+++ /dev/null
-/* Copyright (C) 2003-2014 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- Contributed by Paul Mackerras <paulus@au.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, see
- <http://www.gnu.org/licenses/>. */
-
-#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;
-
- __asm __volatile (__lll_rel_instr);
- *once_control = 0;
- lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
-}
-
-
-int
-__pthread_once (pthread_once_t *once_control, void (*init_routine) (void))
-{
- for (;;)
- {
- int oldval;
- int newval;
- int tmp;
-
- /* Pseudo code:
- newval = __fork_generation | 1;
- oldval = *once_control;
- if ((oldval & 2) == 0)
- *once_control = newval;
- Do this atomically with an acquire barrier.
- */
- newval = __fork_generation | 1;
- __asm __volatile ("1: lwarx %0,0,%3" MUTEX_HINT_ACQ "\n"
- " andi. %1,%0,2\n"
- " bne 2f\n"
- " stwcx. %4,0,%3\n"
- " bne 1b\n"
- "2: " __lll_acq_instr
- : "=&r" (oldval), "=&r" (tmp), "=m" (*once_control)
- : "r" (once_control), "r" (newval), "m" (*once_control)
- : "cr0");
-
- /* Check if the initializer has already been done. */
- if ((oldval & 2) != 0)
- return 0;
-
- /* Check if another thread already runs the initializer. */
- if ((oldval & 1) == 0)
- break;
-
- /* Check whether the initializer execution was interrupted by a fork. */
- if (oldval != newval)
- break;
-
- /* Same generation, some other thread was faster. Wait. */
- lll_futex_wait (once_control, oldval, LLL_PRIVATE);
- }
-
-
- /* 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 to take the bottom 2 bits from 01 to 10.
- A release barrier is needed to ensure memory written by init_routine
- is seen in other threads before *once_control changes. */
- int tmp;
- __asm __volatile (__lll_rel_instr "\n"
- "1: lwarx %0,0,%2" MUTEX_HINT_REL "\n"
- " addi %0,%0,1\n"
- " stwcx. %0,0,%2\n"
- " bne- 1b"
- : "=&b" (tmp), "=m" (*once_control)
- : "r" (once_control), "m" (*once_control)
- : "cr0");
-
- /* Wake up all other threads. */
- lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
-
- return 0;
-}
-weak_alias (__pthread_once, pthread_once)
-hidden_def (__pthread_once)