mtctxres.c revision 156956
1#include <sys/cdefs.h> 2__FBSDID("$FreeBSD: head/lib/libc/resolv/mtctxres.c 156956 2006-03-21 15:37:16Z ume $"); 3 4#include <port_before.h> 5#ifdef DO_PTHREADS 6#include <pthread.h> 7#ifdef _LIBC 8#include <pthread_np.h> 9#endif 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 <port_after.h> 17 18#ifdef DO_PTHREADS 19static pthread_key_t key; 20static int mt_key_initialized = 0; 21 22static int __res_init_ctx(void); 23static void __res_destroy_ctx(void *); 24 25#if defined(sun) && !defined(__GNUC__) 26#pragma init (_mtctxres_init) 27#endif 28#endif 29 30static mtctxres_t sharedctx; 31 32#ifdef DO_PTHREADS 33/* 34 * Initialize the TSD key. By doing this at library load time, we're 35 * implicitly running without interference from other threads, so there's 36 * no need for locking. 37 */ 38static void 39_mtctxres_init(void) { 40 int pthread_keycreate_ret; 41 42 pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx); 43 if (pthread_keycreate_ret == 0) 44 mt_key_initialized = 1; 45} 46#endif 47 48#ifndef _LIBC 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 */ 54int 55__res_enable_mt(void) { 56 return (-1); 57} 58 59int 60__res_disable_mt(void) { 61 return (0); 62} 63#endif 64 65#ifdef DO_PTHREADS 66static int 67__res_init_ctx(void) { 68 69 mtctxres_t *mt; 70 int ret; 71 72 73 if (pthread_getspecific(key) != 0) { 74 /* Already exists */ 75 return (0); 76 } 77 78 if ((mt = malloc(sizeof (mtctxres_t))) == 0) { 79 errno = ENOMEM; 80 return (-1); 81 } 82 83 memset(mt, 0, sizeof (mtctxres_t)); 84 85 if ((ret = pthread_setspecific(key, mt)) != 0) { 86 free(mt); 87 errno = ret; 88 return (-1); 89 } 90 91 return (0); 92} 93 94static void 95__res_destroy_ctx(void *value) { 96 97 mtctxres_t *mt = (mtctxres_t *)value; 98 99 if (mt != 0) 100 free(mt); 101} 102#endif 103 104mtctxres_t * 105___mtctxres(void) { 106#ifdef DO_PTHREADS 107 mtctxres_t *mt; 108 109#ifdef _LIBC 110 if (pthread_main_np() != 0) 111 return (&sharedctx); 112#endif 113 114 /* 115 * This if clause should only be executed if we are linking 116 * statically. When linked dynamically _mtctxres_init() should 117 * be called at binding time due the #pragma above. 118 */ 119 if (!mt_key_initialized) { 120 static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER; 121 pthread_mutex_lock(&keylock); 122 _mtctxres_init(); 123 pthread_mutex_unlock(&keylock); 124 } 125 126 /* 127 * If we have already been called in this thread return the existing 128 * context. Otherwise recreat a new context and return it. If 129 * that fails return a global context. 130 */ 131 if (mt_key_initialized) { 132 if (((mt = pthread_getspecific(key)) != 0) || 133 (__res_init_ctx() == 0 && 134 (mt = pthread_getspecific(key)) != 0)) { 135 return (mt); 136 } 137 } 138#endif 139 return (&sharedctx); 140} 141