Function pipe_paircreate

freebsd/kern/sys_pipe.c:339–395

}

static int
pipe_paircreate(struct thread *td, struct pipepair **p_pp)
{
	struct pipepair *pp;
	struct pipe *rpipe, *wpipe;
	int error;

	*p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
#ifdef MAC
	/*
	 * The MAC label is shared between the connected endpoints.  As a
	 * result mac_pipe_init() and mac_pipe_create() are called once
	 * for the pair, and not on the endpoints.
	 */
	mac_pipe_init(pp);
	mac_pipe_create(td->td_ucred, pp);
#endif
	rpipe = &pp->pp_rpipe;
	wpipe = &pp->pp_wpipe;

	knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
	knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));

	/*
	 * Only the forward direction pipe is backed by big buffer by
	 * default.
	 */
	error = pipe_create(rpipe, true);
	if (error != 0)
		goto fail;
	error = pipe_create(wpipe, false);
	if (error != 0) {
		/*
		 * This cleanup leaves the pipe inode number for rpipe
		 * still allocated, but never used.  We do not free
		 * inode numbers for opened pipes, which is required
		 * for correctness because numbers must be unique.
		 * But also it avoids any memory use by the unr
		 * allocator, so stashing away the transient inode
		 * number is reasonable.
		 */
		pipe_free_kmem(rpipe);
		goto fail;
	}

	rpipe->pipe_state |= PIPE_DIRECTOK;
	wpipe->pipe_state |= PIPE_DIRECTOK;
	return (0);

fail:
	knlist_destroy(&rpipe->pipe_sel.si_note);
	knlist_destroy(&wpipe->pipe_sel.si_note);
#ifdef MAC
	mac_pipe_destroy(pp);
#endif
	return (error);
}