From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1Jry9e-0006FR-9v for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 May 2008 09:30:38 -0700 Received: from [198.99.130.12] (helo=saraswathi.solana.com) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1Jry9b-0007H1-Nw for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 May 2008 09:30:38 -0700 Date: Fri, 2 May 2008 12:30:20 -0400 From: Jeff Dike Message-ID: <20080502163020.GB7843@c2.user-mode-linux.org> References: <877iel7ljp.fsf@hades.wkstn.nix> <87ve256146.fsf@hades.wkstn.nix> <871w4sqxgv.fsf@hades.wkstn.nix> <20080428164443.GB9628@c2.user-mode-linux.org> <871w4n9fo8.fsf@hades.wkstn.nix> <20080501151351.GA6303@c2.user-mode-linux.org> <87prs57g4h.fsf@hades.wkstn.nix> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87prs57g4h.fsf@hades.wkstn.nix> Subject: Re: [uml-devel] actually useful backtrace from a CPU-chewing hang List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: Nix Cc: user-mode-linux-devel@lists.sourceforge.net On Fri, May 02, 2008 at 12:34:54AM +0100, Nix wrote: > loki:/tmp# /usr/bin/ntpdate -bv hades > 30 Apr 22:45:52 ntpdate[8833]: ntpdate 4.2.4p4@1.1520-o Fri Feb 22 18:37:11 UTC 2008 (1) > 30 Apr 22:45:52 ntpdate[8833]: step time server 192.168.14.18 offset -5.728539 sec > > so in effect yes :) > > Hm. A five-second skip forwards via date --set works fine. A five-second > skip *backwards*, and instant boom. I tried both directions for the hell of it. With your config, I'm seeing a hang until the system time catches up to what UML thought it should have been in the first place. But it's only a few seconds, not forever. However, stracing it did reveal a bogus interval trying to be set, which the patch below fixes. It doesn't cause any behavior change here, so YMMV. This includes the previous patch, which I think is a good idea anyway, so back that out and drop this in its place. Jeff Index: linux-2.6.22/arch/um/os-Linux/time.c =================================================================== --- linux-2.6.22.orig/arch/um/os-Linux/time.c 2008-04-24 13:21:28.000000000 -0400 +++ linux-2.6.22/arch/um/os-Linux/time.c 2008-05-02 12:21:01.000000000 -0400 @@ -107,6 +107,10 @@ static void deliver_alarm(void) unsigned long long this_tick = os_nsecs(); int one_tick = UM_NSEC_PER_SEC / UM_HZ; + /* Protection against the host's time going backwards */ + if ((last_tick != 0) && (this_tick < last_tick)) + this_tick = last_tick; + if (last_tick == 0) last_tick = this_tick - one_tick; @@ -149,6 +153,9 @@ static int after_sleep_interval(struct t start_usecs = usec; start_usecs -= skew / UM_NSEC_PER_USEC; + if (start_usecs < 0) + start_usecs = 0; + tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC, .tv_usec = start_usecs % UM_USEC_PER_SEC }); interval = ((struct itimerval) { { 0, usec }, tv }); -- Work email - jdike at linux dot intel dot com ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel