1 /*
2  * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 #include <sys/types.h>
17 #include <sys/stat.h>
18 #include <fcntl.h>
19 #include <errno.h>
20 #include <unistd.h>
21 
22 int main(void)
23 {
24 	char buf[64];
25 	int fd;
26 
27 	fd = open("/proc/self/wchan", O_RDONLY);
28 	if (fd == -1) {
29 		if (errno == ENOENT)
30 			return 4;
31 		return 1;
32 	}
33 
34 	buf[0] = '\0';
35 	if (read(fd, buf, sizeof(buf)) != 1)
36 		return 1;
37 	if (buf[0] != '0')
38 		return 1;
39 	return 0;
40 }
41