Add logging around the message processing lock.

app/src/main/java/org/thoughtcrime/securesms/crypto/DatabaseSessionLock.java

@@ -13,6 +13,10 @@ public enum DatabaseSessionLock implements SignalSessionLock {
 
   INSTANCE;
 
+  public static final long NO_OWNER = -1;
+
+  private volatile long ownerThreadId = NO_OWNER;
+
   @Override
   public Lock acquire() {
     SQLiteDatabase db = DatabaseFactory.getInstance(ApplicationDependencies.getApplication()).getRawDatabase();
@@ -23,9 +27,34 @@ public enum DatabaseSessionLock implements SignalSessionLock {
 
     db.beginTransaction();
 
+    ownerThreadId = Thread.currentThread().getId();
+
     return () -> {
+      ownerThreadId = -1;
       db.setTransactionSuccessful();
       db.endTransaction();
     };
   }
+
+  /**
+   * Important: Only truly useful for debugging. Do not rely on this for functionality. There's tiny
+   * windows where this state might not be fully accurate.
+   *
+   * @return True if it's likely that some other thread owns this lock, and it's not you.
+   */
+  public boolean isLikelyHeldByOtherThread() {
+    long ownerThreadId = this.ownerThreadId;
+    return ownerThreadId != -1 && ownerThreadId == Thread.currentThread().getId();
+  }
+
+  /**
+   * Important: Only truly useful for debugging. Do not rely on this for functionality. There's a
+   * tiny window where a thread may still own the lock, but the state we track around it has been
+   * cleared.
+   *
+   * @return The ID of the thread that likely owns this lock, or {@link #NO_OWNER} if no one owns it.
+   */
+  public long getLikeyOwnerThreadId() {
+    return ownerThreadId;
+  }
 }

app/src/main/java/org/thoughtcrime/securesms/messages/IncomingMessageProcessor.java

@@ -113,7 +113,14 @@ public class IncomingMessageProcessor {
 
       stopwatch.split("queue-check");
 
+      long ownerThreadId = DatabaseSessionLock.INSTANCE.getLikeyOwnerThreadId();
+      if (ownerThreadId != DatabaseSessionLock.NO_OWNER && ownerThreadId != Thread.currentThread().getId()) {
+        Log.i(TAG, "It is likely that some other thread has this lock. Owner: " + ownerThreadId + ", Us: " + Thread.currentThread().getId());
+      }
+
       try (SignalSessionLock.Lock unused = DatabaseSessionLock.INSTANCE.acquire()) {
+        Log.i(TAG, "Acquired lock while processing message " + envelope.getTimestamp() + ".");
+
         DecryptionResult result = MessageDecryptionUtil.decrypt(context, envelope);
         stopwatch.split("decrypt");