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Diffstat (limited to 'pthreads/sem_wait.c')
| -rw-r--r-- | pthreads/sem_wait.c | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/pthreads/sem_wait.c b/pthreads/sem_wait.c new file mode 100644 index 000000000..d39d2b4b6 --- /dev/null +++ b/pthreads/sem_wait.c @@ -0,0 +1,187 @@ +/* + * ------------------------------------------------------------- + * + * Module: sem_wait.c + * + * Purpose: + * Semaphores aren't actually part of the PThreads standard. + * They are defined by the POSIX Standard: + * + * POSIX 1003.1b-1993 (POSIX.1b) + * + * ------------------------------------------------------------- + * + * -------------------------------------------------------------------------- + * + * Pthreads-win32 - POSIX Threads Library for Win32 + * Copyright(C) 1998 John E. Bossom + * Copyright(C) 1999,2005 Pthreads-win32 contributors + * + * Contact Email: rpj@callisto.canberra.edu.au + * + * The current list of contributors is contained + * in the file CONTRIBUTORS included with the source + * code distribution. The list can also be seen at the + * following World Wide Web location: + * http://sources.redhat.com/pthreads-win32/contributors.html + * + * This 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 of the License, or (at your option) any later version. + * + * This 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 this library in the file COPYING.LIB; + * if not, write to the Free Software Foundation, Inc., + * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + */ + +#include "pthread.h" +#include "semaphore.h" +#include "implement.h" + + +static void PTW32_CDECL +ptw32_sem_wait_cleanup(void * sem) +{ + sem_t s = (sem_t) sem; + + if (pthread_mutex_lock (&s->lock) == 0) + { + /* + * If sema is destroyed do nothing, otherwise:- + * If the sema is posted between us being cancelled and us locking + * the sema again above then we need to consume that post but cancel + * anyway. If we don't get the semaphore we indicate that we're no + * longer waiting. + */ + if (*((sem_t *)sem) != NULL && !(WaitForSingleObject(s->sem, 0) == WAIT_OBJECT_0)) + { + ++s->value; +#ifdef NEED_SEM + if (s->value > 0) + { + s->leftToUnblock = 0; + } +#else + /* + * Don't release the W32 sema, it doesn't need adjustment + * because it doesn't record the number of waiters. + */ +#endif /* NEED_SEM */ + } + (void) pthread_mutex_unlock (&s->lock); + } +} + +int +sem_wait (sem_t * sem) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * This function waits on a semaphore. + * + * PARAMETERS + * sem + * pointer to an instance of sem_t + * + * DESCRIPTION + * This function waits on a semaphore. If the + * semaphore value is greater than zero, it decreases + * its value by one. If the semaphore value is zero, then + * the calling thread (or process) is blocked until it can + * successfully decrease the value or until interrupted by + * a signal. + * + * RESULTS + * 0 successfully decreased semaphore, + * -1 failed, error in errno + * ERRNO + * EINVAL 'sem' is not a valid semaphore, + * ENOSYS semaphores are not supported, + * EINTR the function was interrupted by a signal, + * EDEADLK a deadlock condition was detected. + * + * ------------------------------------------------------ + */ +{ + int result = 0; + sem_t s = *sem; + + pthread_testcancel(); + + if (s == NULL) + { + result = EINVAL; + } + else + { + if ((result = pthread_mutex_lock (&s->lock)) == 0) + { + int v; + + /* See sem_destroy.c + */ + if (*sem == NULL) + { + (void) pthread_mutex_unlock (&s->lock); + errno = EINVAL; + return -1; + } + + v = --s->value; + (void) pthread_mutex_unlock (&s->lock); + + if (v < 0) + { +#ifdef _MSC_VER +#pragma inline_depth(0) +#endif + /* Must wait */ + pthread_cleanup_push(ptw32_sem_wait_cleanup, (void *) s); + result = pthreadCancelableWait (s->sem); + /* Cleanup if we're canceled or on any other error */ + pthread_cleanup_pop(result); +#ifdef _MSC_VER +#pragma inline_depth() +#endif + } +#ifdef NEED_SEM + + if (!result && pthread_mutex_lock (&s->lock) == 0) + { + if (*sem == NULL) + { + (void) pthread_mutex_unlock (&s->lock); + errno = EINVAL; + return -1; + } + + if (s->leftToUnblock > 0) + { + --s->leftToUnblock; + SetEvent(s->sem); + } + (void) pthread_mutex_unlock (&s->lock); + } + +#endif /* NEED_SEM */ + + } + + } + + if (result != 0) + { + errno = result; + return -1; + } + + return 0; + +} /* sem_wait */ |