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Diffstat (limited to 'sysdeps/htl/sem-waitfast.c')
-rw-r--r-- | sysdeps/htl/sem-waitfast.c | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/sysdeps/htl/sem-waitfast.c b/sysdeps/htl/sem-waitfast.c new file mode 100644 index 0000000000..7ece73da26 --- /dev/null +++ b/sysdeps/htl/sem-waitfast.c @@ -0,0 +1,55 @@ +/* Lock a semaphore if it does not require blocking. Generic version. + Copyright (C) 2005-2020 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <semaphore.h> +#include <errno.h> + +#include <pt-internal.h> + +int +__sem_waitfast (struct new_sem *isem, int definitive_result) +{ +#if __HAVE_64B_ATOMICS + uint64_t d = atomic_load_relaxed (&isem->data); + + do + { + if ((d & SEM_VALUE_MASK) == 0) + break; + if (atomic_compare_exchange_weak_acquire (&isem->data, &d, d - 1)) + /* Successful down. */ + return 0; + } + while (definitive_result); + return -1; +#else + unsigned v = atomic_load_relaxed (&isem->value); + + do + { + if ((v >> SEM_VALUE_SHIFT) == 0) + break; + if (atomic_compare_exchange_weak_acquire (&isem->value, + &v, v - (1 << SEM_VALUE_SHIFT))) + /* Successful down. */ + return 0; + } + while (definitive_result); + return -1; +#endif +} |