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
130
131
132
133
134
|
/*
Copyright (C) 1993, 1994, 1996 Free Software Foundation
This file is part of the GNU Hurd.
The GNU Hurd is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
The GNU Hurd is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with the GNU Hurd; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
/* Written by Michael I. Bushnell. */
#include "locks.h"
#define EWOULDBLOCK EAGAIN /* XXX */
error_t
fshelp_acquire_lock (struct lock_box *box, int *user, pthread_mutex_t *mut,
int flags)
{
if (!(flags & (LOCK_UN | LOCK_EX | LOCK_SH)))
return 0;
if ((flags & LOCK_UN)
&& (flags & (LOCK_SH | LOCK_EX)))
return EINVAL;
if (flags & LOCK_EX)
flags &= ~LOCK_SH;
/* flags now contains exactly one of LOCK_UN, LOCK_SH, or LOCK_EX. */
if (flags & LOCK_UN)
{
if (*user & LOCK_UN)
return 0;
assert (*user == box->type);
assert (*user == LOCK_SH || *user == LOCK_EX);
if (*user == LOCK_SH)
{
if (!--box->shcount)
box->type = LOCK_UN;
}
else if (*user == LOCK_EX)
box->type = LOCK_UN;
if (box->type == LOCK_UN && box->waiting)
{
box->waiting = 0;
pthread_cond_broadcast (&box->wait);
}
*user = LOCK_UN;
}
else
{
/* If we have an exclusive lock, release it. */
if (*user == LOCK_EX)
{
*user = LOCK_UN;
box->type = LOCK_UN;
if (box->waiting)
{
box->waiting = 0;
pthread_cond_broadcast (&box->wait);
}
}
/* If there is an exclusive lock, wait for it to end. */
while (box->type == LOCK_EX)
{
if (flags & LOCK_NB)
return EWOULDBLOCK;
box->waiting = 1;
if (pthread_hurd_cond_wait_np (&box->wait, mut))
return EINTR;
}
/* If we have a shared lock, release it. */
if (*user == LOCK_SH)
{
*user = LOCK_UN;
if (!--box->shcount)
{
box->type = LOCK_UN;
if (box->waiting)
{
box->waiting = 0;
pthread_cond_broadcast (&box->wait);
}
}
}
assert ((flags & LOCK_SH) || (flags & LOCK_EX));
if (flags & LOCK_SH)
{
assert (box->type != LOCK_EX);
*user = LOCK_SH;
box->type = LOCK_SH;
box->shcount++;
}
else if (flags & LOCK_EX)
{
/* Wait for any shared (and exclusive) locks to finish. */
while (box->type != LOCK_UN)
{
if (flags & LOCK_NB)
return EWOULDBLOCK;
else
{
box->waiting = 1;
if (pthread_hurd_cond_wait_np (&box->wait, mut))
return EINTR;
}
}
box->type = LOCK_EX;
*user = LOCK_EX;
}
}
return 0;
}
|
