From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932337AbYEUL33 (ORCPT ); Wed, 21 May 2008 07:29:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757566AbYEUL3R (ORCPT ); Wed, 21 May 2008 07:29:17 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:57951 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754195AbYEUL3Q (ORCPT ); Wed, 21 May 2008 07:29:16 -0400 Subject: Re: /proc/lock_stat "stuck" From: Peter Zijlstra To: "Alan D. Brunelle" Cc: "linux-kernel@vger.kernel.org" In-Reply-To: <483402CE.9000706@hp.com> References: <483313DD.2020904@hp.com> <1211361380.6463.63.camel@lappy.programming.kicks-ass.net> <483402CE.9000706@hp.com> Content-Type: text/plain Date: Wed, 21 May 2008 13:29:02 +0200 Message-Id: <1211369342.6463.93.camel@lappy.programming.kicks-ass.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2008-05-21 at 07:09 -0400, Alan D. Brunelle wrote: > Peter Zijlstra wrote: > > On Tue, 2008-05-20 at 14:09 -0400, Alan D. Brunelle wrote: > >> I'm attempting to use /proc/lock_stat to gather some information during > >> some benchmarking runs, but what I find happens is as follows: > >> > >> 1. I boot the system - 2.6.26-rc3 kernel + CONFIG_LOCK_STAT=y > >> > >> 2. I can then look at /proc/lock_stat, and it has valid-looking values > >> > >> 3. I wait a while, do some stuff, but when I look at /proc/lock_stat > >> again the values have not changed. > >> > >> 4. If I clear the counters - echo 0 > /proc/lock_stat - the counters > >> never increase, and no information besides the headers are output when I > >> cat /proc/lock_stat. > >> > >> > >> Is there something that one needs to do to get counter updates? > > > > Did you get lockdep warnings? Those disable all lock debugging, > > including lockstat. > > Hi Peter - > > Yesterday, during boots I /was/ getting a problem with NVIDIA ck804xrom > registration problems - "Unable to register resource" - it did produce > a stack trace w/ lock calls in the stack. Since then I've cut /way/ back > on my .config, and I don't see that problem anymore, and the lock stats > seem to be updating correctly with this new .config. [If I have time > later today, I'll go back to the old .config and try to track down the > ck804xrom issue.] > > Thanks for the hint about watching for lockdep issues, > Alan You might like to 'test' these two patches :-) Subject: lockstat: warn about disabled lock debugging From: Peter Zijlstra Avoid confusion and clearly state lock debugging got disabled. Signed-off-by: Peter Zijlstra --- kernel/lockdep_proc.c | 4 ++++ 1 file changed, 4 insertions(+) Index: linux-2.6/kernel/lockdep_proc.c =================================================================== --- linux-2.6.orig/kernel/lockdep_proc.c +++ linux-2.6/kernel/lockdep_proc.c @@ -516,6 +516,10 @@ static void seq_stats(struct seq_file *m static void seq_header(struct seq_file *m) { seq_printf(m, "lock_stat version 0.2\n"); + + if (unlikely(!debug_locks)) + seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n"); + seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1)); seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s " "%14s %14s\n", Subject: lockstat: fix contention points From: Peter Zijlstra blatantly stupid bug.. Signed-off-by: Peter Zijlstra --- kernel/lockdep.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6/kernel/lockdep.c =================================================================== --- linux-2.6.orig/kernel/lockdep.c +++ linux-2.6/kernel/lockdep.c @@ -2791,7 +2791,7 @@ found_it: stats = get_lock_stats(hlock->class); if (point < ARRAY_SIZE(stats->contention_point)) - stats->contention_point[i]++; + stats->contention_point[point]++; if (lock->cpu != smp_processor_id()) stats->bounces[bounce_contended + !!hlock->read]++; put_lock_stats(stats);