/*
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* Mesa 3-D graphics library
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*
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* Copyright (C) 1999-2008 Brian Paul All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* This file manages the OpenGL API dispatch layer.
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* The dispatch table (struct _glapi_table) is basically just a list
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* of function pointers.
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* There are functions to set/get the current dispatch table for the
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* current thread and to manage registration/dispatch of dynamically
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* added extension functions.
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*
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* It's intended that this file and the other glapi*.[ch] files are
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* flexible enough to be reused in several places: XFree86, DRI-
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* based libGL.so, and perhaps the SGI SI.
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*
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* NOTE: There are no dependencies on Mesa in this code.
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*
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* Versions (API changes):
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* 2000/02/23 - original version for Mesa 3.3 and XFree86 4.0
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* 2001/01/16 - added dispatch override feature for Mesa 3.5
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* 2002/06/28 - added _glapi_set_warning_func(), Mesa 4.1.
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* 2002/10/01 - _glapi_get_proc_address() will now generate new entrypoints
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* itself (using offset ~0). _glapi_add_entrypoint() can be
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* called afterward and it'll fill in the correct dispatch
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* offset. This allows DRI libGL to avoid probing for DRI
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* drivers! No changes to the public glapi interface.
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*/
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#include "c11/threads.h"
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#include "u_current.h"
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#ifndef MAPI_MODE_UTIL
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#include "table.h"
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#include "stub.h"
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#else
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extern void init_glapi_relocs_once(void);
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extern void (*__glapi_noop_table[])(void);
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#define table_noop_array __glapi_noop_table
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#define stub_init_once() init_glapi_relocs_once()
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#endif
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/**
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* \name Current dispatch and current context control variables
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*
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* Depending on whether or not multithreading is support, and the type of
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* support available, several variables are used to store the current context
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* pointer and the current dispatch table pointer. In the non-threaded case,
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* the variables \c _glapi_Dispatch and \c _glapi_Context are used for this
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* purpose.
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*
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* In the "normal" threaded case, the variables \c _glapi_Dispatch and
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* \c _glapi_Context will be \c NULL if an application is detected as being
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* multithreaded. Single-threaded applications will use \c _glapi_Dispatch
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* and \c _glapi_Context just like the case without any threading support.
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* When \c _glapi_Dispatch and \c _glapi_Context are \c NULL, the thread state
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* data \c _gl_DispatchTSD and \c ContextTSD are used. Drivers and the
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* static dispatch functions access these variables via \c _glapi_get_dispatch
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* and \c _glapi_get_context.
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*
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* There is a race condition in setting \c _glapi_Dispatch to \c NULL. It is
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* possible for the original thread to be setting it at the same instant a new
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* thread, perhaps running on a different processor, is clearing it. Because
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* of that, \c ThreadSafe, which can only ever be changed to \c GL_TRUE, is
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* used to determine whether or not the application is multithreaded.
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*
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* In the TLS case, the variables \c _glapi_Dispatch and \c _glapi_Context are
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* hardcoded to \c NULL. Instead the TLS variables \c _glapi_tls_Dispatch and
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* \c _glapi_tls_Context are used. Having \c _glapi_Dispatch and
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* \c _glapi_Context be hardcoded to \c NULL maintains binary compatability
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* between TLS enabled loaders and non-TLS DRI drivers.
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*/
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/*@{*/
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#if defined(GLX_USE_TLS)
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__thread struct _glapi_table *u_current_table
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__attribute__((tls_model("initial-exec")))
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= (struct _glapi_table *) table_noop_array;
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__thread void *u_current_context
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__attribute__((tls_model("initial-exec")));
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#else
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struct _glapi_table *u_current_table =
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(struct _glapi_table *) table_noop_array;
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void *u_current_context;
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tss_t u_current_table_tsd;
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static tss_t u_current_context_tsd;
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static int ThreadSafe;
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#endif /* defined(GLX_USE_TLS) */
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/*@}*/
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void
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u_current_destroy(void)
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{
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#if !defined(GLX_USE_TLS)
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tss_delete(u_current_table_tsd);
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tss_delete(u_current_context_tsd);
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#endif
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}
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#if !defined(GLX_USE_TLS)
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static void
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u_current_init_tsd(void)
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{
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tss_create(&u_current_table_tsd, NULL);
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tss_create(&u_current_context_tsd, NULL);
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}
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/**
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* Mutex for multithread check.
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*/
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static mtx_t ThreadCheckMutex = _MTX_INITIALIZER_NP;
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#ifdef _WIN32
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typedef DWORD thread_id;
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#else
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typedef thrd_t thread_id;
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#endif
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static inline thread_id
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get_thread_id(void)
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{
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/*
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* XXX: Callers of of this function assume it is a lightweight function.
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* But unfortunately C11's thrd_current() gives no such guarantees. In
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* fact, it's pretty hard to have a compliant implementation of
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* thrd_current() on Windows with such characteristics. So for now, we
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* side-step this mess and use Windows thread primitives directly here.
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*/
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#ifdef _WIN32
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return GetCurrentThreadId();
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#else
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return thrd_current();
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#endif
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}
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static inline int
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thread_id_equal(thread_id t1, thread_id t2)
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{
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#ifdef _WIN32
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return t1 == t2;
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#else
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return thrd_equal(t1, t2);
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#endif
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}
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/**
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* We should call this periodically from a function such as glXMakeCurrent
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* in order to test if multiple threads are being used.
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*/
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void
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u_current_init(void)
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{
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static thread_id knownID;
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static int firstCall = 1;
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if (ThreadSafe)
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return;
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mtx_lock(&ThreadCheckMutex);
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if (firstCall) {
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u_current_init_tsd();
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knownID = get_thread_id();
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firstCall = 0;
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}
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else if (!thread_id_equal(knownID, get_thread_id())) {
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ThreadSafe = 1;
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u_current_set_table(NULL);
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u_current_set_context(NULL);
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}
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mtx_unlock(&ThreadCheckMutex);
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}
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#else
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void
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u_current_init(void)
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{
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}
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#endif
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/**
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* Set the current context pointer for this thread.
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* The context pointer is an opaque type which should be cast to
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* void from the real context pointer type.
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*/
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void
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u_current_set_context(const void *ptr)
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{
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u_current_init();
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#if defined(GLX_USE_TLS)
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u_current_context = (void *) ptr;
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#else
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tss_set(u_current_context_tsd, (void *) ptr);
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u_current_context = (ThreadSafe) ? NULL : (void *) ptr;
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#endif
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}
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/**
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* Get the current context pointer for this thread.
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* The context pointer is an opaque type which should be cast from
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* void to the real context pointer type.
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*/
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void *
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u_current_get_context_internal(void)
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{
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#if defined(GLX_USE_TLS)
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return u_current_context;
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#else
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return ThreadSafe ? tss_get(u_current_context_tsd) : u_current_context;
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#endif
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}
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/**
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* Set the global or per-thread dispatch table pointer.
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* If the dispatch parameter is NULL we'll plug in the no-op dispatch
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* table (__glapi_noop_table).
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*/
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void
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u_current_set_table(const struct _glapi_table *tbl)
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{
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u_current_init();
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stub_init_once();
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if (!tbl)
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tbl = (const struct _glapi_table *) table_noop_array;
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#if defined(GLX_USE_TLS)
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u_current_table = (struct _glapi_table *) tbl;
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#else
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tss_set(u_current_table_tsd, (void *) tbl);
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u_current_table = (ThreadSafe) ? NULL : (void *) tbl;
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#endif
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}
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/**
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* Return pointer to current dispatch table for calling thread.
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*/
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struct _glapi_table *
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u_current_get_table_internal(void)
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{
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#if defined(GLX_USE_TLS)
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return u_current_table;
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#else
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if (ThreadSafe)
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return (struct _glapi_table *) tss_get(u_current_table_tsd);
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else
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return (struct _glapi_table *) u_current_table;
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#endif
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}
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