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

Reviewed-by: stefank, ayang, tschatzl

Author: fisk

test/hotspot/jtreg/ProblemList-Xcomp.txt

@@ -40,6 +40,4 @@ serviceability/sa/TestJhsdbJstackMixed.java 8248675 linux-aarch64
 
 serviceability/jvmti/VMObjectAlloc/VMObjectAllocTest.java 8307462 generic-all
 
-gc/cslocker/TestCSLocker.java 8293289 generic-x64
-
 serviceability/sa/ClhsdbInspect.java 8283578 windows-x64

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

@@ -48,10 +48,13 @@ 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);
         }