IDEA-161261 LowMemoryWatcher sporadically fails with ConcurrentModificationException

platform/util/src/com/intellij/openapi/util/LowMemoryWatcher.java

@@ -21,8 +21,6 @@ import com.intellij.util.containers.WeakList;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.List;
-
 /**
  * @author Eugene Zhuravlev
  *         Date: Aug 24, 2010
@@ -30,12 +28,12 @@ import java.util.List;
 public class LowMemoryWatcher {
   private static final Logger LOG = Logger.getInstance("#com.intellij.openapi.util.LowMemoryWatcher");
 
-  private static final List<Runnable> ourListeners = new WeakList<Runnable>();
+  private static final WeakList<Runnable> ourListeners = new WeakList<Runnable>();
   private final Runnable myRunnable;
 
   static void onLowMemorySignalReceived() {
     LOG.info("Low memory signal received.");
-    for (Runnable watcher : ourListeners) {
+    for (Runnable watcher : ourListeners.toStrongList()) {
       try {
         watcher.run();
       }

platform/util/src/com/intellij/openapi/util/LowMemoryWatcherManager.java

@@ -31,6 +31,7 @@ import java.lang.management.MemoryPoolMXBean;
 import java.lang.management.MemoryType;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 public class LowMemoryWatcherManager implements Disposable {
   private static final Logger LOG = Logger.getInstance("#com.intellij.openapi.util.LowMemoryWatcherManager");
@@ -38,6 +39,7 @@ public class LowMemoryWatcherManager implements Disposable {
   private static final long MEM_THRESHOLD = 5 /*MB*/ * 1024 * 1024;
 
   private Future<?> mySubmitted; // guarded by ourJanitor
+  private final AtomicBoolean myProcessing = new AtomicBoolean();
   private final Runnable myJanitor = new Runnable() {
     @Override
     public void run() {
@@ -75,7 +77,7 @@ public class LowMemoryWatcherManager implements Disposable {
       if (MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED.equals(notification.getType()) ||
           MemoryNotificationInfo.MEMORY_COLLECTION_THRESHOLD_EXCEEDED.equals(notification.getType())) {
         if (Registry.is("low.memory.watcher.sync", true)) {
-          myJanitor.run();
+          handleEventImmediately();
           return;
         }
 
@@ -87,6 +89,18 @@ public class LowMemoryWatcherManager implements Disposable {
       }
     }
   };
+
+  private void handleEventImmediately() {
+    if (myProcessing.compareAndSet(false, true)) {
+      try {
+        myJanitor.run();
+      }
+      finally {
+        myProcessing.set(false);
+      }
+    }
+  }
+
   private final NotNullLazyValue<ExecutorService> myExecutor = new NotNullLazyValue<ExecutorService>() {
     @NotNull
     @Override