RFR [2/3]: 8139247 Improper locking of MethodData::_extra_data_lock

[Peter Zhelezniakov]

Hi,

This is the second backport request in a series of 3: [1], [2], [3]. This fix corrects a flaw that was made in the fix for [1].
The patch from jdk9 did not apply as is. One small change was needed to introduce err_msg that was absent in jdk9 code base.
Tested with Hotspot JTreg tests.
JBS issue: https://bugs.openjdk.java.net/browse/JDK-8139247
Webrev: http://cr.openjdk.java.net/~avoitylov/peterz/8139247/8139247/

Thanks!
Peter

[1] https://bugs.openjdk.java.net/browse/JDK-8057038
[2] https://bugs.openjdk.java.net/browse/JDK-8139247
[3] https://bugs.openjdk.java.net/browse/JDK-8231501