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
|
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <pthread.h>
pthread_t th[5] = {0};
void
flock_init (struct flock *f, short int type, off_t start, off_t len)
{
f->l_type = type;
f->l_start = start;
f->l_len = len;
}
int
flock_range_in_steps (int fd, int is_set, short l_type,
int start, int end, int step)
{
int ret = 0;
int i = 0;
struct flock f = {0,};
for (i = start; i+step < end; i += step) {
flock_init (&f, l_type, i, step);
ret = fcntl (fd, (is_set)? F_SETLKW:F_GETLK, &f);
if (ret) {
perror ("fcntl");
goto out;
}
}
out:
return ret;
}
void *
random_locker (void *arg)
{
int fd = *(int *)arg;
int i = 0;
int is_set = 0;
/* use thread id to choose GETLK or SETLK operation*/
is_set = pthread_self () % 2;
(void)flock_range_in_steps (fd, is_set, F_WRLCK, 0, 400, 1);
return NULL;
}
int main (int argc, char **argv)
{
int fd = -1;
int ret = 1;
int i = 0;
char *fname = NULL;
if (argc < 2)
goto out;
fname = argv[1];
fd = open (fname, O_RDWR);
if (fd == -1) {
perror ("open");
goto out;
}
ret = flock_range_in_steps (fd, 1, F_WRLCK, 0, 2000, 2);
for (i = 0; i < 5; i++) {
pthread_create (&th[i], NULL, random_locker, (void *) &fd);
}
ret = flock_range_in_steps (fd, 1, F_WRLCK, 0, 2000, 2);
for (i = 0; i < 5; i++) {
pthread_join (th[i], NULL);
}
out:
if (fd != -1)
close (fd);
return ret;
}
|
