Date: Mon, 19 Feb 2001 16:58:10 -0600 From: Mike Meyer <mwm@mired.org> To: stable@freebsd.org Subject: Lockups during periodic daily, take two... Message-ID: <14993.42242.471726.423046@guru.mired.org>
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Got it. My thanks to those who provided suggestions for getting into
DDB with this. It seems that XFree86-4 interferes with DDB in some
strange way, and I can't get into it *at all* if I've got X running,
changing VTs or not.
Anyway, it's a bug in fdesc. Analysis below. As verification, if I
unmount fdesc, the daily processing runs from crontab just fine. I
kind of like <(...), so I'd like fdesc back. Is devfs reasonablye
safe, and does it provide /dev/fd? If so, I'll turn that on. If not -
and no one who familiar with the code wants to try and fix it - I'll
take a whack at it.
<mike
The stack trace from ddb starts in the debugger, back through sc &
atkbd, thence through the interrupt (presumably from my invoking DDB
at the console). From there, it's:
fdesc_readdir+0xe6(<address>, <address>, 0, <address>, 4, 0)
getdirentries+0xf4(5 <addresses>)
Xint0x80_syscall+0x2b
According to gdb on the core dump, the fdesc_readdir is:
0xc019223e is in fdesc_readdir (../../miscfs/fdesc/fdesc_vnops.c:614).
609 while (i < sizeof(rootent) / sizeof(rootent[0]) &&
610 uio->uio_resid >= UIO_MX) {
611 dt = &rootent[i];
612 switch (dt->d_fileno) {
613 case FD_CTTY:
614 if (cttyvp(uio->uio_procp) == NULL)
615 continue;
616 break;
617
618 case FD_STDIN:
On the face of it, the while loop in fdesc_readdir is simply
broken. If you hit one of the continues in the loop (there are others
further down), you have missed anything in the loop that might change
either i or uip, meaning the loop doesn't terminate. It may be waiting
on other events to change it, but somehow I doubt it for the fdesc
code. Further, note that the code that is finding the continue in this
case is checking for a controlling terminal, which would explain the
difference in behavior between
In checking the CVS repository, I note that the last commit of this
code to a releng branch was december of 99, but the -current version
was worked on a a couple of weeks ago, and this while loop vanished
from the code in the first commit after that commit in december of 99.
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