1/*
2 * Copyright (c) 2021 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// Test that /proc/*/task never contains "0".
17#include <sys/types.h>
18#include <dirent.h>
19#include <signal.h>
20#include <stdio.h>
21#include <stdlib.h>
22#include <string.h>
23#include <unistd.h>
24#include <pthread.h>
25
26static pid_t pid = -1;
27
28static void atexit_hook(void)
29{
30	if (pid > 0) {
31		kill(pid, SIGKILL);
32	}
33}
34
35static void *f(void *_)
36{
37	return NULL;
38}
39
40static void sigalrm(int _)
41{
42	exit(0);
43}
44
45int main(void)
46{
47	pid = fork();
48	if (pid == 0) {
49		/* child */
50		while (1) {
51			pthread_t pth;
52			pthread_create(&pth, NULL, f, NULL);
53			pthread_join(pth, NULL);
54		}
55	} else if (pid > 0) {
56		/* parent */
57		atexit(atexit_hook);
58
59		char buf[64];
60		snprintf(buf, sizeof(buf), "/proc/%u/task", pid);
61
62		signal(SIGALRM, sigalrm);
63		alarm(1);
64
65		while (1) {
66			DIR *d = opendir(buf);
67			struct dirent *de;
68			while ((de = readdir(d))) {
69				if (strcmp(de->d_name, "0") == 0) {
70					exit(1);
71				}
72			}
73			closedir(d);
74		}
75
76		return 0;
77	} else {
78		perror("fork");
79		return 1;
80	}
81}
82