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
62extern void init_glapi_relocs_once(void);
63extern 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#if defined(__NetBSD__)
105    = NULL; /* non-zero initializers not supported with dlopen */
106#else
107    = (struct _glapi_table *) table_noop_array;
108#endif
109
110__THREAD_INITIAL_EXEC void *u_current_context;
111
112#else
113
114struct _glapi_table *u_current_table =
115   (struct _glapi_table *) table_noop_array;
116void *u_current_context;
117
118tss_t u_current_table_tsd;
119static tss_t u_current_context_tsd;
120static int ThreadSafe;
121
122#endif /* defined(USE_ELF_TLS) */
123/*@}*/
124
125
126void
127u_current_destroy(void)
128{
129#if !defined(USE_ELF_TLS)
130   tss_delete(u_current_table_tsd);
131   tss_delete(u_current_context_tsd);
132#endif
133}
134
135
136#if !defined(USE_ELF_TLS)
137
138static void
139u_current_init_tsd(void)
140{
141   tss_create(&u_current_table_tsd, NULL);
142   tss_create(&u_current_context_tsd, NULL);
143}
144
145/**
146 * Mutex for multithread check.
147 */
148static mtx_t ThreadCheckMutex = _MTX_INITIALIZER_NP;
149
150static thread_id knownID;
151
152/**
153 * We should call this periodically from a function such as glXMakeCurrent
154 * in order to test if multiple threads are being used.
155 */
156void
157u_current_init(void)
158{
159   static int firstCall = 1;
160
161   if (ThreadSafe)
162      return;
163
164   mtx_lock(&ThreadCheckMutex);
165   if (firstCall) {
166      u_current_init_tsd();
167
168      knownID = util_get_thread_id();
169      firstCall = 0;
170   }
171   else if (!util_thread_id_equal(knownID, util_get_thread_id())) {
172      ThreadSafe = 1;
173      u_current_set_table(NULL);
174      u_current_set_context(NULL);
175   }
176   mtx_unlock(&ThreadCheckMutex);
177}
178
179#else
180
181void
182u_current_init(void)
183{
184}
185
186#endif
187
188
189
190/**
191 * Set the current context pointer for this thread.
192 * The context pointer is an opaque type which should be cast to
193 * void from the real context pointer type.
194 */
195void
196u_current_set_context(const void *ptr)
197{
198   u_current_init();
199
200#if defined(USE_ELF_TLS)
201   u_current_context = (void *) ptr;
202#else
203   tss_set(u_current_context_tsd, (void *) ptr);
204   u_current_context = (ThreadSafe) ? NULL : (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_context_internal(void)
215{
216#if defined(USE_ELF_TLS)
217   return u_current_context;
218#else
219   if (ThreadSafe)
220      return tss_get(u_current_context_tsd);
221   else if (!util_thread_id_equal(knownID, util_get_thread_id()))
222      return NULL;
223   else
224      return u_current_context;
225#endif
226}
227
228/**
229 * Set the global or per-thread dispatch table pointer.
230 * If the dispatch parameter is NULL we'll plug in the no-op dispatch
231 * table (__glapi_noop_table).
232 */
233void
234u_current_set_table(const struct _glapi_table *tbl)
235{
236   u_current_init();
237
238   stub_init_once();
239
240   if (!tbl)
241      tbl = (const struct _glapi_table *) table_noop_array;
242
243#if defined(USE_ELF_TLS)
244   u_current_table = (struct _glapi_table *) tbl;
245#else
246   tss_set(u_current_table_tsd, (void *) tbl);
247   u_current_table = (ThreadSafe) ? NULL : (void *) tbl;
248#endif
249}
250
251/**
252 * Return pointer to current dispatch table for calling thread.
253 */
254struct _glapi_table *
255u_current_get_table_internal(void)
256{
257#if defined(USE_ELF_TLS)
258#  if defined(__NetBSD__)
259   return (likely(u_current_table) ? u_current_table : (struct _glapi_table *) table_noop_array);
260#  else
261   return u_current_table;
262#  endif
263#else
264   if (ThreadSafe)
265      return (struct _glapi_table *) tss_get(u_current_table_tsd);
266   else if (!util_thread_id_equal(knownID, util_get_thread_id()))
267      return (struct _glapi_table *) table_noop_array;
268   else
269      return (struct _glapi_table *) u_current_table;
270#endif
271}
272