On 22-1-2013 13:36, Yishin Li wrote: > 從我的 iPhone 傳送 > > Bas Laarhoven <[email protected]> 於 2013/1/22 下午8:07 寫道： > >> On 21-1-2013 22:20, Michael Haberler wrote: >>> Am 21.01.2013 um 20:10 schrieb Gilles Chanteperdrix: >>> >>>> On 01/21/2013 02:32 PM, Michael Haberler wrote: >>>> >>>>> Am 21.01.2013 um 12:56 schrieb Gilles Chanteperdrix: >>>>>>> question: does a RTC time warp have any possible bearing on >>>>>>> Xenomai operations? >>>>>> No, it should not, Xenomai uses its own clock, which is set only >>>>>> once upon boot, so, is unaffected by Linux wallclock time >>>>>> changes... or should be. >>>>> it might not be Xenomai after all. Uhum. >>>>> >>>>> the bughunt safari tribe has decided to focus on class 'duh' problems >>>>> and resolves to shut up until red hands are spotted. >>>> I would still put the check in the timer "set_next_event" callback, just >>>> in case... >>> I assume Bas will give the postmortem shortly - he nailed the issue; the >>> RTC boot timewarp makes for a lost DHCP lease midflight and NFS freezing, >>> making it look like a kernel hang. >>> >>> relieved, >>> >>> - Michael >> Michael said it all, there's not much for me to add. I'll summarize the >> case for the records ; ) >> >> Lesson learned: Change only one variable at a time and don't assume >> anything! >> >> I had been using a NFS mounted filesystem with the Beaglebone for over a >> year now without problems and got used to it's reliability (as I was >> used to in a corporate environment in the past). >> Because the Xenomai software was built with libraries (eabihf) not >> compatible with my (eabi) system I switched to the Ubuntu image Michael >> built, and everything seemed to work fine. Except that the (xenomai) >> kernel froze out after around 50-60 minutes of uptime. With the JTAG >> debugger I could see the kernel still running, but all applications >> (both text and X via SSH, and console via serial/USB connection) seemed >> frozen and there was no output indicating what was going on. Of course >> the xenomai kernel was the first suspect. But that proved to be a >> mistake. With hindsight, knowing the cause of the freeze now, I wonder >> why I haven't gotten the NFS connection time-out message on the console, >> but for some reason or another that isn't generated in this case. >> >> The underlying problem is that the Beaglebone has no battery backed >> real-time clock. This gives (only) a serious problem (freeze) with (1) a >> network mounted NFS root filesystem and (2) an initial kernel time lying >> in the past and (3) a DHCP lease time shorter than some multiple (in >> this case 2x) of the required system uptime. >> >> Ubuntu (and maybe Debian too) systems are obviously not designed to >> start with a completely wrong real-time clock value. And the dhclient >> (as many other programs) is not designed to handle the large time step >> that's generated once the clock is set properly sometime during the boot >> process. >> Note that if the filesystem is on local storage (e.g. FLASH or >> harddisk), there will only be a short disruption of the network >> connection and it's likely that the problem won't be noticed at all. >> >> A final solution hasn't been found yet: I prefer a workaround without >> changing the dhclient or some other standard program. I think it would >> suffice to acquire a new lease right after the time-step has been made. >> This has to be done without giving up the previous lease (that has >> expired because of the time-step), because that would cause the system >> to freeze again. Suggestions on how to do this are welcome. I can't >> spend much more time on this issue this week. >> >> -- Bas > How about using static IP for NFS mounted rootfs?
If you're not using DHCP this problem shouldn't affect you. -- Bas > > -Yishin > > ------------------------------------------------------------------------------ > Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, > MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current > with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft > MVPs and experts. ON SALE this month only -- learn more at: > http://p.sf.net/sfu/learnnow-d2d > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnnow-d2d _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
