Prevent repeated initialization of "net" library.

Author: peter-hofer

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/NativeLibrarySupport.java

@@ -141,7 +141,7 @@ private boolean loadLibrary0(File file, boolean asBuiltin) {
         return addLibrary(asBuiltin, canonical, true);
     }
 
-    private boolean addLibrary(boolean asBuiltin, String canonical, boolean loadAndInitialize) {
+    private boolean addLibrary(boolean asBuiltin, String canonical, boolean initialize) {
         lock.lock();
         try {
             NativeLibrary lib = null;
@@ -171,19 +171,22 @@ private boolean addLibrary(boolean asBuiltin, String canonical, boolean loadAndI
                 lib = PlatformNativeLibrarySupport.singleton().createLibrary(canonical, asBuiltin);
                 created = true;
             }
-            if (loadAndInitialize) {
-                currentLoadContext.push(lib);
-                try {
-                    if (!lib.load()) {
-                        return false;
-                    }
-                    if (libraryInitializer != null) {
-                        libraryInitializer.initialize(lib);
-                    }
-                } finally {
-                    NativeLibrary top = currentLoadContext.pop();
-                    assert top == lib;
+            currentLoadContext.push(lib);
+            try {
+                if (!lib.load()) {
+                    return false;
+                }
+                /*
+                 * Initialization of a library must be skipped if it can be initialized at most once
+                 * per process and another isolate has already initialized it. However, the library
+                 * must be (marked as) loaded above so it cannot be loaded and initialized later.
+                 */
+                if (initialize && libraryInitializer != null) {
+                    libraryInitializer.initialize(lib);
                 }
+            } finally {
+                NativeLibrary top = currentLoadContext.pop();
+                assert top == lib;
             }
             if (created) {
                 knownLibraries.add(lib);
@@ -210,6 +213,7 @@ public PointerBase findSymbol(String name) {
     }
 
     public void registerInitializedBuiltinLibrary(String name) {
-        addLibrary(true, name, false);
+        boolean success = addLibrary(true, name, false);
+        assert success;
     }
 }