485 lines
14 KiB
C
485 lines
14 KiB
C
/****************************************************************************
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* mm/shm/shmget.c
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*
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* Copyright (C) 2014, 2017 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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 <sys/shm.h>
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#include <sys/ipc.h>
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#include <unistd.h>
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#include <semaphore.h>
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#include <string.h>
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#include <errno.h>
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#include <nuttx/pgalloc.h>
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#include <nuttx/mm/shm.h>
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#include "shm/shm.h"
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#ifdef CONFIG_MM_SHM
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: shm_find
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*
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* Description:
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* Find the shared memory region with matching key
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*
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* Input Parameters:
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* key - The value that uniquely identifies a shared memory region.
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*
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* Returned Value:
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* On success, an index in the range of 0 to CONFIG_ARCH_SHM_MAXREGIONS-1
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* is returned to identify the matching region; -ENOENT is returned on
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* failure.
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*
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****************************************************************************/
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static int shm_find(key_t key)
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{
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int i;
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for (i = 0; i < CONFIG_ARCH_SHM_MAXREGIONS; i++)
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{
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if (g_shminfo.si_region[i].sr_key == key)
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{
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return i;
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}
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}
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return -ENOENT;
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}
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/****************************************************************************
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* Name: shm_reserve
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*
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* Description:
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* Allocate an unused shared memory region. That is one with a key of -1
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* On success, an index in the range of 0 to CONFIG_ARCH_SHM_MAXREGIONS-1
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* is returned to identify the matching region; -ENOSPC is returned on
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* failure.
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*
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****************************************************************************/
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static int shm_reserve(key_t key, int shmflg)
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{
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FAR struct shm_region_s *region;
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int i;
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for (i = 0; i < CONFIG_ARCH_SHM_MAXREGIONS; i++)
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{
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/* Is this region in use? */
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region = &g_shminfo.si_region[i];
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if (region->sr_flags == SRFLAG_AVAILABLE)
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{
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/* No... reserve it for the caller now */
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memset(region, 0, sizeof(struct shm_region_s));
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region->sr_key = key;
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region->sr_flags = SRFLAG_INUSE;
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nxsem_init(®ion->sr_sem, 0, 1);
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/* Set the low-order nine bits of shm_perm.mode to the low-order
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* nine bits of shmflg.
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*/
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region->sr_ds.shm_perm.mode = shmflg & IPC_MODE;
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/* The value of shm_segsz is left equal to zero for now because no
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* memory has yet been allocated.
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*
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* The values of shm_lpid, shm_nattch, shm_atime, and shm_dtime are
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* set equal to 0.
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*/
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/* The value of shm_ctime is set equal to the current time. */
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region->sr_ds.shm_ctime = time(NULL);
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return i;
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}
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}
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return -ENOSPC;
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}
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/****************************************************************************
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* Name: shm_extend
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*
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* Description:
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* Extend the size of a memory regions by allocating physical pages as
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* necessary
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*
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* Input Parameters:
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* shmid - The index of the region of interest in the shared memory region
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* table.
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* size - The new size of the region.
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*
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* Returned Value:
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* Zero is returned on success; -ENOMEM is returned on failure.
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* (Should a different error be returned if the region is just too big?)
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*
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****************************************************************************/
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static int shm_extend(int shmid, size_t size)
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{
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FAR struct shm_region_s *region = &g_shminfo.si_region[shmid];
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unsigned int pgalloc;
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unsigned int pgneeded;
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/* This is the number of pages that are needed to satisfy the allocation */
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pgneeded = MM_PGALIGNUP(size);
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/* This is the number of pages that have already been allocated */
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pgalloc = MM_PGALIGNUP(region->sr_ds.shm_segsz);
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/* Loop until all pages have been allocated (or something bad happens) */
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while (pgalloc < pgneeded && pgalloc < CONFIG_ARCH_SHM_NPAGES)
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{
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/* Allocate one more physical page */
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region->sr_pages[pgalloc] = mm_pgalloc(1);
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if (region->sr_pages[pgalloc] == 0)
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{
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shmerr("ERROR: mm_pgalloc(1) failed\n");
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break;
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}
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/* Increment the number of pages successully allocated */
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pgalloc++;
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}
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/* We get here (1) because all of the pages were successfully, (2) because
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* mm_pgalloc() failed, or (3) because any additional pages allocated
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* would exceed CONFIG_ARCH_SHM_NPAGES.
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*/
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if (pgalloc < pgneeded)
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{
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/* Set the amount memory available which will be less than the
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* requested size.
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*/
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region->sr_ds.shm_segsz = pgalloc << MM_PGSHIFT;
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return -ENOMEM;
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}
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/* Set the new region size and return success */
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region->sr_ds.shm_segsz = size;
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return OK;
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}
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/****************************************************************************
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* Name: shm_create
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*
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* Description:
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* Create the shared memory region.
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*
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* Input Parameters:
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* key - The key that is used to access the unique shared memory
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* identifier.
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* size - The shared memory region that is created will be at least
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* this size in bytes.
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* shmflgs - See IPC_* definitions in sys/ipc.h. Only the values
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* IPC_PRIVATE or IPC_CREAT are supported.
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*
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* Returned Value:
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* Zero is returned on success; A negated errno value is returned on
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* failure.
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*
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****************************************************************************/
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static int shm_create(key_t key, size_t size, int shmflg)
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{
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FAR struct shm_region_s *region;
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int shmid;
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int ret;
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/* Reserve the shared memory region */
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ret = shm_reserve(key, shmflg);
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if (ret < 0)
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{
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shmerr("ERROR: shm_reserve failed: %d\n", ret);
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return ret;
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}
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/* Save the shared memory ID */
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shmid = ret;
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/* Then allocate the physical memory (by extending it from the initial
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* size of zero).
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*/
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ret = shm_reserve(shmid, size);
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if (ret < 0)
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{
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/* Free any partial allocations and unreserve the region */
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shm_destroy(shmid);
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return ret;
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}
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/* Save the process ID of the creator */
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region = &g_shminfo.si_region[shmid];
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region->sr_ds.shm_cpid = getpid();
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/* Return the shared memory ID */
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return shmid;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: shmget
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*
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* Description:
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* The shmget() function will return the shared memory identifier
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* associated with key.
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*
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* A shared memory identifier, associated data structure, and shared
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* memory segment of at least size bytes is created for key if one of the
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* following is true:
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*
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* - The argument key is equal to IPC_PRIVATE.
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* - The argument key does not already have a shared memory identifier
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* associated with it and (shmflg & IPC_CREAT) is non-zero.
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*
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* Upon creation, the data structure associated with the new shared memory
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* identifier will be initialized as follows:
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*
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* - The low-order nine bits of shm_perm.mode are set equal to the low-
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* order nine bits of shmflg.
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* - The value of shm_segsz is set equal to the value of size.
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* - The values of shm_lpid, shm_nattch, shm_atime, and shm_dtime are
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* set equal to 0.
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* - The value of shm_ctime is set equal to the current time.
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*
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* When the shared memory segment is created, it will be initialized with
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* all zero values.
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*
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* Input Parameters:
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* key - The key that is used to access the unique shared memory
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* identifier.
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* size - The shared memory region that is created will be at least
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* this size in bytes.
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* shmflgs - See IPC_* definitions in sys/ipc.h. Only the values
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* IPC_PRIVATE or IPC_CREAT are supported.
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*
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* Returned Value:
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* Upon successful completion, shmget() will return a non-negative
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* integer, namely a shared memory identifier; otherwise, it will return
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* -1 and set errno to indicate the error.
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*
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* - EACCES
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* A shared memory identifier exists for key but operation permission
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* as specified by the low-order nine bits of shmflg would not be
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* granted.
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* - EEXIST
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* A shared memory identifier exists for the argument key but
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* (shmflg & IPC_CREAT) && (shmflg & IPC_EXCL) are non-zero.
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* - EINVAL
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* A shared memory segment is to be created and the value of size is
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* less than the system-imposed minimum or greater than the system-
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* imposed maximum.
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* - EINVAL
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* No shared memory segment is to be created and a shared memory
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* segment exists for key but the size of the segment associated with
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* it is less than size and size is not 0.
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* - ENOENT
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* A shared memory identifier does not exist for the argument key and
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* (shmflg & IPC_CREAT) is 0.
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* - ENOMEM
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* A shared memory identifier and associated shared memory segment
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* will be created, but the amount of available physical memory is
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* not sufficient to fill the request.
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* - ENOSPC
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* A shared memory identifier is to be created, but the system-imposed
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* limit on the maximum number of allowed shared memory identifiers
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* system-wide would be exceeded.
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*
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* POSIX Deviations:
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* - The values of shm_perm.cuid, shm_perm.uid, shm_perm.cgid, and
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* shm_perm.gid should be set equal to the effective user ID and
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* effective group ID, respectively, of the calling process.
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* The NuttX ipc_perm structure, however, does not support these
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* fields because user and group IDs are not yet supported by NuttX.
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*
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****************************************************************************/
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int shmget(key_t key, size_t size, int shmflg)
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{
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FAR struct shm_region_s *region;
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int shmid = -1;
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int ret;
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/* Check for the special case where the caller doesn't really want shared
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* memory (they why do they bother to call us?)
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*/
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if (key == IPC_PRIVATE)
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{
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/* Not yet implemented */
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ret = -ENOSYS;
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goto errout;
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}
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/* Get exclusive access to the global list of shared memory regions */
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ret = nxsem_wait(&g_shminfo.si_sem);
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if (ret < 0)
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{
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goto errout;
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}
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/* Find the requested memory region */
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ret = shm_find(key);
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if (ret < 0)
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{
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/* The memory region does not exist.. create it if IPC_CREAT is
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* included in the shmflags.
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*/
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if ((shmflg & IPC_CREAT) != 0)
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{
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/* Create the memory region */
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ret = shm_create(key, size, shmflg);
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if (ret < 0)
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{
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shmerr("ERROR: shm_create failed: %d\n", ret);
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goto errout_with_semaphore;
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}
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/* Return the shared memory ID */
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shmid = ret;
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}
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else
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{
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/* Fail with ENOENT */
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goto errout_with_semaphore;
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}
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}
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/* The region exists */
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else
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{
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/* Remember the shared memory ID */
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shmid = ret;
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/* Is the region big enough for the request? */
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region = &g_shminfo.si_region[shmid];
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if (region->sr_ds.shm_segsz < size)
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{
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/* We we asked to create the region? If so we can just
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* extend it.
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*
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* REVISIT: We should check the mode bits of the regions
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* first
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*/
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if ((shmflg & IPC_CREAT) != 0)
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{
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/* Extend the region */
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ret = shm_extend(shmid, size);
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if (ret < 0)
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{
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shmerr("ERROR: shm_create failed: %d\n", ret);
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goto errout_with_semaphore;
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}
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}
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else
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{
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/* Fail with EINVAL */
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ret = -EINVAL;
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goto errout_with_semaphore;
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}
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}
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/* The region is already big enough or else we successfully
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* extended the size of the region. If the region was previously
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* deleted, but waiting for processes to detach from the region,
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* then it is no longer deleted.
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*/
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region->sr_flags = SRFLAG_INUSE;
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}
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/* Release our lock on the shared memory region list */
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nxsem_post(&g_shminfo.si_sem);
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return shmid;
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errout_with_semaphore:
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nxsem_post(&g_shminfo.si_sem);
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errout:
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set_errno(-ret);
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return ERROR;
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}
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#endif /* CONFIG_MM_SHM */
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