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Support for one-time initialization functions. (#69668, Sebastian

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2003-07-09  Matthias Clasen  <maclas@gmx.de>

	Support for one-time initialization functions.  (#69668, Sebastian Wilhelmi)

	* configure.in: Check whether double checked locking is safe, define g_once() in
	glibconfig.h accordingly.
	* glib/gthread.h: Add GOnce, GOnceStatus, G_ONCE_INIT and g_once_impl.
	* glib/gthread.c (g_once_impl): Fallback implementation using a mutex if double checked
	locking is unsafe.
	* tests/thread-test.c: Add tests for g_once().
This commit is contained in:
Matthias Clasen
2003-07-08 23:43:48 +00:00
committed by Matthias Clasen
parent 238c7c368b
commit 876f907863
12 changed files with 329 additions and 11 deletions
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52
glib/gthread.c
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@@ -1,7 +1,7 @@
/* GLIB - Library of useful routines for C programming
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* gmutex.c: MT safety related functions
* gthread.c: MT safety related functions
* Copyright 1998 Sebastian Wilhelmi; University of Karlsruhe
* Owen Taylor
*
@@ -148,7 +148,8 @@ GThreadFunctions g_thread_functions_for_glib_use = {
/* Local data */
static GMutex *g_mutex_protect_static_mutex_allocation = NULL;
static GMutex *g_once_mutex = NULL;
static GCond *g_once_cond = NULL;
static GPrivate *g_thread_specific_private = NULL;
static GSList *g_thread_all_threads = NULL;
static GSList *g_thread_free_indeces = NULL;
@@ -167,7 +168,8 @@ g_thread_init_glib (void)
*/
GRealThread* main_thread = (GRealThread*) g_thread_self ();
g_mutex_protect_static_mutex_allocation = g_mutex_new ();
g_once_mutex = g_mutex_new ();
g_once_cond = g_cond_new ();
_g_convert_thread_init ();
_g_rand_thread_init ();
@@ -198,6 +200,33 @@ g_thread_init_glib (void)
}
#endif /* G_THREADS_ENABLED */
gpointer
g_once_impl (GOnce *once,
GThreadFunc func,
gpointer arg)
{
g_mutex_lock (g_once_mutex);
while (once->status == G_ONCE_STATUS_PROGRESS)
g_cond_wait (g_once_cond, g_once_mutex);
if (once->status != G_ONCE_STATUS_READY)
{
once->status = G_ONCE_STATUS_PROGRESS;
g_mutex_unlock (g_once_mutex);
once->retval = func (arg);
g_mutex_lock (g_once_mutex);
once->status = G_ONCE_STATUS_READY;
g_cond_broadcast (g_once_cond);
}
g_mutex_unlock (g_once_mutex);
return once->retval;
}
void
g_static_mutex_init (GStaticMutex *mutex)
{
@@ -214,14 +243,23 @@ g_static_mutex_get_mutex_impl (GMutex** mutex)
if (!g_thread_supported ())
return NULL;
g_assert (g_mutex_protect_static_mutex_allocation);
g_assert (g_once_mutex);
g_mutex_lock (g_mutex_protect_static_mutex_allocation);
g_mutex_lock (g_once_mutex);
if (!(*mutex))
*mutex = g_mutex_new ();
{
GMutex *new_mutex = g_mutex_new ();
/* The following is a memory barrier to avoid the write
* to *new_mutex being reordered to after writing *mutex */
g_mutex_lock (new_mutex);
g_mutex_unlock (new_mutex);
*mutex = new_mutex;
}
g_mutex_unlock (g_mutex_protect_static_mutex_allocation);
g_mutex_unlock (g_once_mutex);
return *mutex;
}