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

[Robbin Ehn]

Thanks Ioi!

/Robbin

On 2018-11-13 18:30, Ioi Lam wrote:
> Looks good! Thanks
> 
> - Ioi
> 
> 
> On 11/13/18 8:54 AM, Robbin Ehn wrote:
>> Sorry wrong url's:
>>
>> Inc:
>> http://cr.openjdk.java.net/~rehn/8213574/2/inc/webrev/
>>
>> Full:
>> http://cr.openjdk.java.net/~rehn/8213574/2/full/webrev/
>>
>> /Robbin
>>
>> On 11/13/18 5:53 PM, Robbin Ehn wrote:
>>> 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
>