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Diffstat (limited to 'open_issues/pfinet_vs_system_time_changes.mdwn')
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diff --git a/open_issues/pfinet_vs_system_time_changes.mdwn b/open_issues/pfinet_vs_system_time_changes.mdwn new file mode 100644 index 00000000..09b00d30 --- /dev/null +++ b/open_issues/pfinet_vs_system_time_changes.mdwn @@ -0,0 +1,101 @@ +[[!meta copyright="Copyright © 2010, 2011, 2012 Free Software Foundation, +Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag open_issue_hurd]] + + +# IRC, unknown channel, unknown date + + <grey_gandalf> I did a sudo date... + <grey_gandalf> and the machine hangs + +This was very likely a misdiagnosis. + + +# IRC, freenode, #hurd, 2011-03-25 + + <tschwinge> antrik: I suspect it'S some timing stuff in pfinet that perhaps + uses absolute time, and somehow wildely gets confused? + <antrik> tschwinge: BTW, pfinet doesn't actually die I think -- it just + drops open connections... + <antrik> perhaps it thinks they timed out + <tschwinge> antrik: Isn't the translator restarted instead? + <antrik> don't think so + <antrik> when pfinet actually dies, I also loose the NFS mounts, which + doesn't happen in this case + <antrik> hehe "... and the machine hangs" + <antrik> he didn't bother to check that the machine is perfectly fine, only + the SSH connection got dropped + <tschwinge> Ah, I see. So it'S perhaps indeed simply closes TCP + connections that have been without data for ``too long''? + <antrik> yeah, that's my guess + <antrik> my clock is speeding, so ntpdate sets it in the past + <antrik> perhaps there is some math that concludes the connection have been + inactive for -200 seconds, which (unsigned) is more than any timeout :-) + <tschwinge> (The other way round, you might likely get some integer + wrap-around, and thus the same result.) + <tschwinge> Yes. + + +# IRC, freenode, #hurd, 2011-10-26 + + <antrik> anyways, when ntpdate adjusts to the past, the connections hang, + roughly for the amount of time being adjusted + <antrik> they do not die though + <antrik> (well, if it's long enough, they probably timeout on the other + side...) + + +# IRC, freenode, #hurd, 2011-10-27 + + <antrik> oh, another interesting thing I observed is that the the subhurd + pfinet did *not* drop the connection... only the main Hurd one. I thought + the clock is system-wide?... + <tschwinge> It is. + <antrik> it's really fascinating that only the pfinet on the Hurd instance + where I set the date is affected, and not the pfinet in the other + instance + + +# IRC, freenode, #hurd, 2012-06-28 + + <bddebian> great, now setting the date/time fucked my machine + <pinotree> yes, we lack a monotonic clock + <pinotree> there are select() loops that use gettimeofday to determine how + much time to wait + <pinotree> thus if the time changes (eg goes back), the calculation goes + crazy + <antrik> pinotree: didn't you implement a monotonic clock?... + <pinotree> started to + <antrik> bddebian: did it really fuck the machine? normally it only resets + TCP connections... + <pinotree> yeah, i remember such gettimeofay-based select-loops at least in + pfinet + <antrik> I don't think it's a loop. it just drops the connections, + believing they have timed out + <bddebian> antrik: Well in this case I don't know because I am at work but + it fucked me because I now cannot get to it.. :) + <antrik> bddebian: that's odd... you should be able to just log in again + IIRC + + +# IRC, freenode, #hurd, 2012-07-29 + + <antrik> pfinet can't cope with larger system time changes because it can't + use a monotonic clock + +[[clock_gettime]]. + + <braunr> well when librt becomes easily usable everywhere (it it's + possible), it will be quite easy to work around this issue + <pinotree> yes and no, you just need a monotonic clock and clock_gettime + able to use it + <braunr> why "no" ? |