RFR 8251118: BiasedLocking::preserve_marks should not have a HandleMark

[Patricio Chilano]

Hi Harold,

Thanks for looking at this.

On 8/11/20 4:11 PM, Harold Seigel wrote:
> Hi Patricio,
>
> The fix looks good.  Could you also add a test based on the failure 
> discussed in the bug description?
Sure. From the mach5 job I run without the patch I see that 
test/hotspot/jtreg/gc/TestFullGCALot.java fails pretty much consistently 
on all platforms and tiers 1-3. What do you think about adding a new run 
on that test with -XX:+UseBiasedLocking? Change would be:

diff --git a/test/hotspot/jtreg/gc/TestFullGCALot.java 
b/test/hotspot/jtreg/gc/TestFullGCALot.java
--- a/test/hotspot/jtreg/gc/TestFullGCALot.java
+++ b/test/hotspot/jtreg/gc/TestFullGCALot.java
@@ -26,8 +26,9 @@
  /*
   * @test TestFullGCALot
- * @bug 4187687 8187819
+ * @bug 4187687 8187819 8251118
   * @summary Ensure no access violation when using FullGCALot
   * @requires vm.debug
   * @run main/othervm -XX:NewSize=10m -XX:+FullGCALot 
-XX:FullGCALotInterval=120 gc.TestFullGCALot
+ * @run main/othervm -XX:NewSize=10m -XX:+FullGCALot 
-XX:FullGCALotInterval=120 -XX:+UseBiasedLocking gc.TestFullGCALot
   */

I would suggest adding a new run to FieldMonitor.java with 
-XX:+UseBiasedLocking instead, but it doesn't fail as consistently.

Alternatively a new test would be pretty much like TestFullGCALot.java. 
The only change I would make is to explicitly add a synchronized statement:

/*
  * @test TestFullGCOnSync
  * @bug 8251118
  * @run main/othervm -XX:NewSize=10m -XX:+FullGCALot 
-XX:FullGCALotInterval=120 -XX:+UseBiasedLocking TestFullGCOnSync
  */

public class TestFullGCOnSync {
   public static void main(String args[]) throws Exception {
     Integer x = new Integer(10);
     synchronized (x) {
       System.gc();
       System.out.println("Hello world!");
     }
   }
}

Thanks,
Patricio
> Thanks, Harold
>
> On 8/11/2020 2:11 PM, Patricio Chilano wrote:
>> Hi all,
>>
>> Please review the following small fix which involves removing the 
>> added HandleMark in BiasedLocking::preserve_marks():
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8251118
>> Webrev: http://cr.openjdk.java.net/~pchilanomate/8251118/v1/webrev/
>>
>> I've inspected the callers of BiasedLocking::preserve_marks() and 
>> they all have an assert that the current thread is the VMThread. 
>> Since the VMThread creates a HandleMark object before executing a VM 
>> operation the extra HandleMark added in 8249192 is not needed.
>> I've run tiers1-3 in mach5 with -XX:+UseBiasedLocking and without the 
>> patch I get several crashes in BiasedLocking::restore_marks(). With 
>> the patch tests completed successfully.
>>
>> Thanks,
>> Patricio
>>