8308043: Deadlock in TestCSLocker.java due to blocking GC while allocating

Reviewed-by: mbaesken
Backport-of: 285c833ffacdaabe7c4955cbbafb3bc459d26784

Author: Amos Shi

test/hotspot/jtreg/gc/cslocker/TestCSLocker.java

@@ -46,10 +46,13 @@ public static void main(String args[]) throws Exception {
         // start CS locker thread
         CSLocker csLocker = new CSLocker();
         csLocker.start();
+        // After the CSLocker thread has started, any operation such as an allocation,
+        // which could rely on the GC to make progress, will cause a deadlock that will
+        // make the test time out. That includes printing. Please don't use any such
+        // code until unlock() is called below.
 
         // check timeout to success deadlocking
-        while(System.currentTimeMillis() < startTime + timeout) {
-            System.out.println("sleeping...");
+        while (System.currentTimeMillis() < startTime + timeout) {
             sleep(1000);
         }