1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
|
/** Test program for POSIX advisory record locking. See also #164669
* (http://bugs.kde.org/show_bug.cgi?id=164669).
* See also http://www.opengroup.org/onlinepubs/007908799/xsh/fcntl.html.
*/
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include "tests/sys_mman.h"
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <unistd.h>
/** Lock an entire file exclusively.
*
* @return 1 upon success, 0 upon failure.
*/
static int lock_file(const int fd)
{
struct flock fl;
fl.l_type = F_WRLCK; /* exclusive lock */
fl.l_whence = SEEK_SET;
fl.l_start = 0;
fl.l_len = 0; /* lock entire file */
fl.l_pid = 0;
return fcntl(fd, F_SETLK, &fl) >= 0;
}
static int open_lock_and_map(const char* const process_name,
const char* const filename)
{
int fd;
int flags;
fd = open(filename, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
if (fd < 0)
{
perror("open");
goto err1;
}
flags = fcntl(fd, F_GETFD);
assert(flags >= 0);
if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) < 0)
assert(0);
fprintf(stderr, "%s: about to lock file for writing.\n", process_name);
if (! lock_file(fd))
{
perror("fcntl");
goto err2;
}
fprintf(stderr, "%s: file locking attempt succeeded.\n", process_name);
if (mmap(NULL, 1, PROT_WRITE, MAP_SHARED, fd, 0) == 0)
{
perror("mmap");
goto err2;
}
goto out;
err2:
close(fd);
err1:
out:
return fd;
}
int main(int argc, char *argv[])
{
int fd1;
int fd2;
int exitcode = 1;
char filename[256];
snprintf(filename, sizeof(filename), "/tmp/valgrind-file-locking-test.%ld",
(long) getpid());
unlink(filename);
if ((fd1 = open_lock_and_map("parent", filename)) >= 0)
{
pid_t fork_result;
fork_result = fork();
switch (fork_result)
{
case -1:
perror("fork");
break;
case 0:
/* child */
fd2 = open_lock_and_map("child", filename);
if (fd2 >= 0)
{
close(fd2);
}
exit(0);
break;
default:
/* parent */
{
int child_status;
int wait_result;
wait_result = wait4(fork_result, &child_status, 0, 0);
assert(wait_result >= 0);
}
}
}
close(fd1);
unlink(filename);
fprintf(stderr, "Test finished.\n");
return exitcode;
}
|
