From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937689Ab0CPKNB (ORCPT ); Tue, 16 Mar 2010 06:13:01 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:58693 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937665Ab0CPKM7 (ORCPT ); Tue, 16 Mar 2010 06:12:59 -0400 Date: Tue, 16 Mar 2010 11:12:51 +0100 From: Ingo Molnar To: Eric Dumazet Cc: Colin Ian King , Peter Zijlstra , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH] softlockup: stop spurious softlockup messages due to overflow Message-ID: <20100316101251.GM7961@elte.hu> References: <1268661673-21638-1-git-send-email-colin.king@canonical.com> <1268663388.3154.30.camel@edumazet-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1268663388.3154.30.camel@edumazet-laptop> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Eric Dumazet wrote: > Le lundi 15 mars 2010 ?? 14:01 +0000, Colin Ian King a ??crit : > > Ensure additions on touch_ts do not overflow. This can occur when > > the top 32 bits of the TSC reach 0xffffffff causing additions to > > touch_ts to overflow and this in turn generates spurious softlockup > > warnings. > > > > Signed-off-by: Colin Ian King > > --- > > kernel/softlockup.c | 6 +++--- > > 1 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/softlockup.c b/kernel/softlockup.c > > index 0d4c789..90d9aa0 100644 > > --- a/kernel/softlockup.c > > +++ b/kernel/softlockup.c > > @@ -111,10 +111,10 @@ int proc_dosoftlockup_thresh(struct ctl_table *table, int write, > > void softlockup_tick(void) > > { > > int this_cpu = smp_processor_id(); > > - unsigned long touch_ts = per_cpu(softlockup_touch_ts, this_cpu); > > + unsigned long long touch_ts = per_cpu(softlockup_touch_ts, this_cpu); > > unsigned long print_ts; > > struct pt_regs *regs = get_irq_regs(); > > - unsigned long now; > > + unsigned long long now; > > > > /* Is detection switched off? */ > > if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) { > > @@ -165,7 +165,7 @@ void softlockup_tick(void) > > per_cpu(softlockup_print_ts, this_cpu) = touch_ts; > > > > spin_lock(&print_lock); > > - printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", > > + printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %llus! [%s:%d]\n", > > this_cpu, now - touch_ts, > > current->comm, task_pid_nr(current)); > > print_modules(); > > This looks wrong, touch_ts is a long, not a long long. Could be increased to long long - but that's probably overkill as the touch_ts is in seconds, so the scope of comparisons should never truly get even close to ~2^31. > You probably want to change the comparisons instead. > > if (now > touch_ts + softlockup_thresh/2) > wake_up_process(per_cpu(softlockup_watchdog, this_cpu)); > if (now <= (touch_ts + softlockup_thresh)) > return; > > -> > > if ((long)(now - touch_ts) > softlockup_thresh/2) > wake_up_process(per_cpu(softlockup_watchdog, this_cpu)); > if ((long)(now - touch_ts) <= softlockup_thresh)) > return; > > Or use standard time_after()/time_before() macros. Yeah, time_after/before would work better i suspect. Thanks, Ingo