On Fri, 15 Nov 1996, Wolfgang Solfrank wrote:

> There is nothing wrong with doing an 'ls' while copying a file to
> the same directory.  If this results in a deadlock, there is a bug
> somewhere.  If you can reproduce this with a more current system,
> I'm sure we'd all like to hear it (probably "like" is not the
> correct word here :-)).

It's extremely reproducible if you use union mounts.  I keep the
NetBSD-current source distribution unchanged in one directory tree,
and union mount another one on top, where my changes end up.  A cron
job generates diffs every night (the two trees are actually mounted,
one after the other, on /usr/src, so they can be diffed where they
actually reside).  This works great, as long as I remember that only
one process can do work inside the union mount under /usr/src at any
given time: if I make the mistake of trying to make changes there
while I've got a kernel compile or something going in the background,
it only takes a very short time before the file system deadlocks.
When this happens, everything works just fine, except that any access
to the (real) file systems involved will hang.

-tih
-- 
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