Read during Evacuation

[Simone Bordet]

Hi,

while studying a bit Shenandoah, I would like to ask your help about
how reads are handled in case of a concurrent evacuation, the
following case:

* Mutator1 reads the fwd_ptr of an object, points to self.
* Mutator2 wants to write to the same object, but GC is in the evacuation phase.
* Mutator2 evacuates the object, CASes the fwd_ptr, updates the field
it wants to write and let's assume that this is a volatile write.
* Mutator1 resumes and follows the old fwd_ptr, and reads a stale value.

How can Mutator1 know that the object has been evacuated _and_ changed?

Is Mutator1 triggering a barrier that performs the evacuation even
during reads because the GC is in the evacuation phase?

Pointers to code to study?

Thanks!

-- 
Simone Bordet
---
Finally, no matter how good the architecture and design are,
to deliver bug-free software with optimal performance and reliability,
the implementation technique must be flawless.   Victoria Livschitz