[lxml-dev] Lxml Crash

[Alex Klizhentas]

OK, thanks for your suggestions - I'll apply changes immediately,
What about concurrency - XML trees are not shared between threads, so it's
unlikely a root cause.

On Wed, Mar 4, 2009 at 3:19 PM, Stefan Behnel <stefan_ml at behnel.de> wrote:

> Alex Klizhentas wrote:
> > sometimes i get exception killing apache process. It happens occasionally
> > (acually it happened once on my production site), so I have no more logs
> > up to the moment,
> > [...]
> > I will bring in more logs if crash repeats, but I will appreciate any
> > ideas/thoughts/comments so I can quickly eliminate/workaround/prevent the
> > issue from happening again.
>
> One thing to note is that you are using lxml 2.2alpha1. There were plenty
> of bugs that were fixed in 2.2 since then, including a couple of crash
> bugs. I'd try to switch to 2.2beta4 ASAP.
>
> http://codespeak.net/lxml/dev/changes-2.2beta4.html
>
>
> > I can only suspect that crash  happens when I am trying to
> > replace the node:
> >
> >     def replace(self,child,new_child):
> >         root = self.getroottree().getroot()
> >         index = self.index(child)
> >         if root._should_notify():
> >             old_child = deepcopy(child)
> >             self.insert(index,new_child)
> >             etree.ElementBase.remove(self,child)
> >             root._notify(NodeReplaced(old_child,new_child))
> >             return self[index]
> >         else:
> >             self.insert(index,new_child)
> >             etree.ElementBase.remove(self,child)
> >             return self[index]
>
> Regarding this code, I assume that "self" is an ElementBase subtype. I
> wonder why you didn't write it like this:
>
>    def replace(self,child,new_child):
>         etree.ElementBase.replace(self, child, new_child)
>        root = self.getroottree().getroot()
>        if root._should_notify():
>            root._notify(NodeReplaced(child, new_child))
>        return new_child
>
> BTW, is your tree protected against concurrent modification in any way? If
> your environment (mod_python?) is configured to run requests in parallel,
> concurrently replacing a child of the same parent may lead to crashes.
>
>
> > crash log is below:
> >
> > *** glibc detected *** /usr/sbin/apache2: free(): invalid pointer:
> > 0x08cd6eca ***
> > ======= Backtrace: =========
> > /lib/tls/i686/cmov/libc.so.6[0xb7e26a85]
> > /lib/tls/i686/cmov/libc.so.6(cfree+0x90)[0xb7e2a4f0]
> > /usr/lib/libxml2.so.2(xmlFreeNodeList+0x126)[0xa984d1e6]
> > /usr/lib/libxml2.so.2(xmlFreeNode+0x76)[0xa984d656]
> >
> /usr/lib/python2.5/site-packages/lxml-2.2alpha1-py2.5-linux-i686.egg/lxml/etree.so[0xa9992bf2]
> >
> /usr/lib/python2.5/site-packages/lxml-2.2alpha1-py2.5-linux-i686.egg/lxml/etree.so[0xa99b529f]
>
> All I can see here is that this happens when freeing a node or subtree.
> Not much I can extract from that.
>
> Stefan
>
>


-- 
Regards,
Alex
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