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
|
/********************************************************
* An example source module to accompany...
*
* "Using POSIX Threads: Programming with Pthreads"
* by Brad nichols, Dick Buttlar, Jackie Farrell
* O'Reilly & Associates, Inc.
*
********************************************************
* rdwr.c --
*
* Library of functions implementing reader/writer locks
*/
#include <pthread.h>
#include "rdwr.h"
int
pthread_rdwr_init_np (pthread_rdwr_t * rdwrp)
{
rdwrp->readers_reading = 0;
rdwrp->writer_writing = 0;
pthread_mutex_init (&(rdwrp->mutex), NULL);
pthread_cond_init (&(rdwrp->lock_free), NULL);
return 0;
}
int
pthread_rdwr_rlock_np (pthread_rdwr_t * rdwrp)
{
pthread_mutex_lock (&(rdwrp->mutex));
while (rdwrp->writer_writing)
{
pthread_cond_wait (&(rdwrp->lock_free), &(rdwrp->mutex));
}
rdwrp->readers_reading++;
pthread_mutex_unlock (&(rdwrp->mutex));
return 0;
}
int
pthread_rdwr_runlock_np (pthread_rdwr_t * rdwrp)
{
pthread_mutex_lock (&(rdwrp->mutex));
if (rdwrp->readers_reading == 0)
{
pthread_mutex_unlock (&(rdwrp->mutex));
return -1;
}
else
{
rdwrp->readers_reading--;
if (rdwrp->readers_reading == 0)
{
pthread_cond_signal (&(rdwrp->lock_free));
}
pthread_mutex_unlock (&(rdwrp->mutex));
return 0;
}
}
int
pthread_rdwr_wlock_np (pthread_rdwr_t * rdwrp)
{
pthread_mutex_lock (&(rdwrp->mutex));
while (rdwrp->writer_writing || rdwrp->readers_reading)
{
pthread_cond_wait (&(rdwrp->lock_free), &(rdwrp->mutex));
}
rdwrp->writer_writing++;
pthread_mutex_unlock (&(rdwrp->mutex));
return 0;
}
int
pthread_rdwr_wunlock_np (pthread_rdwr_t * rdwrp)
{
pthread_mutex_lock (&(rdwrp->mutex));
if (rdwrp->writer_writing == 0)
{
pthread_mutex_unlock (&(rdwrp->mutex));
return -1;
}
else
{
rdwrp->writer_writing = 0;
pthread_cond_broadcast (&(rdwrp->lock_free));
pthread_mutex_unlock (&(rdwrp->mutex));
return 0;
}
}
|
