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- /****************************************************************************
- * fs/inode/fs_inode.c
- *
- * Copyright (C) 2007-2009, 2011-2012, 2016-2017 Gregory Nutt. All rights
- * reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * 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 NuttX 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 <nuttx/config.h>
- #include <unistd.h>
- #include <semaphore.h>
- #include <assert.h>
- #include <errno.h>
- #include <nuttx/fs/fs.h>
- #include "inode/inode.h"
- /****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
- #define NO_HOLDER ((pid_t)-1)
- /****************************************************************************
- * Private Types
- ****************************************************************************/
- /* Implements a re-entrant mutex for inode access. This must be re-entrant
- * because there can be cycles. For example, it may be necessary to destroy
- * a block driver inode on umount() after a removable block device has been
- * removed. In that case umount() holds the inode semaphore, but the block
- * driver may callback to unregister_blockdriver() after the un-mount,
- * requiring the semaphore again.
- */
- struct inode_sem_s
- {
- sem_t sem; /* The semaphore */
- pid_t holder; /* The current holder of the semaphore */
- int16_t count; /* Number of counts held */
- };
- /****************************************************************************
- * Private Data
- ****************************************************************************/
- static struct inode_sem_s g_inode_sem;
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: inode_initialize
- *
- * Description:
- * This is called from the OS initialization logic to configure the file
- * system.
- *
- ****************************************************************************/
- void inode_initialize(void)
- {
- /* Initialize the semaphore to one (to support one-at-a-time access to the
- * inode tree).
- */
- (void)nxsem_init(&g_inode_sem.sem, 0, 1);
- g_inode_sem.holder = NO_HOLDER;
- g_inode_sem.count = 0;
- /* Initialize files array (if it is used) */
- #ifdef CONFIG_HAVE_WEAKFUNCTIONS
- if (files_initialize != NULL)
- #endif
- {
- files_initialize();
- }
- }
- /****************************************************************************
- * Name: inode_semtake
- *
- * Description:
- * Get exclusive access to the in-memory inode tree (g_inode_sem).
- *
- ****************************************************************************/
- void inode_semtake(void)
- {
- pid_t me;
- /* Do we already hold the semaphore? */
- me = getpid();
- if (me == g_inode_sem.holder)
- {
- /* Yes... just increment the count */
- g_inode_sem.count++;
- DEBUGASSERT(g_inode_sem.count > 0);
- }
- /* Take the semaphore (perhaps waiting) */
- else
- {
- int ret;
- do
- {
- ret = nxsem_wait(&g_inode_sem.sem);
- /* The only case that an error should occur here is if the wait
- * was awakened by a signal.
- */
- DEBUGASSERT(ret == OK || ret == -EINTR);
- }
- while (ret == -EINTR);
- /* No we hold the semaphore */
- g_inode_sem.holder = me;
- g_inode_sem.count = 1;
- }
- }
- /****************************************************************************
- * Name: inode_semgive
- *
- * Description:
- * Relinquish exclusive access to the in-memory inode tree (g_inode_sem).
- *
- ****************************************************************************/
- void inode_semgive(void)
- {
- DEBUGASSERT(g_inode_sem.holder == getpid());
- /* Is this our last count on the semaphore? */
- if (g_inode_sem.count > 1)
- {
- /* No.. just decrement the count */
- g_inode_sem.count--;
- }
- /* Yes.. then we can really release the semaphore */
- else
- {
- g_inode_sem.holder = NO_HOLDER;
- g_inode_sem.count = 0;
- nxsem_post(&g_inode_sem.sem);
- }
- }
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