??????ó?????????????????kill???С?????????“kill”??????????????SIGKILL?????ú????????????????????????sys_kill????????????????????????????

????????????????????id??kill()????????????????飩????????????????????????pid??????????????

?????? pid>0?????????????????????????pid?????

?????? pid=0?????????????????????е??????????

?????? pid=-1????????????κ?????????init?????PID=1???????????????????????????????

?????? pid<-1??????????????????飬??id??????е?pid????????

??????????????????????????

????????sys_kill??????????????????????????????????????????????????????????????????pid??????????????????С?tkill??????????sys_tkill??kernel/signal.c???????????￡?

/*
 *  Send a signal to only one task?? even if it's a CLONE_THREAD task.
 */
asmlinkage long
sys_tkill(int pid?? int sig)
{
 struct siginfo info;
 int error;
 struct task_struct *p;

 /* This is only valid for single tasks */
 if (pid <= 0)//?????pid???м??
  return -EINVAL;

 info.si_signo = sig; //???????????????siginfo??
 info.si_errno = 0;
 info.si_code = SI_TKILL;
 info.si_pid = current->tgid;
 info.si_uid = current->uid;

 read_lock(&tasklist_lock);
 p = find_task_by_pid(pid);//?????pid?????????task_struct??
 error = -ESRCH;
 if (p) {
  error = check_kill_permission(sig?? &info?? p);//?????
  /*
   * The null signal is a permissions and process existence
   * probe.  No signal is actually delivered.
   */
  if (!error && sig && p->sighand) {
   spin_lock_irq(&p->sighand->siglock);
   handle_stop_signal(sig?? p);
   //???Щ?????????????????統(tǒng)???SIGSTOP???????????????е?SIGCONT??????
   error = specific_send_sig_info(sig?? &info?? p);//??????????????
   spin_unlock_irq(&p->sighand->siglock);
  }
 }
 read_unlock(&tasklist_lock);
 return error;
}