D const enables multi-reader synchronization

[Tomek Sowiński]

This is a continuation of a recent thread "Synchronized const methods" on  
D.learn.

Currently only one thread at a time can execute a synchronized method. But  
think about D's const -- it's deep, so if a method is const, it can't  
possibly mutate its object. So many synchronized const method calls could  
safely look-but-not-touch the same object at the same time.

The chain of questions that stems from the above is:
1. Is letting many readers in on an object really safe? Know any  
multi-threading quirk that would make sh*t hit the fan?
2. If answer to 1. is yes, would there be room in the current  
implementation of synchronized keyword for a readers-writer lock?
3. If answer to 2. is yes, how do we tackle write-starvation? In a  
read-mostly scenario the mutating thread may be held up forever.

More on readers-writer lock:
http://en.wikipedia.org/wiki/Readers-writer_lock


Tomek