1 /* Lock a semaphore if it does not require blocking. Generic version.
2 Copyright (C) 2005-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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 <https://www.gnu.org/licenses/>. */
19 #include <semaphore.h>
22 #include <pt-internal.h>
25 __sem_waitfast (struct new_sem
*isem
, int definitive_result
)
27 #if __HAVE_64B_ATOMICS
28 uint64_t d
= atomic_load_relaxed (&isem
->data
);
32 if ((d
& SEM_VALUE_MASK
) == 0)
34 if (atomic_compare_exchange_weak_acquire (&isem
->data
, &d
, d
- 1))
35 /* Successful down. */
38 while (definitive_result
);
41 unsigned v
= atomic_load_relaxed (&isem
->value
);
45 if ((v
>> SEM_VALUE_SHIFT
) == 0)
47 if (atomic_compare_exchange_weak_acquire (&isem
->value
,
48 &v
, v
- (1 << SEM_VALUE_SHIFT
)))
49 /* Successful down. */
52 while (definitive_result
);