mtctxres.c revision a210cae724313604f8cbd49cc6deab1be5239083 
1/*	$NetBSD: mtctxres.c,v 1.4 2007/03/30 20:40:52 ghen Exp $	*/
2
3#include <port_before.h>
4#ifdef DO_PTHREADS
5#include <pthread.h>
6#endif
7#include <errno.h>
8#include <netdb.h>
9#include <stdlib.h>
10#include <string.h>
11#include <resolv_mt.h>
12#include <port_after.h>
13
14#ifdef DO_PTHREADS
15static pthread_key_t	key;
16static int		mt_key_initialized = 0;
17
18static int		__res_init_ctx(void);
19static void		__res_destroy_ctx(void *);
20
21#if defined(sun) && !defined(__GNUC__)
22#pragma init	(_mtctxres_init)
23#endif
24#endif
25
26static mtctxres_t	sharedctx;
27
28#ifdef DO_PTHREADS
29/*
30 * Initialize the TSD key. By doing this at library load time, we're
31 * implicitly running without interference from other threads, so there's
32 * no need for locking.
33 */
34static void
35_mtctxres_init(void) {
36	int pthread_keycreate_ret;
37
38	pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx);
39	if (pthread_keycreate_ret == 0)
40		mt_key_initialized = 1;
41}
42#endif
43
44/*
45 * To support binaries that used the private MT-safe interface in
46 * Solaris 8, we still need to provide the __res_enable_mt()
47 * and __res_disable_mt() entry points. They're do-nothing routines.
48 */
49int
50__res_enable_mt(void) {
51	return (-1);
52}
53
54int
55__res_disable_mt(void) {
56	return (0);
57}
58
59#ifdef DO_PTHREADS
60static int
61__res_init_ctx(void) {
62
63	mtctxres_t	*mt;
64	int		ret;
65
66
67	if (pthread_getspecific(key) != 0) {
68		/* Already exists */
69		return (0);
70	}
71
72	if ((mt = malloc(sizeof (mtctxres_t))) == 0) {
73		errno = ENOMEM;
74		return (-1);
75	}
76
77	memset(mt, 0, sizeof (mtctxres_t));
78
79	if ((ret = pthread_setspecific(key, mt)) != 0) {
80		free(mt);
81		errno = ret;
82		return (-1);
83	}
84
85	return (0);
86}
87
88static void
89__res_destroy_ctx(void *value) {
90
91	mtctxres_t	*mt = (mtctxres_t *)value;
92
93	if (mt != 0)
94		free(mt);
95}
96#endif
97
98mtctxres_t *
99___mtctxres(void) {
100#ifdef DO_PTHREADS
101	mtctxres_t	*mt;
102
103	/*
104	 * This if clause should only be executed if we are linking
105	 * statically.  When linked dynamically _mtctxres_init() should
106	 * be called at binding time due the #pragma above.
107	 */
108	if (!mt_key_initialized) {
109		static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER;
110                if (pthread_mutex_lock(&keylock) == 0) {
111			_mtctxres_init();
112			(void) pthread_mutex_unlock(&keylock);
113		}
114	}
115
116	/*
117	 * If we have already been called in this thread return the existing
118	 * context.  Otherwise recreat a new context and return it.  If
119	 * that fails return a global context.
120	 */
121	if (mt_key_initialized) {
122		if (((mt = pthread_getspecific(key)) != 0) ||
123		    (__res_init_ctx() == 0 &&
124		     (mt = pthread_getspecific(key)) != 0)) {
125			return (mt);
126		}
127	}
128#endif
129	return (&sharedctx);
130}
131