| 1 | /* Post a semaphore. Generic version. |
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| 2 | Copyright (C) 2005-2024 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #include <semaphore.h> |
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| 20 | #include <assert.h> |
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| 21 | |
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| 22 | #include <hurdlock.h> |
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| 23 | #include <hurd.h> |
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| 24 | |
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| 25 | #include <pt-internal.h> |
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| 26 | |
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| 27 | int |
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| 28 | __sem_post (sem_t *sem) |
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| 29 | { |
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| 30 | struct new_sem *isem = (struct new_sem *) sem; |
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| 31 | int flags = isem->pshared ? GSYNC_SHARED : 0; |
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| 32 | |
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| 33 | #if __HAVE_64B_ATOMICS |
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| 34 | uint64_t d = atomic_load_relaxed (&isem->data); |
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| 35 | |
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| 36 | do |
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| 37 | { |
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| 38 | if ((d & SEM_VALUE_MASK) == SEM_VALUE_MAX) |
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| 39 | return __hurd_fail (EOVERFLOW); |
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| 40 | } |
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| 41 | while (!atomic_compare_exchange_weak_release (&isem->data, &d, d + 1)); |
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| 42 | |
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| 43 | if ((d >> SEM_NWAITERS_SHIFT) != 0) |
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| 44 | /* Wake one waiter. */ |
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| 45 | __lll_wake (((unsigned int *) &isem->data) + SEM_VALUE_OFFSET, flags); |
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| 46 | #else |
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| 47 | unsigned int v = atomic_load_relaxed (&isem->value); |
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| 48 | |
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| 49 | do |
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| 50 | { |
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| 51 | if ((v >> SEM_VALUE_SHIFT) == SEM_VALUE_MAX) |
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| 52 | return __hurd_fail (EOVERFLOW); |
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| 53 | } |
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| 54 | while (!atomic_compare_exchange_weak_release |
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| 55 | (&isem->value, &v, v + (1 << SEM_VALUE_SHIFT))); |
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| 56 | |
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| 57 | if ((v & SEM_NWAITERS_MASK) != 0) |
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| 58 | /* Wake one waiter. */ |
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| 59 | __lll_wake (&isem->value, flags); |
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| 60 | #endif |
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| 61 | |
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| 62 | return 0; |
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| 63 | } |
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| 64 | libpthread_hidden_def (__sem_post) |
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| 65 | strong_alias (__sem_post, sem_post); |
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| 66 | |
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