Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752960AbaJTI1x (ORCPT ); Mon, 20 Oct 2014 04:27:53 -0400 Received: from mail-vc0-f171.google.com ([209.85.220.171]:62579 "EHLO mail-vc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752593AbaJTI1v (ORCPT ); Mon, 20 Oct 2014 04:27:51 -0400 MIME-Version: 1.0 In-Reply-To: <1413722356.2991.8.camel@localhost.localdomain> References: <1413722356.2991.8.camel@localhost.localdomain> Date: Mon, 20 Oct 2014 10:27:50 +0200 Message-ID: Subject: Re: [uml-devel] [UM] Long loop in __getnsdayoftime() after resume from ram From: Richard Weinberger To: Thomas Meyer Cc: user-mode-linux-devel , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 19, 2014 at 2:39 PM, Thomas Meyer wrote: > Hello, > > in UML kernel I get a long cpu using loop in __getnstimeofday() > (kernel/time/timekeeping.c:315) in the call of timespec_add_ns(), > when I left the host kernel suspended to ram for a few hours and resume > again. > this is because it seems like the tk->xtime_sec wasn't updated yet, but > the nsecs were. nsecs can be as high as 8111000111000111000l > > the function timespec_add_ns() (include/linux/time.h:266) will call > __iter_div_u64_rem() which has an optimized loop for the case > that the dividend is not much bigger as the divisior. > but this isn't the case for resume from ram on the host kernel. > > any ideas how to fix this? is it possible to intercept the resume from > ram and update the timekeeper->xtime_sec somehow? > or can the um arch somehow overwrite timespec_add_ns() to always use > div_u64_rem() instead? Hmm, does this always happen? At least on my notebook it did not happen. I've started an UML yesterday suspended it and after more than 12h it worked fine today. BTW: Do you see the issue also then freezing UML using the freezer cgroup? Would be easier to debug. :) -- Thanks, //richard -- 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/