Function tty_wait_background

components/lwp/terminal/freebsd/tty.c:414–496

}

int tty_wait_background(struct lwp_tty *tp, struct rt_thread *td, int sig)
{
    struct rt_lwp *p;
    struct rt_processgroup *pg;
    int error;

    MPASS(sig == SIGTTIN || sig == SIGTTOU);
    tty_assert_locked(tp);

    p = td->lwp;
    for (;;)
    {
        pg = p->pgrp;
        PGRP_LOCK(pg);
        LWP_LOCK(p);

        /*
         * pg may no longer be our process group.
         * Re-check after locking.
         */
        if (p->pgrp != pg)
        {
            LWP_UNLOCK(p);
            PGRP_UNLOCK(pg);
            continue;
        }

        /*
         * The process should only sleep, when:
         * - This terminal is the controlling terminal
         * - Its process group is not the foreground process
         *   group
         * - The parent process isn't waiting for the child to
         *   exit
         * - the signal to send to the process isn't masked
         */
        if (!tty_is_ctty(tp, p) || pg == tp->t_pgrp)
        {
            /* Allow the action to happen. */
            LWP_UNLOCK(p);
            PGRP_UNLOCK(pg);
            return 0;
        }

        /* Note: process itself don't have a sigmask in smart */
        if (lwp_sigisign(p, sig) ||
            lwp_sigismember(&td->signal.sigset_mask, sig))
        {
            /* Only allow them in write()/ioctl(). */
            LWP_UNLOCK(p);
            PGRP_UNLOCK(pg);
            return (sig == SIGTTOU ? 0 : -EIO);
        }

#ifdef USING_VFORK_FLAG
        if ((p->p_flag & P_PPWAIT) != 0 || pg->is_orphaned)
#else
        if (pg->is_orphaned)