1 /* Copyright (C) 2003-2013 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library. If not, see
16 <http://www.gnu.org/licenses/>. */
19 #include <lowlevellock.h>
22 unsigned long int __fork_generation attribute_hidden
;
25 clear_once_control (void *arg
)
27 pthread_once_t
*once_control
= (pthread_once_t
*) arg
;
30 lll_futex_wake (once_control
, INT_MAX
, LLL_PRIVATE
);
34 __pthread_once (pthread_once_t
*once_control
, void (*init_routine
) (void))
43 newval = __fork_generation | 1;
44 oldval = *once_control;
45 if ((oldval & 2) == 0)
46 *once_control = newval;
49 newval
= __fork_generation
| 1;
58 : "=&r" (oldval
), "=&r" (tmp
), "=m" (*once_control
)
59 : "r" (newval
), "m" (*once_control
));
61 /* Check if the initializer has already been done. */
62 if ((oldval
& 2) != 0)
65 /* Check if another thread already runs the initializer. */
66 if ((oldval
& 1) == 0)
69 /* Check whether the initializer execution was interrupted by a fork. */
73 /* Same generation, some other thread was faster. Wait. */
74 lll_futex_wait (once_control
, oldval
, LLL_PRIVATE
);
77 /* This thread is the first here. Do the initialization.
78 Register a cleanup handler so that in case the thread gets
79 interrupted the initialization can be restarted. */
80 pthread_cleanup_push (clear_once_control
, once_control
);
84 pthread_cleanup_pop (0);
86 /* Add one to *once_control to take the bottom 2 bits from 01 to 10. */
87 atomic_increment (once_control
);
89 /* Wake up all other threads. */
90 lll_futex_wake (once_control
, INT_MAX
, LLL_PRIVATE
);
94 weak_alias (__pthread_once
, pthread_once
)
95 hidden_def (__pthread_once
)