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 "u_current.h"
53
54 #ifndef MAPI_MODE_UTIL
55
56 #include "table.h"
57 #include "stub.h"
58
59 #else
60
61 extern void init_glapi_relocs_once(void);
62 extern 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 _glapi_table *u_current_table
103 __attribute__((tls_model("initial-exec")))
104 = (struct _glapi_table *) table_noop_array;
105
106 __thread void *u_current_context
107 __attribute__((tls_model("initial-exec")));
108
109 #else
110
111 struct _glapi_table *u_current_table =
112 (struct _glapi_table *) table_noop_array;
113 void *u_current_context;
114
115 tss_t u_current_table_tsd;
116 static tss_t u_current_context_tsd;
117 static int ThreadSafe;
118
119 #endif /* defined(GLX_USE_TLS) */
120 /*@}*/
121
122
123 void
u_current_destroy(void)124 u_current_destroy(void)
125 {
126 #if !defined(GLX_USE_TLS)
127 tss_delete(u_current_table_tsd);
128 tss_delete(u_current_context_tsd);
129 #endif
130 }
131
132
133 #if !defined(GLX_USE_TLS)
134
135 static void
u_current_init_tsd(void)136 u_current_init_tsd(void)
137 {
138 tss_create(&u_current_table_tsd, NULL);
139 tss_create(&u_current_context_tsd, NULL);
140 }
141
142 /**
143 * Mutex for multithread check.
144 */
145 static mtx_t ThreadCheckMutex = _MTX_INITIALIZER_NP;
146
147
148 #ifdef _WIN32
149 typedef DWORD thread_id;
150 #else
151 typedef thrd_t thread_id;
152 #endif
153
154
155 static inline thread_id
get_thread_id(void)156 get_thread_id(void)
157 {
158 /*
159 * XXX: Callers of of this function assume it is a lightweight function.
160 * But unfortunately C11's thrd_current() gives no such guarantees. In
161 * fact, it's pretty hard to have a compliant implementation of
162 * thrd_current() on Windows with such characteristics. So for now, we
163 * side-step this mess and use Windows thread primitives directly here.
164 */
165 #ifdef _WIN32
166 return GetCurrentThreadId();
167 #else
168 return thrd_current();
169 #endif
170 }
171
172
173 static inline int
thread_id_equal(thread_id t1,thread_id t2)174 thread_id_equal(thread_id t1, thread_id t2)
175 {
176 #ifdef _WIN32
177 return t1 == t2;
178 #else
179 return thrd_equal(t1, t2);
180 #endif
181 }
182
183
184 /**
185 * We should call this periodically from a function such as glXMakeCurrent
186 * in order to test if multiple threads are being used.
187 */
188 void
u_current_init(void)189 u_current_init(void)
190 {
191 static thread_id knownID;
192 static int firstCall = 1;
193
194 if (ThreadSafe)
195 return;
196
197 mtx_lock(&ThreadCheckMutex);
198 if (firstCall) {
199 u_current_init_tsd();
200
201 knownID = get_thread_id();
202 firstCall = 0;
203 }
204 else if (!thread_id_equal(knownID, get_thread_id())) {
205 ThreadSafe = 1;
206 u_current_set_table(NULL);
207 u_current_set_context(NULL);
208 }
209 mtx_unlock(&ThreadCheckMutex);
210 }
211
212 #else
213
214 void
u_current_init(void)215 u_current_init(void)
216 {
217 }
218
219 #endif
220
221
222
223 /**
224 * Set the current context pointer for this thread.
225 * The context pointer is an opaque type which should be cast to
226 * void from the real context pointer type.
227 */
228 void
u_current_set_context(const void * ptr)229 u_current_set_context(const void *ptr)
230 {
231 u_current_init();
232
233 #if defined(GLX_USE_TLS)
234 u_current_context = (void *) ptr;
235 #else
236 tss_set(u_current_context_tsd, (void *) ptr);
237 u_current_context = (ThreadSafe) ? NULL : (void *) ptr;
238 #endif
239 }
240
241 /**
242 * Get the current context pointer for this thread.
243 * The context pointer is an opaque type which should be cast from
244 * void to the real context pointer type.
245 */
246 void *
u_current_get_context_internal(void)247 u_current_get_context_internal(void)
248 {
249 #if defined(GLX_USE_TLS)
250 return u_current_context;
251 #else
252 return ThreadSafe ? tss_get(u_current_context_tsd) : u_current_context;
253 #endif
254 }
255
256 /**
257 * Set the global or per-thread dispatch table pointer.
258 * If the dispatch parameter is NULL we'll plug in the no-op dispatch
259 * table (__glapi_noop_table).
260 */
261 void
u_current_set_table(const struct _glapi_table * tbl)262 u_current_set_table(const struct _glapi_table *tbl)
263 {
264 u_current_init();
265
266 stub_init_once();
267
268 if (!tbl)
269 tbl = (const struct _glapi_table *) table_noop_array;
270
271 #if defined(GLX_USE_TLS)
272 u_current_table = (struct _glapi_table *) tbl;
273 #else
274 tss_set(u_current_table_tsd, (void *) tbl);
275 u_current_table = (ThreadSafe) ? NULL : (void *) tbl;
276 #endif
277 }
278
279 /**
280 * Return pointer to current dispatch table for calling thread.
281 */
282 struct _glapi_table *
u_current_get_table_internal(void)283 u_current_get_table_internal(void)
284 {
285 #if defined(GLX_USE_TLS)
286 return u_current_table;
287 #else
288 if (ThreadSafe)
289 return (struct _glapi_table *) tss_get(u_current_table_tsd);
290 else
291 return (struct _glapi_table *) u_current_table;
292 #endif
293 }
294