1 /* Copyright (C) 2003, 2007 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
20 #include <lowlevellock.h>
23 unsigned long int __fork_generation attribute_hidden
;
27 clear_once_control (void *arg
)
29 pthread_once_t
*once_control
= (pthread_once_t
*) arg
;
32 lll_futex_wake (once_control
, INT_MAX
, LLL_PRIVATE
);
37 __pthread_once (once_control
, init_routine
)
38 pthread_once_t
*once_control
;
39 void (*init_routine
) (void);
47 oldval = *once_control;
48 if ((oldval & 2) == 0)
50 newval = (oldval & 3) | __fork_generation | 1;
51 *once_control = newval;
53 Do this atomically. */
54 __asm
__volatile (" l %1,%0\n"
64 : "=Q" (*once_control
), "=&d" (oldval
), "=&d" (newval
)
65 : "m" (__fork_generation
), "m" (*once_control
)
67 /* Check if the initialized has already been done. */
68 if ((oldval
& 2) != 0)
70 /* Check if another thread already runs the initializer. */
71 if ((oldval
& 1) != 0)
73 /* Check whether the initializer execution was interrupted
75 if (((oldval
^ newval
) & -4) == 0)
77 /* Same generation, some other thread was faster. Wait. */
78 lll_futex_wait (once_control
, newval
, LLL_PRIVATE
);
83 /* This thread is the first here. Do the initialization.
84 Register a cleanup handler so that in case the thread gets
85 interrupted the initialization can be restarted. */
86 pthread_cleanup_push (clear_once_control
, once_control
);
90 pthread_cleanup_pop (0);
93 /* Add one to *once_control. */
94 __asm
__volatile (" l %1,%0\n"
99 : "=Q" (*once_control
), "=&d" (oldval
), "=&d" (newval
)
100 : "m" (*once_control
) : "cc" );
102 /* Wake up all other threads. */
103 lll_futex_wake (once_control
, INT_MAX
, LLL_PRIVATE
);
109 weak_alias (__pthread_once
, pthread_once
)
110 strong_alias (__pthread_once
, __pthread_once_internal
)