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#include "u_current.h"
52#include "u_thread.h"
53
54#ifndef MAPI_MODE_UTIL
55
56#include "table.h"
57#include "stub.h"
58
59#else
60
61extern void init_glapi_relocs_once(void);
62extern void (*__glapi_noop_table[])(void);
63
64#define table_noop_array __glapi_noop_table
65#define stub_init_once() init_glapi_relocs_once()
66
67#endif
68
69/**
70 * \name Current dispatch and current context control variables
71 *
72 * Depending on whether or not multithreading is support, and the type of
73 * support available, several variables are used to store the current context
74 * pointer and the current dispatch table pointer.  In the non-threaded case,
75 * the variables \c _glapi_Dispatch and \c _glapi_Context are used for this
76 * purpose.
77 *
78 * In the "normal" threaded case, the variables \c _glapi_Dispatch and
79 * \c _glapi_Context will be \c NULL if an application is detected as being
80 * multithreaded.  Single-threaded applications will use \c _glapi_Dispatch
81 * and \c _glapi_Context just like the case without any threading support.
82 * When \c _glapi_Dispatch and \c _glapi_Context are \c NULL, the thread state
83 * data \c _gl_DispatchTSD and \c ContextTSD are used.  Drivers and the
84 * static dispatch functions access these variables via \c _glapi_get_dispatch
85 * and \c _glapi_get_context.
86 *
87 * There is a race condition in setting \c _glapi_Dispatch to \c NULL.  It is
88 * possible for the original thread to be setting it at the same instant a new
89 * thread, perhaps running on a different processor, is clearing it.  Because
90 * of that, \c ThreadSafe, which can only ever be changed to \c GL_TRUE, is
91 * used to determine whether or not the application is multithreaded.
92 *
93 * In the TLS case, the variables \c _glapi_Dispatch and \c _glapi_Context are
94 * hardcoded to \c NULL.  Instead the TLS variables \c _glapi_tls_Dispatch and
95 * \c _glapi_tls_Context are used.  Having \c _glapi_Dispatch and
96 * \c _glapi_Context be hardcoded to \c NULL maintains binary compatability
97 * between TLS enabled loaders and non-TLS DRI drivers.
98 */
99/*@{*/
100#if defined(GLX_USE_TLS)
101
102__thread struct mapi_table *u_current_table
103    __attribute__((tls_model("initial-exec")))
104    = (struct mapi_table *) table_noop_array;
105
106__thread void *u_current_user
107    __attribute__((tls_model("initial-exec")));
108
109#else
110
111struct mapi_table *u_current_table =
112   (struct mapi_table *) table_noop_array;
113void *u_current_user;
114
115#ifdef THREADS
116struct u_tsd u_current_table_tsd;
117static struct u_tsd u_current_user_tsd;
118static int ThreadSafe;
119#endif /* THREADS */
120
121#endif /* defined(GLX_USE_TLS) */
122/*@}*/
123
124
125void
126u_current_destroy(void)
127{
128#if defined(THREADS) && defined(WIN32)
129   u_tsd_destroy(&u_current_table_tsd);
130   u_tsd_destroy(&u_current_user_tsd);
131#endif
132}
133
134
135#if defined(THREADS) && !defined(GLX_USE_TLS)
136
137static void
138u_current_init_tsd(void)
139{
140   u_tsd_init(&u_current_table_tsd);
141   u_tsd_init(&u_current_user_tsd);
142}
143
144/**
145 * Mutex for multithread check.
146 */
147u_mutex_declare_static(ThreadCheckMutex);
148
149/**
150 * We should call this periodically from a function such as glXMakeCurrent
151 * in order to test if multiple threads are being used.
152 */
153void
154u_current_init(void)
155{
156   static unsigned long knownID;
157   static int firstCall = 1;
158
159   if (ThreadSafe)
160      return;
161
162   u_mutex_lock(ThreadCheckMutex);
163   if (firstCall) {
164      u_current_init_tsd();
165
166      knownID = u_thread_self();
167      firstCall = 0;
168   }
169   else if (knownID != u_thread_self()) {
170      ThreadSafe = 1;
171      u_current_set(NULL);
172      u_current_set_user(NULL);
173   }
174   u_mutex_unlock(ThreadCheckMutex);
175}
176
177#else
178
179void
180u_current_init(void)
181{
182}
183
184#endif
185
186
187
188/**
189 * Set the current context pointer for this thread.
190 * The context pointer is an opaque type which should be cast to
191 * void from the real context pointer type.
192 */
193void
194u_current_set_user(const void *ptr)
195{
196   u_current_init();
197
198#if defined(GLX_USE_TLS)
199   u_current_user = (void *) ptr;
200#elif defined(THREADS)
201   u_tsd_set(&u_current_user_tsd, (void *) ptr);
202   u_current_user = (ThreadSafe) ? NULL : (void *) ptr;
203#else
204   u_current_user = (void *) ptr;
205#endif
206}
207
208/**
209 * Get the current context pointer for this thread.
210 * The context pointer is an opaque type which should be cast from
211 * void to the real context pointer type.
212 */
213void *
214u_current_get_user_internal(void)
215{
216#if defined(GLX_USE_TLS)
217   return u_current_user;
218#elif defined(THREADS)
219   return (ThreadSafe)
220      ? u_tsd_get(&u_current_user_tsd)
221      : u_current_user;
222#else
223   return u_current_user;
224#endif
225}
226
227/**
228 * Set the global or per-thread dispatch table pointer.
229 * If the dispatch parameter is NULL we'll plug in the no-op dispatch
230 * table (__glapi_noop_table).
231 */
232void
233u_current_set(const struct mapi_table *tbl)
234{
235   u_current_init();
236
237   stub_init_once();
238
239   if (!tbl)
240      tbl = (const struct mapi_table *) table_noop_array;
241
242#if defined(GLX_USE_TLS)
243   u_current_table = (struct mapi_table *) tbl;
244#elif defined(THREADS)
245   u_tsd_set(&u_current_table_tsd, (void *) tbl);
246   u_current_table = (ThreadSafe) ? NULL : (void *) tbl;
247#else
248   u_current_table = (struct mapi_table *) tbl;
249#endif
250}
251
252/**
253 * Return pointer to current dispatch table for calling thread.
254 */
255struct mapi_table *
256u_current_get_internal(void)
257{
258#if defined(GLX_USE_TLS)
259   return u_current_table;
260#elif defined(THREADS)
261   return (struct mapi_table *) ((ThreadSafe) ?
262         u_tsd_get(&u_current_table_tsd) : (void *) u_current_table);
263#else
264   return u_current_table;
265#endif
266}
267