RFR: 8257817: Shenandoah: Don't race with conc-weak-in-progress flag in weak-LRB

[Roman Kennke]

On Mon, 7 Dec 2020 18:31:00 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> After concurrent weak root processing, it should perform handshake first to ensure there are no dirty loads (loads have yet processed by barriers) in Java thread, before it resets conc-weak-root-in-progress flag.
> 
> - [x] hotspot_gc_shenandoah

Looks good to me!
Might want to see in a follow-up if binding conc-roots-flag to should_do_class_unloading() is sane.

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1673