RFR: 8254263: Remove special_runtime_exit_condition() check from ~ThreadInVMForHandshake()

[Daniel D.Daugherty]

On Fri, 9 Oct 2020 14:10:16 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

> Hi all,
> 
> Please review the following patch that removes the call to handle_special_runtime_exit_condition() in
> ~ThreadInVMForHandshake(). This check was added by 8223572 to prevent a JavaThread that was suspended while trying to
> process a handshake to transition back to java without noticing it was suspended. Since 8238761, a JavaThread executing
> HandshakeState::process_by_self() will never become safe. It comes from an unsafe state and remains unsafe, so it
> cannot be suspended during that time. Removing this check also removes one of the reasons
> SafepointMechanism::process_if_requested() is recursive (the other one remains SafepointSynchronize::block()). Tested
> in mach5, tiers 1-7.  Thanks, Patricio

It took me a while to re-read JDK-8223572 and JDK-8238761
and their associated review threads. It's complicated stuff and,
every time I thought I might have an issue, I subsequently
convinced myself all was good.

Thumbs up on this change!

-------------

Marked as reviewed by dcubed (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/577