posix/src/sempost.c

0001 /* SPDX-License-Identifier: BSD-2-Clause */
0002
0003 /**
0004  *  @file
0005  *
0006  *  @brief Unlock a Semaphore
0007  *  @ingroup POSIX_SEMAPHORE
0008  */
0009
0010 /*
0011  *  COPYRIGHT (c) 1989-2014.
0012  *  On-Line Applications Research Corporation (OAR).
0013  *
0014  * Redistribution and use in source and binary forms, with or without
0015  * modification, are permitted provided that the following conditions
0016  * are met:
0017  * 1. Redistributions of source code must retain the above copyright
0018  *    notice, this list of conditions and the following disclaimer.
0019  * 2. Redistributions in binary form must reproduce the above copyright
0020  *    notice, this list of conditions and the following disclaimer in the
0021  *    documentation and/or other materials provided with the distribution.
0022  *
0023  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0024  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0025  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0026  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0027  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0028  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0029  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0030  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0031  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0032  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0033  * POSSIBILITY OF SUCH DAMAGE.
0034  */
0035
0036 #ifdef HAVE_CONFIG_H
0037 #include "config.h"
0038 #endif
0039
0040 #include <rtems/posix/semaphoreimpl.h>
0041
0042 #include <limits.h>
0043
0044 int sem_post( sem_t *_sem )
0045 {
0046   Sem_Control          *sem;
0047   ISR_Level             level;
0048   Thread_queue_Context  queue_context;
0049   Thread_queue_Heads   *heads;
0050   unsigned int          count;
0051
0052   POSIX_SEMAPHORE_VALIDATE_OBJECT( _sem );
0053
0054   sem = _Sem_Get( &_sem->_Semaphore );
0055   _Thread_queue_Context_initialize( &queue_context );
0056   _Thread_queue_Context_ISR_disable( &queue_context, level );
0057   _Sem_Queue_acquire_critical( sem, &queue_context );
0058
0059   heads = sem->Queue.Queue.heads;
0060   count = sem->count;
0061
0062   if ( RTEMS_PREDICT_TRUE( heads == NULL && count < SEM_VALUE_MAX ) ) {
0063     sem->count = count + 1;
0064     _Sem_Queue_release( sem, level, &queue_context );
0065     return 0;
0066   }
0067
0068   if ( RTEMS_PREDICT_TRUE( heads != NULL ) ) {
0069     _Thread_queue_Context_set_ISR_level( &queue_context, level );
0070     _Thread_queue_Surrender_no_priority(
0071       &sem->Queue.Queue,
0072       heads,
0073       &queue_context,
0074       SEMAPHORE_TQ_OPERATIONS
0075     );
0076     return 0;
0077   }
0078
0079   _Sem_Queue_release( sem, level, &queue_context );
0080   rtems_set_errno_and_return_minus_one( EOVERFLOW );
0081 }