Re: [xml] IO callbacks are not thread-safe

[Daniel Veillard <veillard redhat com>]

On Thu, Mar 26, 2009 at 07:06:14PM +0100, Nick Wellnhofer wrote:
> 
> The input and output callbacks of libxml are stored in static arrays in
> xmlIO.c, so any use of the callback functions is not thread-safe.
> 
> In many cases this shouldn't be a problem, if callbacks are registered
> only at the start of a program. But the Perl bindings register and
> unregister callbacks every time a document is parsed. I can reproduce

  Uhhhh ????
That sounds severely broken to me. Can you details why, and how ?

> random segfaults or other errors when processing many thousand documents
> in concurrent threads with the libxml Perl bindings.
> 
> I'm willing to help fix this, but I'm not sure about the correct
> approach. Should the callback arrays be added to the global variables in
> globals.c?

Those variables are not public, so I guess a different way would be
preferable. Still I can't see any good valid reason to change the values
all the time. Something is severely broken there in the perl bindings !
If they need a per parsing instance processing they should use the data
block provided by the I/O to make the switch, but register an unified
routine for all threads. No really this doesn't make any sense to me,
but maybe you can come up with a valid reason,

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/