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Concurrent Systems/notes/5 - Software Transactional Memory.md

@@ -31,4 +31,19 @@ Implementation: every transaction uses a local working space
 - `try_to_commit_T()`: decides whether a transaction (non-aborted) can commit
 
 #### A Logical Clock based STM system
-All the READs perform if no inconsistencies arise, or before any inconsistency
+All the READs perform if no inconsistencies arise, or before any inconsistency
+
+Let T be a transaction; its read prefix is formed by all its successful READ before its possible abortion.
+An execution is **opaque** if all committed transactions and all the read prefixes of all aborted transactions appear if executed one after the other, by following their real-time occurrence order.
+
+We now present an atomic STM system, called *Transactional Locking 2*:
+- CLOCK is an atomic READ/FETCH&ADD register initialized at 0
+- Every MRMW register X is implemented by a pair of register XX s.t.
+	- XX.val contains the value of X
+	- XX.date contains the date (in terms of CLOCK) of the last update
+	- it is associated with a lock object to guarantee MUTEX when updating the shared memory
+- For every transaction T, the invoking process maintains
+	- `lc(XX)`: a local copy of the implementation of reg. X
+	- `read_set(T)`: the set of names of all the registers read by T up to that moment
+	- `write_set(T)`: the set of names of all the registers written by T up to that moment
+	- `birthdate(T)`: the value of CLOCK(+1) at the starting of