xref: /titanic_51/usr/src/lib/libresolv2/common/resolv/mtctxres.c (revision 7014882c6a3672fd0e5d60200af8643ae53c5928)
1 /*
2  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
3  * Use is subject to license terms.
4  */
5 
6 
7 #include <port_before.h>
8 #ifdef DO_PTHREADS
9 #include <pthread.h>
10 #endif
11 #include <errno.h>
12 #include <netdb.h>
13 #include <stdlib.h>
14 #include <string.h>
15 #include <resolv_mt.h>
16 #include <irs.h>
17 #include <port_after.h>
18 
19 #ifdef DO_PTHREADS
20 static pthread_key_t	key;
21 static int		mt_key_initialized = 0;
22 
23 static int		__res_init_ctx(void);
24 static void		__res_destroy_ctx(void *);
25 
26 #if defined(sun) && !defined(__GNUC__)
27 #pragma init	(_mtctxres_init)
28 #endif
29 #endif
30 
31 static mtctxres_t	sharedctx;
32 
33 #ifdef DO_PTHREADS
34 /*
35  * Initialize the TSD key. By doing this at library load time, we're
36  * implicitly running without interference from other threads, so there's
37  * no need for locking.
38  */
39 static void
40 _mtctxres_init(void) {
41 	int pthread_keycreate_ret;
42 
43 	pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx);
44 	if (pthread_keycreate_ret == 0)
45 		mt_key_initialized = 1;
46 }
47 #endif
48 
49 /*
50  * To support binaries that used the private MT-safe interface in
51  * Solaris 8, we still need to provide the __res_enable_mt()
52  * and __res_disable_mt() entry points. They're do-nothing routines.
53  */
54 int
55 __res_enable_mt(void) {
56 	return (-1);
57 }
58 
59 int
60 __res_disable_mt(void) {
61 	return (0);
62 }
63 
64 #ifdef DO_PTHREADS
65 static int
66 __res_init_ctx(void) {
67 
68 	mtctxres_t	*mt;
69 	int		ret;
70 
71 
72 	if (pthread_getspecific(key) != 0) {
73 		/* Already exists */
74 		return (0);
75 	}
76 
77 	if ((mt = malloc(sizeof (mtctxres_t))) == 0) {
78 		errno = ENOMEM;
79 		return (-1);
80 	}
81 
82 	memset(mt, 0, sizeof (mtctxres_t));
83 
84 	if ((ret = pthread_setspecific(key, mt)) != 0) {
85 		free(mt);
86 		errno = ret;
87 		return (-1);
88 	}
89 
90 	return (0);
91 }
92 
93 static void
94 __res_destroy_ctx(void *value) {
95 
96 	mtctxres_t	*mt = (mtctxres_t *)value;
97 
98 	if (mt != 0)
99 		free(mt);
100 }
101 #endif
102 
103 mtctxres_t *
104 ___mtctxres(void) {
105 #ifdef DO_PTHREADS
106 	mtctxres_t	*mt;
107 
108 	/*
109 	 * This if clause should only be executed if we are linking
110 	 * statically.  When linked dynamically _mtctxres_init() should
111 	 * be called at binding time due the #pragma above.
112 	 */
113 	if (!mt_key_initialized) {
114 		static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER;
115                 if (pthread_mutex_lock(&keylock) == 0) {
116 			_mtctxres_init();
117 			(void) pthread_mutex_unlock(&keylock);
118 		}
119 	}
120 
121 	/*
122 	 * If we have already been called in this thread return the existing
123 	 * context.  Otherwise recreat a new context and return it.  If
124 	 * that fails return a global context.
125 	 */
126 	if (mt_key_initialized) {
127 		if (((mt = pthread_getspecific(key)) != 0) ||
128 		    (__res_init_ctx() == 0 &&
129 		     (mt = pthread_getspecific(key)) != 0)) {
130 			return (mt);
131 		}
132 	}
133 #endif
134 	return (&sharedctx);
135 }
136