On Thu, 8 Apr 2021 06:58:14 GMT, Matthias Bläsing
<github.com+2179736+matthiasblaes...@openjdk.org> wrote:
> The functions from FileSystemJava are called from different threads the
> root problem manifests because the JNI FindClass function behaves
> differently when called from a context that is the ancestor of a java
> frame compared to when called in isolation.
>
> A segmentation fault is observed when local storage of a webview is
> accessed. At that time a new native thread is spun up and that sets up
> the local storage, by calling into the JVM via
> WTF::FileSystem::makeAllDirectories. At that point GetFileSystemClass is
> invoked to get a referenc to the java implementation of the FileSystem.
> As this is is called from a new native thread (no java context
> available), JNI uses the system classloader to locate the class. This
> fails if the JavaFX modules are not on the boot module/class path.
>
> Instead on relying on fetching the class reference everytime it is
> needed, this change fetches it once when the JavaFX library is loaded
> and stores it in the WTF namespace.
>
> In addition to this it was observed, that there is no attachment to the
> JVM done when calling into the filesystem. No fault was observed, but
> the JNI specs indicate, that the JNIEnv interface is only valid when
> attached.
The fix looks OK to me, although I'd like @arun-Joseph to comfirm.
The test needs one change in how the resource (the `.html` file) is located,
and I added a couple minor comments on the test. I'll test it after that.
modules/javafx.web/src/main/native/Source/WTF/wtf/java/FileSystemJava.cpp line
249:
> 247: if (isHandleValid(handle)) {
> 248: AttachThreadAsDaemonToJavaEnv autoAttach;
> 249: JNIEnv* env = autoAttach.env();
Minor: indentation
modules/javafx.web/src/main/native/Source/WTF/wtf/java/JavaEnv.cpp line 144:
> 142: // the right one
> 143: static JGClass
> fileSystemRef(env->FindClass("com/sun/webkit/FileSystem"));
> 144: WTF::comSunWebkitFileSystem = fileSystemRef;
Can you `ASSERT` that the returned class is not null?
tests/system/src/testapp7/java/mymod/myapp7/LocalStorageAccessWithModuleLayer.java
line 81:
> 79: webview.getEngine().getLoadWorker().stateProperty().addListener(
> 80: new ChangeListener<State>() {
> 81: public void changed(ObservableValue ov, State
> oldState, State newState) {
Suggestion: maybe use a lambda here to make the code more compact? (it's up to
you whether to change it)
tests/system/src/testapp7/java/mymod/myapp7/LocalStorageAccessWithModuleLayer.java
line 92:
> 90: }
> 91: });
> 92:
> webview.getEngine().load(LocalStorageAccessWithModuleLayer.class.getResource("/LocalStorageAccess.html").toExternalForm());
This fails to find the resource when I run the test via gradle. I recommend
putting it in the same package as the class and removing the leading `/` (e.g.,
see the FXML resources in `testapp6` or `testscriptapp1`).
tests/system/src/testapp7/java/mymod/myapp7/LocalStorageAccessWithModuleLayerLauncher.java
line 64:
> 62: // Hack to get the classes of this programm into a module layer
> 63: List<Path> modulePaths = new ArrayList<>();
> 64: for(String workerPath:
> System.getProperty("module.path").split(File.pathSeparator)) {
Minor: missing space after the `for` and also before the `:`
-------------
PR: https://git.openjdk.java.net/jfx/pull/458
