Ah, multi-threaded fork, my arch-nemesis. A few points, though I'm not sure any of these are worth mentioning in the book: 1. It should perhaps be made clear that the child's copy of the lock is, in fact, a separate lock. The statement that the lock is held by a parent thread is somewhat inaccurate. That is, unless the lock is in explicitly-shared memory (i.e., the result of mmap(MAP_SHARED)), in which case the lock is indeed the same and is (presumably) meant to be shared between the parent and child. 2. POSIX explicitly says that you can't execute any non-async-signal-safe functions between fork() and exec(), which pretty much eliminates any function that acquires a lock. 3. posix_spawn() is a safer alternative to the fork()/exec() pair (though not to fork() by itself), at least with sensible implementations that don't devolve to fork() and exec(). --Elad
