Changeset 8020 in vbox for trunk/src/VBox/Main/xml

Timestamp:

Apr 16, 2008 10:14:39 AM (17 years ago)

Author:

vboxsync

Message:

Main/Settigs: Disabled File (..., RTFILE aHandle, ...) constructor since it is not thread-safe when the handle is shared across different File instances (needs a handle duplicate operation in the IPRT File API).

File:

• trunk/src/VBox/Main/xml/Settings.cpp (modified) (5 diffs)

trunk/src/VBox/Main/xml/Settings.cpp

@@ -21 +21 @@
 #include <iprt/err.h>
 #include <iprt/file.h>
+#include <iprt/lock.h>
 
 #include <libxml/tree.h>
@@ -74 +75 @@
     {
         xmlExternalEntityLoader defaultEntityLoader;
+
+        /** Used to provide some thread safety missing in libxml2 (see e.g.
+         *  XmlTreeBackend::read()) */
+        RTLockMtx lock;
     }
     xml;
@@ -382 +387 @@
 }
 
-File::File (Mode aMode, RTFILE aHandle, const char *aFileName /* = NULL */ )
+#if 0
+/// @todo disabled until made thread-safe by using handle duplicates
+File::File (Mode aMode, RTFILE aHandle, const char *aFileName)
     : m (new Data())
 {
@@ -400 +407 @@
     setPos (0);
 }
+#endif
 
 File::~File()
@@ -903 +911 @@
     m->trappedErr.reset();
 
-    /* Set up the external entity resolver. Note that we do it in a
-     * thread-unsafe fashion because this stuff is not thread-safe in libxml2.
-     * Making it thread-safe would require a) guarding this method with a
-     * mutex and b) requiring our API caller not to use libxml2 on some other
-     * thread (which is not practically possible). So, our API is not
-     * thread-safe for now (note that there are more thread-unsafe assumptions
-     * below like xsltGenericError which is also a libxslt limitation).*/
+    /* We use the global lock for the whole duration of this method to serialize
+     * access to thread-unsafe xmlGetExternalEntityLoader() and some other
+     * calls. It means that only one thread is able to parse an XML stream at a
+     * time but another choice would be to patch libxml2/libxslt which is
+     * unwanted now for several reasons. Search for "thread-safe" to find all
+     * unsafe cases. */
+    RTLock alock (gGlobal.xml.lock);
+
     xmlExternalEntityLoader oldEntityLoader = xmlGetExternalEntityLoader();
     sThat = this;