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/* sem_wait -- wait on a semaphore. Generic futex-using version. Copyright (C) 2003, 2007 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003. 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 <http://www.gnu.org/licenses/>. */ #include <errno.h> #include <sysdep.h> #include <lowlevellock.h> #include <internaltypes.h> #include <semaphore.h> #include <pthreadP.h> void attribute_hidden __sem_wait_cleanup (void *arg) { struct new_sem *isem = (struct new_sem *) arg; atomic_decrement (&isem->nwaiters); } int sem_wait (sem_t *sem) { struct new_sem *isem = (struct new_sem *) sem; int err; if (atomic_decrement_if_positive (&isem->value) > 0) return 0; atomic_increment (&isem->nwaiters); pthread_cleanup_push (__sem_wait_cleanup, isem); while (1) { /* Enable asynchronous cancellation. Required by the standard. */ int oldtype = __pthread_enable_asynccancel (); err = lll_futex_wait (&isem->value, 0, isem->private ^ FUTEX_PRIVATE_FLAG); /* Disable asynchronous cancellation. */ __pthread_disable_asynccancel (oldtype); if (err != 0 && err != -EWOULDBLOCK) { __set_errno (-err); err = -1; break; } if (atomic_decrement_if_positive (&isem->value) > 0) { err = 0; break; } } pthread_cleanup_pop (0); atomic_decrement (&isem->nwaiters); return err; } |