2 * Mesa 3-D graphics library
4 * Copyright (C) 1999-2008 Brian Paul All Rights Reserved.
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7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
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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:
13 * The above copyright notice and this permission notice shall be included
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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.
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.
38 * NOTE: There are no dependencies on Mesa in this code.
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.
51 #include "c11/threads.h"
52 #include "u_current.h"
54 #ifndef MAPI_MODE_UTIL
61 extern void init_glapi_relocs_once(void);
62 extern void (*__glapi_noop_table
[])(void);
64 #define table_noop_array __glapi_noop_table
65 #define stub_init_once() init_glapi_relocs_once()
70 * \name Current dispatch and current context control variables
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
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.
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.
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.
100 #if defined(GLX_USE_TLS)
102 __thread
struct _glapi_table
*u_current_table
103 __attribute__((tls_model("initial-exec")))
104 = (struct _glapi_table
*) table_noop_array
;
106 __thread
void *u_current_context
107 __attribute__((tls_model("initial-exec")));
111 struct _glapi_table
*u_current_table
=
112 (struct _glapi_table
*) table_noop_array
;
113 void *u_current_context
;
115 tss_t u_current_table_tsd
;
116 static tss_t u_current_context_tsd
;
117 static int ThreadSafe
;
119 #endif /* defined(GLX_USE_TLS) */
124 u_current_destroy(void)
126 #if !defined(GLX_USE_TLS)
127 tss_delete(u_current_table_tsd
);
128 tss_delete(u_current_context_tsd
);
133 #if !defined(GLX_USE_TLS)
136 u_current_init_tsd(void)
138 tss_create(&u_current_table_tsd
, NULL
);
139 tss_create(&u_current_context_tsd
, NULL
);
143 * Mutex for multithread check.
145 static mtx_t ThreadCheckMutex
= _MTX_INITIALIZER_NP
;
149 typedef DWORD thread_id
;
151 typedef thrd_t thread_id
;
155 static inline thread_id
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.
166 return GetCurrentThreadId();
168 return thrd_current();
174 thread_id_equal(thread_id t1
, thread_id t2
)
179 return thrd_equal(t1
, t2
);
185 * We should call this periodically from a function such as glXMakeCurrent
186 * in order to test if multiple threads are being used.
191 static thread_id knownID
;
192 static int firstCall
= 1;
197 mtx_lock(&ThreadCheckMutex
);
199 u_current_init_tsd();
201 knownID
= get_thread_id();
204 else if (!thread_id_equal(knownID
, get_thread_id())) {
206 u_current_set_table(NULL
);
207 u_current_set_context(NULL
);
209 mtx_unlock(&ThreadCheckMutex
);
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.
229 u_current_set_context(const void *ptr
)
233 #if defined(GLX_USE_TLS)
234 u_current_context
= (void *) ptr
;
236 tss_set(u_current_context_tsd
, (void *) ptr
);
237 u_current_context
= (ThreadSafe
) ? NULL
: (void *) ptr
;
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.
247 u_current_get_context_internal(void)
249 #if defined(GLX_USE_TLS)
250 return u_current_context
;
252 return ThreadSafe
? tss_get(u_current_context_tsd
) : u_current_context
;
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).
262 u_current_set_table(const struct _glapi_table
*tbl
)
269 tbl
= (const struct _glapi_table
*) table_noop_array
;
271 #if defined(GLX_USE_TLS)
272 u_current_table
= (struct _glapi_table
*) tbl
;
274 tss_set(u_current_table_tsd
, (void *) tbl
);
275 u_current_table
= (ThreadSafe
) ? NULL
: (void *) tbl
;
280 * Return pointer to current dispatch table for calling thread.
282 struct _glapi_table
*
283 u_current_get_table_internal(void)
285 #if defined(GLX_USE_TLS)
286 return u_current_table
;
289 return (struct _glapi_table
*) tss_get(u_current_table_tsd
);
291 return (struct _glapi_table
*) u_current_table
;