RFR: 8244551: Shenandoah: Fix racy update of update_watermark

[Aleksey Shipilev]

On 5/7/20 1:06 PM, Roman Kennke wrote:
> http://cr.openjdk.java.net/~rkennke/JDK-8244551/webrev.01/

Nice.

*) What's the point of this cast?

 133   *const_cast<HeapWord**>(&_update_watermark) =  w;

*) Nit: message can be shorter "Should be at Shenandoah safepoint"

 131   assert(SafepointSynchronize::is_at_safepoint(),
 132          "only call set_update_watermark_at_safepoint at safepoint");


-- 
Thanks,
-Aleksey