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Re: SVN repository possible race condition

From: Toby COllett <tcollett+lists_at_plan9.net.nz>
Date: Wed, 7 Jan 2009 14:57:48 +1300

I have finally had time to look into this further, and I can confirm that
the results are reproduceable outside subversion, I have attached a little
test application that triggers the same behaviour just if anyone is
interested. I am following up with the samba guys now, hopefully will have
some success there.

Just to answer the questions below:
Both samba server and client are linux.
Not related to server load as at nominally the same time 1.4 and 1.5 clients
are hitting the 1.4 server and only 1.5 has issues.


2008/10/3 John Szakmeister <john_at_szakmeister.net>

> After staring at this for a while I think I know what the issue is...
> although not technically Subversion's fault. Is your Samba share
> hosted on Windows by chance? What I believe is happening is that
> apr_dir_read() is returning the 'text-base' dir twice. Apparently
> some implementations of readdir() are broken when you delete entries.
> So on anything other than Windows, there is an attempt to rewind the
> directory. This causes text-base to show up again, and it's a
> directory when open() is called but has probably been removed by the
> time getdents() is called. So we've managed to hit a race condition.
> :-(
> Unfortunately, I'm not sure what the best solution is here. We
> already know that the entry we were trying to remove is a directory...
> so maybe the best answer is to check for that and skip the entry if
> the remove fails with ENOTDIR?
> FWIW, not much of this has changed since 1.4... have you upgraded
> whatever is hosting the share since then? Of course, if the workload
> of the server has picked up, it could be that you were "winning" the
> race and just not seeing the issue.
> -John

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Received on 2009-01-07 14:47:19 CET

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