[8u] RFR 8254673: call for JvmtiExport::post_vm_start() was removed by the fix for JDK-8249158

[Andrew Brygin]

Hello,

 please review a fix for 8254673.

Bug: https://bugs.openjdk.java.net/browse/JDK-8254673
Webrev: http://cr.openjdk.java.net/~bae/8u/8254673/webrev.00/

 The fix for JDK-8249158 [1] removes the call for
JvmtiExport::post_vm_start() from Threads::create_vm():

https://hg.openjdk.java.net/jdk8u/jdk8u-dev/hotspot/rev/85e682d8ab91#l11.24

 This fix is supposed to be a backout of the fix for JDK-8233197 [2], so
this removal seems to be done by a mistake, because the call for
JvmtiExport::post_vm_start() was present there prior to the fix for
JDK-8233197:
https://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/rev/26d1803768c7#l11.21

 This change causes failures in the vmTestbase suite [3], which is not
yet included into jdk8u though. Probably some jvmti usecases could be
affected also.

Thanks,
Andrew.

[1] https://bugs.openjdk.java.net/browse/JDK-8249158
[2] https://bugs.openjdk.java.net/browse/JDK-8233197
[3]
http://mail.openjdk.java.net/pipermail/jdk8u-dev/2020-January/010900.html