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
|
/*
* Copyright (c) 1998-2001 Sendmail, Inc. and its suppliers.
* All rights reserved.
* Copyright (c) 1983, 1995-1997 Eric P. Allman. All rights reserved.
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* By using this file, you agree to the terms and conditions set
* forth in the LICENSE file which can be found at the top level of
* the sendmail distribution.
*
*/
#include <sendmail.h>
SM_RCSID("@(#)$Id: lockfile.c,v 8.19 2001/09/11 04:04:55 gshapiro Exp $")
/*
** LOCKFILE -- lock a file using flock or (shudder) fcntl locking
**
** Parameters:
** fd -- the file descriptor of the file.
** filename -- the file name (for error messages). [unused]
** ext -- the filename extension. [unused]
** type -- type of the lock. Bits can be:
** LOCK_EX -- exclusive lock.
** LOCK_NB -- non-blocking.
** LOCK_UN -- unlock.
**
** Returns:
** true if the lock was acquired.
** false otherwise.
*/
bool
lockfile(fd, filename, ext, type)
int fd;
char *filename;
char *ext;
int type;
{
#if !HASFLOCK
int action;
struct flock lfd;
extern int errno;
memset(&lfd, '\0', sizeof lfd);
if (bitset(LOCK_UN, type))
lfd.l_type = F_UNLCK;
else if (bitset(LOCK_EX, type))
lfd.l_type = F_WRLCK;
else
lfd.l_type = F_RDLCK;
if (bitset(LOCK_NB, type))
action = F_SETLK;
else
action = F_SETLKW;
if (fcntl(fd, action, &lfd) >= 0)
return true;
/*
** On SunOS, if you are testing using -oQ/tmp/mqueue or
** -oA/tmp/aliases or anything like that, and /tmp is mounted
** as type "tmp" (that is, served from swap space), the
** previous fcntl will fail with "Invalid argument" errors.
** Since this is fairly common during testing, we will assume
** that this indicates that the lock is successfully grabbed.
*/
if (errno == EINVAL)
return true;
#else /* !HASFLOCK */
if (flock(fd, type) >= 0)
return true;
#endif /* !HASFLOCK */
return false;
}
|
