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/****************************************************************************
* mm/shm/shmdt.c
*
* Copyright (C) 2014 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 <sys/shm.h>
#include <errno.h>
#include <nuttx/arch.h>
#include <nuttx/sched.h>
#include <nuttx/shm.h>
#include "shm/shm.h"
#ifdef CONFIG_MM_SHM
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: shmdt
*
* Description:
* The shmdt() 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
*
* Returned Value:
* Upon successful completion, shmdt() 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()
& 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(FAR const void *shmaddr)
{
FAR struct shm_region_s *region;
FAR struct task_group_s *group;
FAR struct tcb_s *tcb;
unsigned int npages;
int shmid;
int ret;
/* Get the TCB and group containing our virtual memory allocator */
tcb = sched_self();
DEBUGASSERT(tcb && tcb->group);
group = tcb->group;
DEBUGASSERT(group->tg_shm.gs_handle != NULL);
/* Perform the reverse lookup to get the shmid corresponding to this
* shmaddr.
*/
for (shmid = 0;
shmid < CONFIG_ARCH_SHM_MAXREGIONS &&
group->tg_shm.gs_vaddr[shmid] != (uintptr_t)shmaddr;
shmid++);
if (shmid >= CONFIG_ARCH_SHM_MAXREGIONS)
{
shmdbg("No region matching this virtual address: %p\n", shmaddr);
ret = -EINVAL;
goto errout_with_errno;
}
/* 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 = sem_wait(®ion->sr_sem);
if (ret < 0)
{
shmdbg("sem_wait failed: %d\n", ret);
goto errout;
}
/* Free the virtual address space */
gran_free(group->tg_shm.gs_handle, (FAR void *)shmaddr,
region->sr_ds.shm_segsz);
/* Convert the region size to pages */
npages = MM_PGALIGNUP(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)
{
shmdbg("up_shmdt() failed\n");
}
/* Indicate that there is no longer any mapping for this region. */
group->tg_shm.gs_vaddr[shmid] = 0;
/* 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 the last operation */
region->sr_ds.shm_lpid = tcb->pid;
/* Save the time of the last shmdt() */
region->sr_ds.shm_dtime = time(NULL);
/* Release our lock on the entry */
sem_post(®ion->sr_sem);
return OK;
errout_with_errno:
set_errno(-ret);
errout:
return ERROR;
}
#endif /* CONFIG_MM_SHM */
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