1 /*
2 * Mesa 3-D graphics library
3 *
4 * Copyright (C) 1999-2008 Brian Paul All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included
14 * in all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
17 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * 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 "c11/threads.h"
52 #include "util/u_thread.h"
53 #include "u_current.h"
54
55 #ifndef MAPI_MODE_UTIL
56
57 #include "table.h"
58 #include "stub.h"
59
60 #else
61
62 extern void init_glapi_relocs_once(void);
63 extern void (*__glapi_noop_table[])(void);
64
65 #define table_noop_array __glapi_noop_table
66 #define stub_init_once() init_glapi_relocs_once()
67
68 #endif
69
70 /**
71 * \name Current dispatch and current context control variables
72 *
73 * Depending on whether or not multithreading is support, and the type of
74 * support available, several variables are used to store the current context
75 * pointer and the current dispatch table pointer. In the non-threaded case,
76 * the variables \c _glapi_Dispatch and \c _glapi_Context are used for this
77 * purpose.
78 *
79 * In the "normal" threaded case, the variables \c _glapi_Dispatch and
80 * \c _glapi_Context will be \c NULL if an application is detected as being
81 * multithreaded. Single-threaded applications will use \c _glapi_Dispatch
82 * and \c _glapi_Context just like the case without any threading support.
83 * When \c _glapi_Dispatch and \c _glapi_Context are \c NULL, the thread state
84 * data \c _gl_DispatchTSD and \c ContextTSD are used. Drivers and the
85 * static dispatch functions access these variables via \c _glapi_get_dispatch
86 * and \c _glapi_get_context.
87 *
88 * There is a race condition in setting \c _glapi_Dispatch to \c NULL. It is
89 * possible for the original thread to be setting it at the same instant a new
90 * thread, perhaps running on a different processor, is clearing it. Because
91 * of that, \c ThreadSafe, which can only ever be changed to \c GL_TRUE, is
92 * used to determine whether or not the application is multithreaded.
93 *
94 * In the TLS case, the variables \c _glapi_Dispatch and \c _glapi_Context are
95 * hardcoded to \c NULL. Instead the TLS variables \c _glapi_tls_Dispatch and
96 * \c _glapi_tls_Context are used. Having \c _glapi_Dispatch and
97 * \c _glapi_Context be hardcoded to \c NULL maintains binary compatability
98 * between TLS enabled loaders and non-TLS DRI drivers.
99 */
100 /*@{*/
101 #if defined(USE_ELF_TLS)
102
103 __THREAD_INITIAL_EXEC struct _glapi_table *u_current_table
104 = (struct _glapi_table *) table_noop_array;
105
106 __THREAD_INITIAL_EXEC void *u_current_context;
107
108 #else
109
110 struct _glapi_table *u_current_table =
111 (struct _glapi_table *) table_noop_array;
112 void *u_current_context;
113
114 tss_t u_current_table_tsd;
115 static tss_t u_current_context_tsd;
116 static int ThreadSafe;
117
118 #endif /* defined(USE_ELF_TLS) */
119 /*@}*/
120
121
122 void
u_current_destroy(void)123 u_current_destroy(void)
124 {
125 #if !defined(USE_ELF_TLS)
126 tss_delete(u_current_table_tsd);
127 tss_delete(u_current_context_tsd);
128 #endif
129 }
130
131
132 #if !defined(USE_ELF_TLS)
133
134 static void
u_current_init_tsd(void)135 u_current_init_tsd(void)
136 {
137 tss_create(&u_current_table_tsd, NULL);
138 tss_create(&u_current_context_tsd, NULL);
139 }
140
141 /**
142 * Mutex for multithread check.
143 */
144 static mtx_t ThreadCheckMutex = _MTX_INITIALIZER_NP;
145
146 static thread_id knownID;
147
148 /**
149 * We should call this periodically from a function such as glXMakeCurrent
150 * in order to test if multiple threads are being used.
151 */
152 void
u_current_init(void)153 u_current_init(void)
154 {
155 static int firstCall = 1;
156
157 if (ThreadSafe)
158 return;
159
160 mtx_lock(&ThreadCheckMutex);
161 if (firstCall) {
162 u_current_init_tsd();
163
164 knownID = util_get_thread_id();
165 firstCall = 0;
166 }
167 else if (!util_thread_id_equal(knownID, util_get_thread_id())) {
168 ThreadSafe = 1;
169 u_current_set_table(NULL);
170 u_current_set_context(NULL);
171 }
172 mtx_unlock(&ThreadCheckMutex);
173 }
174
175 #else
176
177 void
u_current_init(void)178 u_current_init(void)
179 {
180 }
181
182 #endif
183
184
185
186 /**
187 * Set the current context pointer for this thread.
188 * The context pointer is an opaque type which should be cast to
189 * void from the real context pointer type.
190 */
191 void
u_current_set_context(const void * ptr)192 u_current_set_context(const void *ptr)
193 {
194 u_current_init();
195
196 #if defined(USE_ELF_TLS)
197 u_current_context = (void *) ptr;
198 #else
199 tss_set(u_current_context_tsd, (void *) ptr);
200 u_current_context = (ThreadSafe) ? NULL : (void *) ptr;
201 #endif
202 }
203
204 /**
205 * Get the current context pointer for this thread.
206 * The context pointer is an opaque type which should be cast from
207 * void to the real context pointer type.
208 */
209 void *
u_current_get_context_internal(void)210 u_current_get_context_internal(void)
211 {
212 #if defined(USE_ELF_TLS)
213 return u_current_context;
214 #else
215 if (ThreadSafe)
216 return tss_get(u_current_context_tsd);
217 else if (!util_thread_id_equal(knownID, util_get_thread_id()))
218 return NULL;
219 else
220 return u_current_context;
221 #endif
222 }
223
224 /**
225 * Set the global or per-thread dispatch table pointer.
226 * If the dispatch parameter is NULL we'll plug in the no-op dispatch
227 * table (__glapi_noop_table).
228 */
229 void
u_current_set_table(const struct _glapi_table * tbl)230 u_current_set_table(const struct _glapi_table *tbl)
231 {
232 u_current_init();
233
234 stub_init_once();
235
236 if (!tbl)
237 tbl = (const struct _glapi_table *) table_noop_array;
238
239 #if defined(USE_ELF_TLS)
240 u_current_table = (struct _glapi_table *) tbl;
241 #else
242 tss_set(u_current_table_tsd, (void *) tbl);
243 u_current_table = (ThreadSafe) ? NULL : (void *) tbl;
244 #endif
245 }
246
247 /**
248 * Return pointer to current dispatch table for calling thread.
249 */
250 struct _glapi_table *
u_current_get_table_internal(void)251 u_current_get_table_internal(void)
252 {
253 #if defined(USE_ELF_TLS)
254 return u_current_table;
255 #else
256 if (ThreadSafe)
257 return (struct _glapi_table *) tss_get(u_current_table_tsd);
258 else if (!util_thread_id_equal(knownID, util_get_thread_id()))
259 return (struct _glapi_table *) table_noop_array;
260 else
261 return (struct _glapi_table *) u_current_table;
262 #endif
263 }
264