Date: 21 Feb 2001 23:15:26 -0000 From: mwm@mired.org To: FreeBSD-gnats-submit@freebsd.org Subject: kern/25266: fdesc file system in -STABLE locks up during nightly builds Message-ID: <20010221231526.16434.qmail@guru.mired.org>
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>Number: 25266
>Category: kern
>Synopsis: fdesc file system in -STABLE locks up during nightly builds
>Confidential: no
>Severity: serious
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Feb 21 15:20:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator: Mike Meyer
>Release: FreeBSD 4.2-STABLE i386
>Organization:
Meyer Consulting
>Environment:
fdesc in use on a 4.2-STABLE system, and daily_clean_disks_enable set
to yes in /etc/periodic.conf This lockup only happens if periodic is
run from cron; running it from the command line will not cause a
problem.
>Description:
The system locks up every night a few seconds into the daily periodic
run.
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 running periodic from cron vs from the
command line.
>How-To-Repeat:
set daily_clean_disks_enable to YES in /etc/make.conf on a 4.2 box,
mount fdesc, and watch it lock up.
>Fix:
It's not clear how to fix the code. I note that the last MFC of this
code is over a year old, and the very next commit simply removed this
code. Possibly MFC'ing a more recent version would solve the problem.
>Release-Note:
>Audit-Trail:
>Unformatted:
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