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 
26 static pid_t pid = -1;
27 
28 static void atexit_hook(void)
29 {
30 	if (pid > 0) {
31 		kill(pid, SIGKILL);
32 	}
33 }
34 
35 static void *f(void *_)
36 {
37 	return NULL;
38 }
39 
40 static void sigalrm(int _)
41 {
42 	exit(0);
43 }
44 
45 int 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