RFR (XS) 8237080: fatal error: VM thread could block on lock that may be held by a JavaThread during safepoint: SharedDecoder_lock

[Patricio Chilano]

Hi Coleen,

Looks good to me. Not for this change but seems all monitors that are 
_safepoint_check_never should have allow_vm_block to true since they 
will not be held during a safepoint. Based on the output message in 
check_block_state() that's what we are trying to avoid. Also we wouldn't 
be incrementing _no_safepoint_count in no_safepoint_verifier() 
otherwise, which I think is what we want if the monitor has the 
_safepoint_check_never flag.

Thanks,
Patricio

On 1/28/20 6:36 PM, coleen.phillimore at oracle.com wrote:
> Summary: Set allow_vm_block to true for this lock.  It's 
> _safepoint_check_never so it's sort of implied (you can't safepoint 
> holding the lock and block out the vm thread).
>
> open webrev at http://cr.openjdk.java.net/~coleenp/2020/8237080.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8237080
>
> Ran test case with hard-coded failure, and tier1-6.
>
> Thanks,
> Coleen