Lock rec issue #725
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Lock rec issue #725
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luke-gruber
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Having it per-ractor is weird because that means two threads in the same ractor can both acquire the lock (if it's through the re-entering version). I don't think that's how it was envisioned to work. Also, it's currently broken if you raise an exception when the lock is held because `rb_ec_vm_lock_rec(ec)` gives you the state of the ractor's lock_rec, and that is saved on the `tag.lock_rec`. This value doesn't necessarily reflect the state of that thread or fiber's lock_rec (or even if that thread or fiber locked the VM lock), so we can't know if we should release it or how many levels to release. I changed it to work per-fiber like ruby mutexes. Now we can trust that the value saved is correct per fiber, and other threads and fibers trying to acquire the VM lock will be blocked by the fiber that acquired. Also, there was a "bug" (I'm not sure it can happen) where if you acquire the VM lock then call rb_fork, you can deadlock. After a fork we should reset ractor.sync.lock_rec to 0, lock_owner to NULL in case the VM lock was held above the `rb_fork` call site.
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WIP, needs discussion.