int get_refcount() { return refcount_; }
friend void intrusive_ptr_add_ref(ActorImpl* actor)
{
- // std::memory_order_relaxed ought to be enough here instead of std::memory_order_seq_cst
- // But then, we have a threading issue when an actor commits a suicide:
- // it seems that in this case, the worker thread kills the last occurrence of the actor
- // while usually, the maestro does so. FIXME: we should change how actors suicide
- actor->refcount_.fetch_add(1, std::memory_order_seq_cst);
+ // This whole memory consistency semantic drives me nuts.
+ // std::memory_order_relaxed proves to not be enough: There is a threading issue when actors commit suicide.
+ // My guess is that the maestro context wants to propagate changes to the actor's fields after the
+ // actor context frees that memory area or something. But I'm not 100% certain of what's going on.
+ // std::memory_order_seq_cst works but that's rather demanding.
+ // AFAIK, std::memory_order_acq_rel works on all tested platforms, so let's stick to it.
+ // Reducing the requirements to _relaxed would require to fix our suicide procedure, which is a messy piece of code.
+ actor->refcount_.fetch_add(1, std::memory_order_acq_rel);
}
friend void intrusive_ptr_release(ActorImpl* actor)
{
