src/mesa/glapi/glapi.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  7.1
   4  *
   5  * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 /*
  27  * This file manages the OpenGL API dispatch layer.
  28  * The dispatch table (struct _glapi_table) is basically just a list
  29  * of function pointers.
  30  * There are functions to set/get the current dispatch table for the
  31  * current thread and to manage registration/dispatch of dynamically
  32  * added extension functions.
  33  *
  34  * It's intended that this file and the other glapi*.[ch] files are
  35  * flexible enough to be reused in several places:  XFree86, DRI-
  36  * based libGL.so, and perhaps the SGI SI.
  37  *
  38  * NOTE: There are no dependencies on Mesa in this code.
  39  *
  40  * Versions (API changes):
  41  *   2000/02/23  - original version for Mesa 3.3 and XFree86 4.0
  42  *   2001/01/16  - added dispatch override feature for Mesa 3.5
  43  *   2002/06/28  - added _glapi_set_warning_func(), Mesa 4.1.
  44  *   2002/10/01  - _glapi_get_proc_address() will now generate new entrypoints
  45  *                 itself (using offset ~0).  _glapi_add_entrypoint() can be
  46  *                 called afterward and it'll fill in the correct dispatch
  47  *                 offset.  This allows DRI libGL to avoid probing for DRI
  48  *                 drivers!  No changes to the public glapi interface.
  49  */
  50
  51
  52
  53 #ifdef HAVE_DIX_CONFIG_H
  54 #include <dix-config.h>
  55 #include "glapi/mesa.h"
  56 #else
  57 #include "main/glheader.h"
  58 #include "main/compiler.h"
  59 #endif
  60
  61 #include "glapi/glapi.h"
  62 #include "glapi/glapi_priv.h"
  63
  64 extern _glapi_proc __glapi_noop_table[];
  65
  66
  67 /**
  68  * \name Current dispatch and current context control variables
  69  *
  70  * Depending on whether or not multithreading is support, and the type of
  71  * support available, several variables are used to store the current context
  72  * pointer and the current dispatch table pointer.  In the non-threaded case,
  73  * the variables \c _glapi_Dispatch and \c _glapi_Context are used for this
  74  * purpose.
  75  *
  76  * In the "normal" threaded case, the variables \c _glapi_Dispatch and
  77  * \c _glapi_Context will be \c NULL if an application is detected as being
  78  * multithreaded.  Single-threaded applications will use \c _glapi_Dispatch
  79  * and \c _glapi_Context just like the case without any threading support.
  80  * When \c _glapi_Dispatch and \c _glapi_Context are \c NULL, the thread state
  81  * data \c _gl_DispatchTSD and \c ContextTSD are used.  Drivers and the
  82  * static dispatch functions access these variables via \c _glapi_get_dispatch
  83  * and \c _glapi_get_context.
  84  *
  85  * There is a race condition in setting \c _glapi_Dispatch to \c NULL.  It is
  86  * possible for the original thread to be setting it at the same instant a new
  87  * thread, perhaps running on a different processor, is clearing it.  Because
  88  * of that, \c ThreadSafe, which can only ever be changed to \c GL_TRUE, is
  89  * used to determine whether or not the application is multithreaded.
  90  *
  91  * In the TLS case, the variables \c _glapi_Dispatch and \c _glapi_Context are
  92  * hardcoded to \c NULL.  Instead the TLS variables \c _glapi_tls_Dispatch and
  93  * \c _glapi_tls_Context are used.  Having \c _glapi_Dispatch and
  94  * \c _glapi_Context be hardcoded to \c NULL maintains binary compatability
  95  * between TLS enabled loaders and non-TLS DRI drivers.
  96  */
  97 /*@{*/
  98 #if defined(GLX_USE_TLS)
  99
 100 PUBLIC __thread struct _glapi_table * _glapi_tls_Dispatch
 101     __attribute__((tls_model("initial-exec")))
 102     = (struct _glapi_table *) __glapi_noop_table;
 103
 104 PUBLIC __thread void * _glapi_tls_Context
 105     __attribute__((tls_model("initial-exec")));
 106
 107 PUBLIC const struct _glapi_table *_glapi_Dispatch = NULL;
 108
 109 PUBLIC const void *_glapi_Context = NULL;
 110
 111 #else
 112
 113 #if defined(THREADS)
 114
 115 static GLboolean ThreadSafe = GL_FALSE;  /**< In thread-safe mode? */
 116
 117 _glthread_TSD _gl_DispatchTSD;           /**< Per-thread dispatch pointer */
 118
 119 static _glthread_TSD ContextTSD;         /**< Per-thread context pointer */
 120
 121 #endif /* defined(THREADS) */
 122
 123 PUBLIC struct _glapi_table *_glapi_Dispatch = (struct _glapi_table *) __glapi_noop_table;
 124
 125 PUBLIC void *_glapi_Context = NULL;
 126
 127 #endif /* defined(GLX_USE_TLS) */
 128 /*@}*/
 129
 130
 131
 132 #if defined(THREADS) && !defined(GLX_USE_TLS)
 133
 134 void
 135 _glapi_init_multithread(void)
 136 {
 137    _glthread_InitTSD(&_gl_DispatchTSD);
 138    _glthread_InitTSD(&ContextTSD);
 139 }
 140
 141 void
 142 _glapi_destroy_multithread(void)
 143 {
 144 #ifdef WIN32_THREADS
 145    _glthread_DestroyTSD(&_gl_DispatchTSD);
 146    _glthread_DestroyTSD(&ContextTSD);
 147 #endif
 148 }
 149
 150 /**
 151  * Mutex for multithread check.
 152  */
 153 #ifdef WIN32_THREADS
 154 /* _glthread_DECLARE_STATIC_MUTEX is broken on windows.  There will be race! */
 155 #define CHECK_MULTITHREAD_LOCK()
 156 #define CHECK_MULTITHREAD_UNLOCK()
 157 #else
 158 _glthread_DECLARE_STATIC_MUTEX(ThreadCheckMutex);
 159 #define CHECK_MULTITHREAD_LOCK() _glthread_LOCK_MUTEX(ThreadCheckMutex)
 160 #define CHECK_MULTITHREAD_UNLOCK() _glthread_UNLOCK_MUTEX(ThreadCheckMutex)
 161 #endif
 162
 163 /**
 164  * We should call this periodically from a function such as glXMakeCurrent
 165  * in order to test if multiple threads are being used.
 166  */
 167 PUBLIC void
 168 _glapi_check_multithread(void)
 169 {
 170    static unsigned long knownID;
 171    static GLboolean firstCall = GL_TRUE;
 172
 173    if (ThreadSafe)
 174       return;
 175
 176    CHECK_MULTITHREAD_LOCK();
 177    if (firstCall) {
 178       _glapi_init_multithread();
 179
 180       knownID = _glthread_GetID();
 181       firstCall = GL_FALSE;
 182    }
 183    else if (knownID != _glthread_GetID()) {
 184       ThreadSafe = GL_TRUE;
 185       _glapi_set_dispatch(NULL);
 186       _glapi_set_context(NULL);
 187    }
 188    CHECK_MULTITHREAD_UNLOCK();
 189 }
 190
 191 #else
 192
 193 void
 194 _glapi_init_multithread(void) { }
 195
 196 void
 197 _glapi_destroy_multithread(void) { }
 198
 199 PUBLIC void
 200 _glapi_check_multithread(void) { }
 201
 202 #endif
 203
 204
 205
 206 /**
 207  * Set the current context pointer for this thread.
 208  * The context pointer is an opaque type which should be cast to
 209  * void from the real context pointer type.
 210  */
 211 PUBLIC void
 212 _glapi_set_context(void *context)
 213 {
 214 #if defined(GLX_USE_TLS)
 215    _glapi_tls_Context = context;
 216 #elif defined(THREADS)
 217    _glthread_SetTSD(&ContextTSD, context);
 218    _glapi_Context = (ThreadSafe) ? NULL : context;
 219 #else
 220    _glapi_Context = context;
 221 #endif
 222 }
 223
 224
 225
 226 /**
 227  * Get the current context pointer for this thread.
 228  * The context pointer is an opaque type which should be cast from
 229  * void to the real context pointer type.
 230  */
 231 PUBLIC void *
 232 _glapi_get_context(void)
 233 {
 234 #if defined(GLX_USE_TLS)
 235    return _glapi_tls_Context;
 236 #elif defined(THREADS)
 237    return (ThreadSafe) ? _glthread_GetTSD(&ContextTSD) : _glapi_Context;
 238 #else
 239    return _glapi_Context;
 240 #endif
 241 }
 242
 243
 244
 245 /**
 246  * Set the global or per-thread dispatch table pointer.
 247  * If the dispatch parameter is NULL we'll plug in the no-op dispatch
 248  * table (__glapi_noop_table).
 249  */
 250 PUBLIC void
 251 _glapi_set_dispatch(struct _glapi_table *dispatch)
 252 {
 253    init_glapi_relocs_once();
 254
 255    if (dispatch == NULL) {
 256       /* use the no-op functions */
 257       dispatch = (struct _glapi_table *) __glapi_noop_table;
 258    }
 259 #ifdef DEBUG
 260    else {
 261       _glapi_check_table_not_null(dispatch);
 262       _glapi_check_table(dispatch);
 263    }
 264 #endif
 265
 266 #if defined(GLX_USE_TLS)
 267    _glapi_tls_Dispatch = dispatch;
 268 #elif defined(THREADS)
 269    _glthread_SetTSD(&_gl_DispatchTSD, (void *) dispatch);
 270    _glapi_Dispatch = (ThreadSafe) ? NULL : dispatch;
 271 #else
 272    _glapi_Dispatch = dispatch;
 273 #endif
 274 }
 275
 276
 277
 278 /**
 279  * Return pointer to current dispatch table for calling thread.
 280  */
 281 PUBLIC struct _glapi_table *
 282 _glapi_get_dispatch(void)
 283 {
 284 #if defined(GLX_USE_TLS)
 285    return _glapi_tls_Dispatch;
 286 #elif defined(THREADS)
 287    return (ThreadSafe)
 288      ? (struct _glapi_table *) _glthread_GetTSD(&_gl_DispatchTSD)
 289      : _glapi_Dispatch;
 290 #else
 291    return _glapi_Dispatch;
 292 #endif
 293 }