[libxslt] Fix a mutex deadlock on unregistered extensions

[Daniel Veillard <veillard src gnome org>]

commit 8619ab630e705805cafa4ba24c94b6c1311d0e01
Author: Nix <nix esperi org uk>
Date:   Tue Sep 8 10:22:13 2009 +0200

    Fix a mutex deadlock on unregistered extensions
    
    * libxslt/extensions.c: both xsltExtModuleFunctionLookup() and
      xsltExtModuleRegisterDynamic() take the xsltExtMutex, but the
      former calls the latter

 libxslt/extensions.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/libxslt/extensions.c b/libxslt/extensions.c
index 3b99de8..ebb81f5 100644
--- a/libxslt/extensions.c
+++ b/libxslt/extensions.c
@@ -1424,16 +1424,20 @@ 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)) {
+            xmlMutexLock(xsltExtMutex);
+
             XML_CAST_FPTR(ret) =
                 xmlHashLookup2(xsltFunctionsHash, name, URI);
+
+            xmlMutexUnlock(xsltExtMutex);
         }
     }
 
-    xmlMutexUnlock(xsltExtMutex);
-
     return ret;
 }