os::current_process_id() - Kernel Design Note

カレントプロセスが実行されているプロセッサのプロセッサIDを取得する

//Linux版(jdk7/hotspot/src/os/linux/vm/os_linux.cpp)
int os::current_process_id() {

  // Under the old linux thread library, linux gives each thread
  // its own process id. Because of this each thread will return
  // a different pid if this method were to return the result
  // of getpid(2). Linux provides no api that returns the pid
  // of the launcher thread for the vm. This implementation
  // returns a unique pid, the pid of the launcher thread
  // that starts the vm 'process'.

  // Under the NPTL, getpid() returns the same pid as the
  // launcher thread rather than a unique pid per thread.
  // Use gettid() if you want the old pre NPTL behaviour.

  // if you are looking for the result of a call to getpid() that
  // returns a unique pid for the calling thread, then look at the
  // OSThread::thread_id() method in osThread_linux.hpp file

  return (int)(_initial_pid ? _initial_pid : getpid());
}