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/* Copyright (C) 2003, 2004, 2007 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Jakub Jelinek <jakub@redhat.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; *once_control = 0; lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); } int attribute_protected __pthread_once (once_control, init_routine) pthread_once_t *once_control; void (*init_routine) (void); { while (1) { int oldval, val, newval; val = *once_control; do { /* Check if the initialized has already been done. */ if ((val & 2) != 0) return 0; oldval = val; newval = (oldval & 3) | __fork_generation | 1; val = atomic_compare_and_exchange_val_acq (once_control, newval, oldval); } while (__builtin_expect (val != oldval, 0)); /* 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, LLL_PRIVATE); 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. */ atomic_increment (once_control); /* Wake up all other threads. */ lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); break; } return 0; } weak_alias (__pthread_once, pthread_once) strong_alias (__pthread_once, __pthread_once_internal) |