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Diffstat (limited to 'nuttx/sched/sem_close.c')
-rw-r--r-- | nuttx/sched/sem_close.c | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/nuttx/sched/sem_close.c b/nuttx/sched/sem_close.c new file mode 100644 index 000000000..3113b5156 --- /dev/null +++ b/nuttx/sched/sem_close.c @@ -0,0 +1,144 @@ +/************************************************************ + * sem_close.c + * + * Copyright (C) 2007 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name Gregory Nutt nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ************************************************************/ + +/************************************************************ + * Included Files + ************************************************************/ + +#include <sys/types.h> +#include <errno.h> +#include <semaphore.h> +#include <sched.h> +#include "os_internal.h" +#include "sem_internal.h" + +/************************************************************ + * Compilation Switches + ************************************************************/ + +/************************************************************ + * Definitions + ************************************************************/ + +/************************************************************ + * Private Type Declarations + ************************************************************/ + +/************************************************************ + * Global Variables + ************************************************************/ + +/************************************************************ + * Private Variables + ************************************************************/ + +/************************************************************ + * Private Functions + ************************************************************/ + +/************************************************************ + * Public Functions + ************************************************************/ + +/************************************************************ + * Function: sem_close + * + * Description: + * This function is called to indicate that the calling\ + * task is finished with the specified named semaphore, + * sem. The sem_close() deallocates any system resources + * allocated by the system for this named semaphore. + * + * If the semaphore has not been removed with a call to + * sem_unlink(), then sem_close() has no effect on the + * named semaphore. However, when the named semaphore has + * been fully unlinked, the semaphore will vanish when the + * last task closes it. + * + * Parameters: + * sem - semaphore descriptor + * + * Return Value: + * 0 (OK), or -1 (ERROR) if unsuccessful. + * + * Assumptions: + * - Care must be taken to avoid risking the deletion of + * a semaphore that another calling task has already + * locked. + * - sem_close must not be called for an un-named semaphore + * + ************************************************************/ + +int sem_close (sem_t *sem) +{ + nsem_t *psem; + int ret = ERROR; + + /* Verify the inputs */ + + if (sem) + { + sched_lock(); + + /* Search the list of named semaphores */ + + for (psem = (nsem_t*)g_nsems.head; + ((psem) && (sem != &psem->sem)); + psem = psem->flink); + + /* Check if we found it */ + + if (psem) + { + /* Decrement the count of sem_open connections to this semaphore */ + + if (psem->nconnect) psem->nconnect--; + + /* If the semaphore is no long connected to any processes AND the + * semaphore was previously unlinked, then deallocate it. + */ + + if (!psem->nconnect && psem->unlinked) + { + dq_rem((dq_entry_t*)psem, &g_nsems); + sched_free(psem); + } + ret = OK; + } + sched_unlock(); + } + + return ret; +} |