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Re: bin/27179 (dump(8) goes into loop, never finishing dump)
The following reply was made to PR bin/27179; it has been noted by GNATS.
From: David Holland <dholland-bugs%netbsd.org@localhost>
Subject: Re: bin/27179 (dump(8) goes into loop, never finishing dump)
Date: Mon, 3 May 2010 02:46:31 +0000
On Mon, May 03, 2010 at 01:26:40AM +0000, dholland%NetBSD.org@localhost wrote:
> I see nothing in the changelogs for dump that would have been remotely
> likely to correct this. All the same, it would be extremely useful to
> know if this problem has been seen recently.
Looking into it some more I have the following observations:
(1) it is probably a race condition somewhere, so there's some more or
less fixed probability of triggering it at any given moment, which is
why it manifests mostly on large dumps;
(2) in the case cited, it is making progress, or thinks it is, just at
about 1/100th the normal rate;
(3) the scheme dump uses to coordinate its subprocesses is fragile and
could be messed up by all manner of kernel bugs, particularly in
signals or AF_UNIX sockets; however, I also can't so far rule out a
corner case in the state transitions;
(4) however, all of the likely issues I can think of (of either kind)
would lead to it hanging completely, not proceeding at a crawl.
(5) I also have no idea why it would be correlated with using amanda.
So I dunno. If anyone manages to reproduce this it would be useful to
know where the various dump processes are spending their time while
mostly not making progress...
David A. Holland
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