1 /* $OpenBSD: kqueue-flock.c,v 1.4 2016/09/20 23:05:27 bluhm Exp $ */
2 /*
3 * Written by Philip Guenther <guenther@openbsd.org> 2012 Public Domain
4 */
5
6 #include <sys/types.h>
7 #include <sys/event.h>
8 #include <sys/time.h>
9 #include <sys/wait.h>
10
11 #include <err.h>
12 #include <errno.h>
13 #include <fcntl.h>
14 #include <stdio.h>
15 #include <stdlib.h>
16 #include <string.h>
17 #include <unistd.h>
18
19 #include "main.h"
20
21 #define FILE "lock.test"
22
23 static void
check_lock(int fd,const char * msg)24 check_lock(int fd, const char *msg)
25 {
26 pid_t pid = fork();
27 int status;
28
29 if (pid == -1)
30 err(1, "fork");
31 if (pid == 0) {
32 struct flock fl;
33
34 memset(&fl, 0, sizeof fl);
35 fl.l_type = F_WRLCK;
36 if (fcntl(fd, F_SETLK, &fl) == 0) {
37 printf("lock succeeded %s\n", msg);
38 _exit(1);
39 }
40 if (errno != EAGAIN)
41 err(1, "fcntl(SETLK)");
42 if (fcntl(fd, F_GETLK, &fl))
43 err(1, "fcntl(GETLK)");
44 if (fl.l_type != F_WRLCK) {
45 printf("lock not found %s\n", msg);
46 _exit(1);
47 }
48 close(fd);
49 _exit(0);
50 }
51
52 waitpid(pid, &status, 0);
53 if (! WIFEXITED(status) || WEXITSTATUS(status) != 0)
54 exit(1);
55 }
56
57 int
do_flock(void)58 do_flock(void)
59 {
60 int fd, kq;
61 struct kevent kev;
62 struct flock fl;
63
64 fd = open(FILE, O_CREAT|O_RDWR, 0666);
65 if (fd < 0)
66 err(1, "open");
67 memset(&fl, 0, sizeof fl);
68 fl.l_type = F_WRLCK;
69 if (fcntl(fd, F_SETLK, &fl))
70 err(1, "fcntl(SETLK)");
71
72 check_lock(fd, "before");
73
74 kq = kqueue();
75 EV_SET(&kev, fd, EVFILT_VNODE, EV_ADD, NOTE_LINK, 0, NULL);
76 if (kevent(kq, &kev, 1, NULL, 0, NULL))
77 err(1, "kevent");
78
79 check_lock(fd, "after add");
80
81 EV_SET(&kev, fd, EVFILT_VNODE, EV_DELETE, NOTE_LINK, 0, NULL);
82 if (kevent(kq, &kev, 1, NULL, 0, NULL))
83 err(1, "kevent");
84
85 check_lock(fd, "after delete");
86
87 close(kq);
88
89 check_lock(fd, "after kq close");
90
91 close(fd);
92 unlink(FILE);
93 return (0);
94 }
95