Avoid deadlocks

h2/src/main/org/h2/command/Command.java

@@ -251,13 +251,14 @@ public abstract class Command implements CommandInterface {
         if (e.getErrorCode() != ErrorCode.CONCURRENT_UPDATE_1) {
             throw e;
         }
-        long now = System.currentTimeMillis();
+        long now = System.nanoTime() / 1000000;
         if (start != 0 && now - start > session.getLockTimeout()) {
             throw DbException.get(ErrorCode.LOCK_TIMEOUT_1, e.getCause(), "");
         }
-        try {
         Database database = session.getDatabase();
         int sleep = 1 + MathUtils.randomInt(10);
+        while (true) {
+            try {
                 if (database.isMultiThreaded()) {
                     Thread.sleep(sleep);
                 } else {
@@ -266,6 +267,11 @@ public abstract class Command implements CommandInterface {
             } catch (InterruptedException e1) {
                 // ignore
             }
+            long slept = System.nanoTime() / 1000000 - now;
+            if (slept >= sleep) {
+                break;
+            }
+        }
         return start == 0 ? now : start;
     }