nuttx/mm/shm/shmdt.c

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/****************************************************************************
* mm/shm/shmdt.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/shm.h>
#include <assert.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/arch.h>
#include <nuttx/sched.h>
#include <nuttx/mm/shm.h>
#include <nuttx/pgalloc.h>
#include <nuttx/mm/map.h>
#include "shm/shm.h"
#ifdef CONFIG_MM_SHM
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: shmdt_priv
*
* Description:
* The shmdt_priv() function detaches the shared memory segment located at
* the address specified by shmaddr from the address space of the calling
* process.
*
* Input Parameters:
* shmid - Shared memory identifier
* group - Current task_group, NULL during process exit
*
* Returned Value:
* Upon successful completion, shmdt_priv() will decrement the value of
* shm_nattch in the data structure associated with the shared memory ID
* of the attached shared memory segment and return 0.
*
* Otherwise, the shared memory segment will not be detached, shmdt_priv()
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* will return -1, and errno will be set to indicate the error.
*
* - EINVAL
* The value of shmaddr is not the data segment start address of a
* shared memory segment.
*
****************************************************************************/
int shmdt_priv(FAR struct task_group_s *group, FAR const void *shmaddr,
int shmid)
{
FAR struct shm_region_s *region;
pid_t pid;
unsigned int npages;
int ret;
/* Get the region associated with the shmid */
region = &g_shminfo.si_region[shmid];
DEBUGASSERT((region->sr_flags & SRFLAG_INUSE) != 0);
/* Get exclusive access to the region data structure */
ret = nxmutex_lock(&region->sr_lock);
if (ret < 0)
{
shmerr("ERROR: nxsem_wait failed: %d\n", ret);
goto errout_with_errno;
}
if (!group)
{
pid = 0;
goto on_process_exit;
}
else
{
pid = group->tg_pid;
}
/* Free the virtual address space */
shm_free(group, (FAR void *)shmaddr, region->sr_ds.shm_segsz);
/* Convert the region size to pages */
npages = MM_NPAGES(region->sr_ds.shm_segsz);
/* Detach, i.e, unmap, on shared memory region from a user virtual
* address.
*/
ret = up_shmdt((uintptr_t)shmaddr, npages);
if (ret < 0)
{
shmerr("ERROR: up_shmdt() failed\n");
}
on_process_exit:
/* Decrement the count of processes attached to this region.
* If the count decrements to zero and there is a pending unlink,
* then destroy the shared memory region now and stop any further
* operations on it.
*/
DEBUGASSERT(region->sr_ds.shm_nattch > 0);
if (region->sr_ds.shm_nattch <= 1)
{
region->sr_ds.shm_nattch = 0;
if ((region->sr_flags & SRFLAG_UNLINKED) != 0)
{
shm_destroy(shmid);
return OK;
}
}
else
{
/* Just decrement the number of processes attached to the shared
* memory region.
*/
region->sr_ds.shm_nattch--;
}
/* Save the process ID of the last operation */
region->sr_ds.shm_lpid = pid;
/* Save the time of the last shmdt() */
region->sr_ds.shm_dtime = time(NULL);
/* Release our lock on the entry */
nxmutex_unlock(&region->sr_lock);
return OK;
errout_with_errno:
set_errno(-ret);
return ERROR;
}
int shmdt(FAR const void *shmaddr)
{
FAR struct tcb_s *tcb;
FAR struct mm_map_entry_s *entry;
FAR struct task_group_s *group;
int shmid;
int ret;
/* Get the TCB and group containing our virtual memory allocator */
tcb = nxsched_self();
DEBUGASSERT(tcb && tcb->group);
group = tcb->group;
/* Get exclusive access to process' mm_map */
ret = mm_map_lock();
if (ret == OK)
{
/* Perform the reverse lookup to get the shmid corresponding to this
* shmaddr. The mapping is matched with just shmaddr == map->vaddr.
*/
entry = mm_map_find(shmaddr, 1);
if (!entry || entry->vaddr != shmaddr)
{
ret = -EINVAL;
shmerr("ERROR: No region matching this virtual address: %p\n",
shmaddr);
mm_map_unlock();
return -EINVAL;
}
shmid = entry->priv.i;
/* Indicate that there is no longer any mapping for this region. */
if (mm_map_remove(get_group_mm(group), entry) < 0)
{
shmerr("ERROR: mm_map_remove() failed\n");
}
mm_map_unlock();
ret = shmdt_priv(tcb->group, shmaddr, shmid);
}
return ret;
}
#endif /* CONFIG_MM_SHM */