Duplicate all threads or just the calling thread if fork() called?

• What if the child calls exec just after the fork?
• What if child does not call exec and current threads including the thread calling fork are using mutexes.

• Duplicate all threads (POSIX - no, just the calling thread, but...)
• Solaris: fork (all threads duplicated) and fork1 (Only calling thread
• POSIX provides calls to ensure other threads than calling thread do not own mutex locks (duplicated in child process)