RFR(s): 8213574: Deadlock in string table expansion when dumping lots of CDS classes

[Robbin Ehn]

Hi, here is small incremental update:

http://rehn-ws.se.oracle.com/cr_mirror/8213574/2/inc/webrev/index.html

Full:
http://rehn-ws.se.oracle.com/cr_mirror/8213574/2/full/webrev/

Passes t1-3 and the reprod in 8213587.

Thanks, Robbin

On 11/12/18 2:59 PM, Robbin Ehn wrote:
> Hi all, please review.
> 
> The re-sizing operation is run by the ServiceThread (JavaThread). To be 
> safepoint polite it pauses the operation and do safepoint checks. Operations on
> the hashtable that visit multiple bucket are mutual exclusive. This means you
> can't iterate over the table during a safepoint if there is paused resize.
> 
> The hashtable uses a Mutex, which means if there were other threads using it
> during the safepoint the VM thread sneaking would break it. Since there are no 
> such users it is safe to access it without locks in side the safepoint. That is
> how rehash works today.
> 
> Until we sorted this out better in 8213742,  I'm adding a safepoint scanning
> operation that can handle a paused resize and which skips the lock.
> 
> CR: https://bugs.openjdk.java.net/browse/JDK-8213574
> Webrev: http://cr.openjdk.java.net/~rehn/8213574/webrev/
> 
> Passes t1-3 and 8213587 new test which triggered the issue.
> 
> Thanks, Robbin