top of plain 3.7 or something?) This was in a git tree 3.7-rc7. And stub32_sigaltstack is now gone, but perhaps I did something stupid that made it persist. Ah, the previous time I did a build directly out of this git tree might well have been before 3.8-rc, so maybe the .o file was from before? > > The kernel build system's way of telling you this at the moment is: > > > > arch/x86/built-in.o:(.rodata+0x4990): undefined reference to `stub32_sigaltstack' > > Adding Peter Anvin to the people, just in case he sees what's wrong > with the system call stub generation that keeps excessively old object > files around. If it's easy to fix, it might be worth trying to make it > ok to switch from i386 to x86-64 and back in the same tree. > > Peter? Not a big deal, but if you see something obvious, let's just > try to fix it, ok? > > > Anyway, with this patch, I see CPU stall warnings when running rcutorture > > as shown below. This is not a hard failure: > > Yeah, there's something wrong with the patch, I didn't bother trying > to figure it out for now. It also causes a hard failure with lockdep > (or lock proving/debugging, I'm not sure which one triggered it) - and > it happens too early to even see anything on the screen. Glad that it is not just me, then. ;-) > So I'd like to make that "downgrade from hardirq to softirq" atomic, > and I think it would clean up the crazy code too (currently it does a > *lot* of back-and-forth on the preempt flags), but I clearly missed > some case where we used a wrapper or two to add some tracepoint or a > RCU scheduling point. And I'm not going to worry about it right now, > since I'm preparing to make v3.8 soon. > > But if somebody spots the bug, holler. I must confess that your patch looked OK to me... Thanx, Paul