1 /* vi: set sw=4 ts=4: */
3 * Signal pipe infrastructure. A reliable way of delivering signals.
5 * Russ Dill <Russ.Dill@asu.edu> December 2003
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 /* Global variable: we access it from signal handler */
24 static struct fd_pair signal_pipe;
26 static void signal_handler(int sig)
29 unsigned char ch = sig; /* use char, avoid dealing with partial writes */
30 if (write(signal_pipe.wr, &ch, 1) != 1)
31 bb_perror_msg("can't send signal");
35 /* Call this before doing anything else. Sets up the socket pair
36 * and installs the signal handler */
37 void FAST_FUNC udhcp_sp_setup(void)
39 /* was socketpair, but it needs AF_UNIX in kernel */
40 xpiped_pair(signal_pipe);
41 close_on_exec_on(signal_pipe.rd);
42 close_on_exec_on(signal_pipe.wr);
43 ndelay_on(signal_pipe.wr);
51 /* Quick little function to setup the pfds.
52 * Limited in that you can only pass one extra fd.
54 void FAST_FUNC udhcp_sp_fd_set(struct pollfd pfds[2], int extra_fd)
56 pfds[0].fd = signal_pipe.rd;
57 pfds[0].events = POLLIN;
60 close_on_exec_on(extra_fd);
61 pfds[1].fd = extra_fd;
62 pfds[1].events = POLLIN;
66 /* Read a signal from the signal pipe. Returns 0 if there is
67 * no signal, -1 on error (and sets errno appropriately), and
68 * your signal on success */
69 int FAST_FUNC udhcp_sp_read(struct pollfd pfds[2])
76 if (safe_read(signal_pipe.rd, &sig, 1) != 1)