Re: [xml] [PATCH] Fix xsltExtModuleFunctionLookup() / xsltExtModuleRegisterDynamic() deadlock.

[Daniel Veillard <veillard redhat com>]

On Mon, Sep 07, 2009 at 10:50:42PM +0100, Nix wrote:
> Fix a deadlock when encountering extensions that do not exist on the supported platform at
> all. Both xsltExtModuleFunctionLookup() and xsltExtModuleRegisterDynamic() take the
> xsltExtMutex, but the former calls the latter -> deadlock.
>
> Dropping the mutex and taking it again is safe, as xsltExtModuleRegisterDynamic() checks that
> it has not already been called for a particular module. So do that.

  Ah right, that's my fault, I added mutex access to allow concurent
access but I didn't realize the deadlock. The code is in git but not
released yet, so hopefully the problem is limited :-)

> diff --git a/libxslt/extensions.c b/libxslt/extensions.c
> index 3b99de8..a797c39 100644
> --- a/libxslt/extensions.c
> +++ b/libxslt/extensions.c
> @@ -1424,6 +1424,8 @@ xsltExtModuleFunctionLookup(const xmlChar * name, const xmlChar * URI)
>  
>      XML_CAST_FPTR(ret) = xmlHashLookup2(xsltFunctionsHash, name, URI);
>  
> +    xmlMutexUnlock(xsltExtMutex);
> +
>      /* if lookup fails, attempt a dynamic load on supported platforms */
>      if (NULL == ret) {
>          if (!xsltExtModuleRegisterDynamic(URI)) {
> @@ -1432,8 +1434,6 @@ xsltExtModuleFunctionLookup(const xmlChar * name, const xmlChar * URI)

Good patch but the mutext should be taken/released again around the second
Lookup.
>          }
>      }
>  
> -    xmlMutexUnlock(xsltExtMutex);
> -
>      return ret;
>  }
>  

  Applied and commited to Git, please double check if you have a chance,

   thanks again !

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/