1 | /* Lock a semaphore if it does not require blocking. Generic version. |
2 | Copyright (C) 2005-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
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. |
9 | |
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. |
14 | |
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/>. */ |
18 | |
19 | #include <semaphore.h> |
20 | #include <errno.h> |
21 | |
22 | #include <pt-internal.h> |
23 | |
24 | int |
25 | __sem_waitfast (struct new_sem *isem, int definitive_result) |
26 | { |
27 | #if __HAVE_64B_ATOMICS |
28 | uint64_t d = atomic_load_relaxed (&isem->data); |
29 | |
30 | do |
31 | { |
32 | if ((d & SEM_VALUE_MASK) == 0) |
33 | break; |
34 | if (atomic_compare_exchange_weak_acquire (&isem->data, &d, d - 1)) |
35 | /* Successful down. */ |
36 | return 0; |
37 | } |
38 | while (definitive_result); |
39 | return -1; |
40 | #else |
41 | unsigned v = atomic_load_relaxed (&isem->value); |
42 | |
43 | do |
44 | { |
45 | if ((v >> SEM_VALUE_SHIFT) == 0) |
46 | break; |
47 | if (atomic_compare_exchange_weak_acquire (&isem->value, |
48 | &v, v - (1 << SEM_VALUE_SHIFT))) |
49 | /* Successful down. */ |
50 | return 0; |
51 | } |
52 | while (definitive_result); |
53 | return -1; |
54 | #endif |
55 | } |
56 | |