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/* Copyright (C) 2003 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include "pthreadP.h"
#include <lowlevellock.h>
unsigned long int __fork_generation attribute_hidden;
static void
clear_once_control (void *arg)
{
pthread_once_t *once_control = (pthread_once_t *) arg;
*once_control = 0;
lll_futex_wake (once_control, INT_MAX);
}
int
__pthread_once (once_control, init_routine)
pthread_once_t *once_control;
void (*init_routine) (void);
{
while (1)
{
int oldval;
int newval;
/* Pseudo code:
oldval = *once_control;
if ((oldval & 2) == 0)
{
newval = (oldval & 3) | __fork_generation | 1;
*once_control = newval;
}
Do this atomically. */
__asm __volatile (" l %1,%0\n"
"0: lhi %2,2\n"
" tml %1,2\n"
" jnz 1f\n"
" nr %2,%1\n"
" ahi %2,1\n"
" o %2,%3\n"
" cs %1,%2,%0\n"
" jl 0b\n"
"1:"
: "=Q" (*once_control), "=&d" (oldval), "=&d" (newval)
: "m" (__fork_generation), "m" (*once_control)
: "cc" );
/* Check if the initialized has already been done. */
if ((oldval & 2) != 0)
break;
/* Check if another thread already runs the initializer. */
if ((oldval & 1) != 0)
{
/* Check whether the initializer execution was interrupted
by a fork. */
if (((oldval ^ newval) & -4) == 0)
{
/* Same generation, some other thread was faster. Wait. */
lll_futex_wait (once_control, newval);
continue;
}
}
/* This thread is the first here. Do the initialization.
Register a cleanup handler so that in case the thread gets
interrupted the initialization can be restarted. */
pthread_cleanup_push (clear_once_control, once_control);
init_routine ();
pthread_cleanup_pop (0);
/* Add one to *once_control. */
__asm __volatile (" l %1,%0\n"
"0: lr %2,%1\n"
" ahi %2,1\n"
" cs %1,%2,%0\n"
" jl 0b\n"
: "=Q" (*once_control), "=&d" (oldval), "=&d" (newval)
: "m" (*once_control) : "cc" );
/* Wake up all other threads. */
lll_futex_wake (once_control, INT_MAX);
break;
}
return 0;
}
weak_alias (__pthread_once, pthread_once)
strong_alias (__pthread_once, __pthread_once_internal)
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