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Fix race condition in LanguageServerWrapper resulting in NullPointerException during LS initialization #985

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merged 3 commits into from
May 8, 2024
Merged

Fix race condition in LanguageServerWrapper resulting in NullPointerException during LS initialization #985

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e6ea1b7
Fix race condition resulting in NullPointerException
sebthom May 3, 2024
a58a823
improve method name advanceInitializeFutureMonitor
sebthom May 7, 2024
02fce99
use UncheckedIOException
sebthom May 7, 2024
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29 changes: 16 additions & 13 deletions org.eclipse.lsp4e/src/org/eclipse/lsp4e/LanguageServerWrapper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@

import java.io.File;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.HashMap;
Expand Down Expand Up @@ -157,7 +158,7 @@ public void dirtyStateChanged(IFileBuffer buffer, boolean isDirty) {
protected StreamConnectionProvider lspStreamProvider;
private Future<?> launcherFuture;
private CompletableFuture<Void> initializeFuture;
private IProgressMonitor initializeFutureMonitor;
private final AtomicReference<IProgressMonitor> initializeFutureMonitorRef = new AtomicReference<>();
private final int initializeFutureNumberOfStages = 7;
private LanguageServer languageServer;
private LanguageClientImpl languageClient;
Expand Down Expand Up @@ -286,7 +287,7 @@ private synchronized void start(boolean forceRestart) throws IOException {
final Job job = createInitializeLanguageServerJob();
this.launcherFuture = new CompletableFuture<>();
this.initializeFuture = CompletableFuture.supplyAsync(() -> {
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
if (LoggingStreamConnectionProviderProxy.shouldLog(serverDefinition.id)) {
this.lspStreamProvider = new LoggingStreamConnectionProviderProxy(
serverDefinition.createConnectionProvider(), serverDefinition.id);
Expand All @@ -297,11 +298,11 @@ private synchronized void start(boolean forceRestart) throws IOException {
try {
lspStreamProvider.start();
} catch (IOException e) {
throw new RuntimeException(e);
throw new UncheckedIOException(e);
}
return null;
}).thenRun(() -> {
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
languageClient = serverDefinition.createLanguageClient();

initParams.setProcessId((int) ProcessHandle.current().pid());
Expand Down Expand Up @@ -333,18 +334,18 @@ private synchronized void start(boolean forceRestart) throws IOException {
this.launcherFuture = launcher.startListening();
})
.thenCompose(unused -> {
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
return initServer(rootURI);
})
.thenAccept(res -> {
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
serverCapabilities = res.getCapabilities();
this.initiallySupportsWorkspaceFolders = supportsWorkspaceFolders(serverCapabilities);
}).thenRun(() -> {
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
this.languageServer.initialized(new InitializedParams());
}).thenRun(() -> {
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
final Map<URI, IDocument> toReconnect = filesToReconnect;
initializeFuture.thenRunAsync(() -> {
watchProjects();
Expand All @@ -357,7 +358,7 @@ private synchronized void start(boolean forceRestart) throws IOException {
}
});
FileBuffers.getTextFileBufferManager().addFileBufferListener(fileBufferListener);
advanceinitializeFutureMonitor();
advanceInitializeFutureMonitor();
}).exceptionally(e -> {
stop();
final Throwable cause = e.getCause();
Expand All @@ -378,7 +379,8 @@ private synchronized void start(boolean forceRestart) throws IOException {
}
}

private void advanceinitializeFutureMonitor() {
private void advanceInitializeFutureMonitor() {
final var initializeFutureMonitor = initializeFutureMonitorRef.get();
if (initializeFutureMonitor != null) {
if (initializeFutureMonitor.isCanceled()) {
throw new CancellationException();
Expand All @@ -387,11 +389,12 @@ private void advanceinitializeFutureMonitor() {
}
}

private synchronized Job createInitializeLanguageServerJob() {
private Job createInitializeLanguageServerJob() {
return new Job(NLS.bind(Messages.initializeLanguageServer_job, serverDefinition.label)) {
@Override
protected IStatus run(IProgressMonitor monitor) {
initializeFutureMonitor = SubMonitor.convert(monitor, initializeFutureNumberOfStages);
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Maybe it is a silly question, but do we need an AtomicReference? Could we not achieve the same by saving initializeFutureMonitor to a local variable in line 394 (and also on line 382) before saving it to the class field, and then mark the monitor as done using the local variable?

Is there a benefit of AtomicReference over the local variable?

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@sebthom sebthom May 8, 2024 •
edited
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As far as I see it, at a minimum the initializeFutureMonitor needs to be made volatile because it is accessed from two different threads and the Job in createInitializeLanguageServerJob otherwise may never see the assigned value. The nice part of AtomicReference is that it offers compareAndSet() which can avoid another type of race conditions when the wrapper is stopped and restarted in quick succession. Also I find working with AtomicReference is more expressive regarding the intention than dealing with a volatile field.

final var initializeFutureMonitor = SubMonitor.convert(monitor, initializeFutureNumberOfStages);
initializeFutureMonitorRef.set(initializeFutureMonitor);
CompletableFuture<Void> currentInitializeFuture = initializeFuture;
try {
if (currentInitializeFuture != null) {
Expand All @@ -405,7 +408,7 @@ protected IStatus run(IProgressMonitor monitor) {
}
} finally {
initializeFutureMonitor.done();
initializeFutureMonitor = null;
initializeFutureMonitorRef.compareAndSet(initializeFutureMonitor, null);
}
return Status.OK_STATUS;
}
Expand Down