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