Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765480Ab3DDXlc (ORCPT ); Thu, 4 Apr 2013 19:41:32 -0400 Received: from mail-lb0-f182.google.com ([209.85.217.182]:62906 "EHLO mail-lb0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765146Ab3DDXlb (ORCPT ); Thu, 4 Apr 2013 19:41:31 -0400 MIME-Version: 1.0 In-Reply-To: <515DBB00.20208@sr71.net> References: <515DBB00.20208@sr71.net> Date: Fri, 5 Apr 2013 01:41:29 +0200 Message-ID: Subject: Re: sched/cputime: sig->prev_stime underflow From: Frederic Weisbecker To: Dave Hansen Cc: LKML , Ingo Molnar , Peter Zijlstra , Hidetoshi Seto , Stanislaw Gruszka Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1413 Lines: 35 2013/4/4 Dave Hansen : > With the 3.9-rcs (and probably much earlier) I'm seeing some weird top > output where the cpu time "spent" is millions of hours: > > 445 root 20 0 0 0 0 S 0 0.0 5124095h kworker/45:1 > 404 root 20 0 0 0 0 S 0 0.0 5124095h kworker/4:1 > > I see it mostly with kernel threads, but it doesn't seem to happen on my > distro kernel (3.5 era). The suspect code is in thread_group_times(): > > sig->prev_stime = max(sig->prev_stime, rtime - sig->prev_utime); > > In my case, I caught it with rtime=34 and sig->prev_utime=35. This code > _looks_ to be pretty mature, coming in at commit 0cf55e1e in 2009. The > system I'm running on _does_ have some non-sync'd TSCs, but they are at > least being detected, so I expect the fallout to be minimal: > > tsc: Marking TSC unstable due to check_tsc_sync_source failed > > config: > > http://sr71.net/~dave/linux/config-bigbox-04042013.txt > > The dumb fix here would seem to be to just check "rtime < > sig->prev_utime". Any thoughts? Hi Dave, Does this patch fix the issue for you? https://lkml.org/lkml/2013/4/4/112 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/