a4d6af8343
Resolution of Issue 619 will require multiple steps, this part of the first step in that resolution: Every call to nxsem_wait_uninterruptible() must handle the return value from nxsem_wait_uninterruptible properly. This commit is only for those files under fs/inode. Utility functions under fs/incode were modified so the changes do extend to other fs/ sub-directories as well.
255 lines
7.1 KiB
C
255 lines
7.1 KiB
C
/****************************************************************************
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* fs/semaphore/sem_open.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <string.h>
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#include <sched.h>
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#include <errno.h>
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#include <nuttx/kmalloc.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/fs/fs.h>
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#include "inode/inode.h"
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#include "semaphore/semaphore.h"
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#ifdef CONFIG_FS_NAMED_SEMAPHORES
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sem_open
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*
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* Description:
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* This function establishes a connection between named semaphores and a
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* task. Following a call to sem_open() with the semaphore name, the task
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* may reference the semaphore associated with name using the address
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* returned by this call. The semaphore may be used in subsequent calls
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* to sem_wait(), sem_trywait(), and sem_post(). The semaphore remains
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* usable until the semaphore is closed by a successful call to
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* sem_close().
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*
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* If a task makes multiple calls to sem_open() with the same name, then
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* the same semaphore address is returned (provided there have been no
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* calls to sem_unlink()).
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*
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* Input Parameters:
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* name - Semaphore name
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* oflags - Semaphore creation options. This may either or both of the
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* following bit settings.
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* oflags = 0: Connect to the semaphore only if it already exists.
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* oflags = O_CREAT: Connect to the semaphore if it exists, otherwise
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* create the semaphore.
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* oflags = O_CREAT|O_EXCL: Create a new semaphore
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* unless one of this name already exists.
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* Optional parameters. When the O_CREAT flag is specified, two optional
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* parameters are expected:
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* 1. mode_t mode (ignored), and
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* 2. unsigned int value. This initial value of the semaphore. Valid
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* initial values of the semaphore must be less than or equal to
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* SEM_VALUE_MAX.
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*
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* Returned Value:
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* A pointer to sem_t or SEM_FAILED if unsuccessful.
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*
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* Assumptions:
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*
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****************************************************************************/
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FAR sem_t *sem_open (FAR const char *name, int oflags, ...)
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{
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FAR struct inode *inode;
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FAR struct nsem_inode_s *nsem;
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FAR sem_t *sem = (FAR sem_t *)ERROR;
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struct inode_search_s desc;
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char fullpath[MAX_SEMPATH];
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mode_t mode;
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unsigned value;
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int errcode;
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int ret;
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/* Make sure that a non-NULL name is supplied */
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DEBUGASSERT(name != NULL);
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/* The POSIX specification requires that the "check for the existence
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* of a semaphore and the creation of the semaphore if it does not
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* exist shall be atomic with respect to other processes executing
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* sem_open()..." A simple sched_lock() should be sufficient to meet
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* this requirement.
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*/
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sched_lock();
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/* Get the full path to the semaphore */
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snprintf(fullpath, MAX_SEMPATH, CONFIG_FS_NAMED_SEMPATH "/%s", name);
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/* Get the inode for this semaphore. This should succeed if the
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* semaphore has already been created. In this case, inode_find()
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* will have incremented the reference count on the inode.
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*/
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SETUP_SEARCH(&desc, fullpath, false);
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ret = inode_find(&desc);
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if (ret >= 0)
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{
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/* Something exists at this path. Get the search results */
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inode = desc.node;
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DEBUGASSERT(inode != NULL);
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/* Verify that the inode is a semaphore */
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if (!INODE_IS_NAMEDSEM(inode))
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{
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errcode = ENXIO;
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goto errout_with_inode;
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}
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/* It exists and is a semaphore. Check if the caller wanted to
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* create a new semaphore with this name.
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*/
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if ((oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
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{
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errcode = EEXIST;
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goto errout_with_inode;
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}
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/* Return a reference to the semaphore, retaining the reference
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* count on the inode.
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*/
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sem = &inode->u.i_nsem->ns_sem;
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}
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else
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{
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va_list ap;
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/* The semaphore does not exists. Were we asked to create it? */
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if ((oflags & O_CREAT) == 0)
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{
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/* The semaphore does not exist and O_CREAT is not set */
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errcode = ENOENT;
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goto errout_with_lock;
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}
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/* Create the semaphore. First we have to extract the additional
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* parameters from the variable argument list.
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* REVISIT: Mode parameter is not currently used.
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*/
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va_start(ap, oflags);
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mode = va_arg(ap, mode_t);
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value = va_arg(ap, unsigned);
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va_end(ap);
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UNUSED(mode);
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/* Check the semaphore value */
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if (value > SEM_VALUE_MAX)
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{
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errcode = EINVAL;
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goto errout_with_lock;
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}
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/* Create an inode in the pseudo-filesystem at this path. The new
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* inode will be created with a reference count of zero.
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*/
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ret = inode_semtake();
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if (ret < 0)
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{
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errcode = -ret;
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goto errout_with_lock;
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}
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ret = inode_reserve(fullpath, &inode);
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inode_semgive();
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if (ret < 0)
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{
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errcode = -ret;
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goto errout_with_lock;
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}
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/* Allocate the semaphore structure (using the appropriate allocator
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* for the group)
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*/
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nsem = group_malloc(NULL, sizeof(struct nsem_inode_s));
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if (!nsem)
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{
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errcode = ENOMEM;
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goto errout_with_inode;
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}
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/* Link to the inode */
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inode->u.i_nsem = nsem;
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nsem->ns_inode = inode;
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/* Initialize the inode */
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INODE_SET_NAMEDSEM(inode);
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inode->i_crefs = 1;
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/* Initialize the semaphore */
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nxsem_init(&nsem->ns_sem, 0, value);
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/* Return a reference to the semaphore */
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sem = &nsem->ns_sem;
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}
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RELEASE_SEARCH(&desc);
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sched_unlock();
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return sem;
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errout_with_inode:
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inode_release(inode);
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errout_with_lock:
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RELEASE_SEARCH(&desc);
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set_errno(errcode);
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sched_unlock();
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return SEM_FAILED;
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}
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#endif /* CONFIG_FS_NAMED_SEMAPHORES */
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