[cpp-threads] A draft memory model paper

[Peter Dimov]

Herb Sutter wrote:

>   http://www.gotw.ca/memmodel/Prism%20-%20draft%200.8.pdf

There are some interesting parts that might need clarification.

R3 states that "Interlocked reads and writes by the same observer cannot be 
reordered relative to one another and shall be performed in program order." 
However, example 3.2.2 appears to contradict that by stating that an 
interlocked write followed by an interlocked read can be reordered.

Examples claim that a preceding non-interlocked operation can be moved 
inside a critical section (which corresponds to acquire semantics for lock). 
This appears to contradict the definition of lock as an interlocked 
read-modify-write and example 3.2.5. In 3.2.5, if v1 = 1 can be moved after 
lock(l1), then the example does contain a race.

The absence of atomic non-interlocked operations is somewhat disturbing... 
efficient reference counting needs an atomic increment (fetchadd<raw>(1)).