kern/104406: [ufs] Processes get stuck in "ufs" state underpersistent CPU load

[Oleg Derevenetz]

> > > Can anyone take a look on PR kern/104406 ? I got repeatable hang
situation,
> > > but I can't obtain a kernel dump to get result of all show commands
from
> > > here:
> > >
> > >
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html
> > >
> > > After my break to debugger using Ctrl+Alt+Esc sequence and entering a
> > > "panic" command kernel does not wrote a kernel dump but seems to hang.
Can
> > > anyone describe how to obtain a kernel dump in this situation, or at
least
> > > say - which output of show commands need in first place to debug this
?
> > > Output of all suggested commands is huge and I afraid of making
mistake
> > > when carrying this output from screen to list of paper and back :-)
>
> This very easy to reproduce [ufs] uninterruptable deadlock
> for both of RELENG_6 and RELENG_7. Look at this PR:
> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/107439
>
> The PR is closed but the problem is still here with 7.0-PRERELEASE
> and, perhaps, CURRENT.

This is probably another bug because:

1. I built kernel with INVARIANTS as described in on "Debugging Deadlocks"
page of FreeBSD Developers' Handbook and got no panic, but only deadlock;
2. I have no NTFS filesystem at all and just do a copy of file(s) from FTP
to local UFS using mc. In this PR panic occured when NTFS mounted r/w (and
NOT occured when the same NTFS mounted r/o).

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Oleg Derevenetz <oleg at vsi.ru> OOD3-RIPE
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