Thread, Re-entrant And Thread Safe

http://en.wikipedia.org/wiki/Reentrant_%28subroutine%29

Re-entrant is the fundamental property to thread safety, by definition, leads to thread safety.

Re-entrant function: (all by myself)

• Must hold no static (or global) non-constant data.
• Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller.
• Must not rely on locks to singleton resources.
• Must not modify its own code.[1] (unless executing in its own unique thread storage)
• Must not call non-reentrant computer programs or routines.

Thread safe function: (cooperation needed, because I share something with others)
Synchronize -- protect critical resource from all concurrent threads