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git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@3724 7fd9a85b-ad96-42d3-883c-3090e2eb8679
250 lines
6.9 KiB
C
250 lines
6.9 KiB
C
/****************************************************************************
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* mm/mm_sem.c
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*
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* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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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 "mm_environment.h"
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#include <unistd.h>
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#include <semaphore.h>
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#include <errno.h>
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#include <assert.h>
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#include "mm_internal.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Define the following to enable semaphore state monitoring */
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//#define MONITOR_MM_SEMAPHORE 1
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#ifdef MONITOR_MM_SEMAPHORE
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# ifdef CONFIG_DEBUG
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# include <debug.h>
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# define msemdbg dbg
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# else
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# define msemdbg printf
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# endif
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#else
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# ifdef CONFIG_CPP_HAVE_VARARGS
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# define msemdbg(x...)
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# else
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# define msemdbg (void)
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# endif
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#endif
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/* Mutually exclusive access to this data set is enforced with
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* the following (un-named) semaphore. */
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static sem_t g_mm_semaphore;
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static pid_t g_holder;
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static int g_counts_held;
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mm_seminitialize
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*
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* Description:
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* Initialize the MM mutex
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*
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****************************************************************************/
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void mm_seminitialize(void)
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{
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/* Initialize the MM semaphore to one (to support one-at-
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* a-time access to private data sets.
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*/
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(void)sem_init(&g_mm_semaphore, 0, 1);
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g_holder = -1;
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g_counts_held = 0;
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}
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/****************************************************************************
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* Name: mm_trysemaphore
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*
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* Description:
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* Try to take the MM mutex. This is called only from the
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* OS in certain conditions when it is necessary to have
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* exclusive access to the memory manager but it is
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* impossible to wait on a semaphore (e.g., the idle process
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* when it performs its background memory cleanup).
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*
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****************************************************************************/
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#ifndef MM_TEST
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int mm_trysemaphore(void)
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{
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pid_t my_pid = getpid();
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/* Do I already have the semaphore? */
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if (g_holder == my_pid)
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{
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/* Yes, just increment the number of references that I have */
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g_counts_held++;
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return OK;
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}
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else
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{
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/* Try to tak the semaphore (perhaps waiting) */
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if (sem_trywait(&g_mm_semaphore) != 0)
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{
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return ERROR;
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}
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/* We have it. Claim the stak and return */
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g_holder = my_pid;
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g_counts_held = 1;
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return OK;
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}
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}
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#endif
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/****************************************************************************
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* Name: mm_takesemaphore
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*
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* Description:
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* Take the MM mutex. This is the normal action before all
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* memory management actions.
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*
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****************************************************************************/
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void mm_takesemaphore(void)
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{
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pid_t my_pid = getpid();
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/* Do I already have the semaphore? */
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if (g_holder == my_pid)
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{
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/* Yes, just increment the number of references that I have */
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g_counts_held++;
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}
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else
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{
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/* Take the semaphore (perhaps waiting) */
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msemdbg("PID=%d taking\n", my_pid);
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while (sem_wait(&g_mm_semaphore) != 0)
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{
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/* The only case that an error should occur here is if
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* the wait was awakened by a signal.
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*/
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ASSERT(mm_errno == EINTR);
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}
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/* We have it. Claim the stake and return */
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g_holder = my_pid;
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g_counts_held = 1;
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}
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msemdbg("Holder=%d count=%d\n",
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g_holder, g_counts_held);
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}
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/****************************************************************************
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* Name: mm_givesemaphore
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*
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* Description:
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* Release the MM mutex when it is not longer needed.
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*
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****************************************************************************/
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void mm_givesemaphore(void)
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{
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#ifdef CONFIG_DEBUG
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pid_t my_pid = getpid();
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#endif
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/* I better be holding at least one reference to the semaphore */
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DEBUGASSERT(g_holder == my_pid);
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/* Do I hold multiple references to the semphore */
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if (g_counts_held > 1)
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{
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/* Yes, just release one count and return */
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g_counts_held--;
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msemdbg("Holder=%d count=%d\n",
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g_holder, g_counts_held);
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}
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else
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{
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/* Nope, this is the last reference I have */
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msemdbg("PID=%d giving\n", my_pid);
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g_holder = -1;
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g_counts_held = 0;
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ASSERT(sem_post(&g_mm_semaphore) == 0);
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}
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}
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/****************************************************************************
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* Name: mm_getsemaphore
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*
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* Description:
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* Return the current value of the MM semaphore (for test
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* purposes only)
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*
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****************************************************************************/
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#ifdef MM_TEST
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int mm_getsemaphore(void)
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{
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int sval;
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sem_getvalue(&g_mm_semaphore, &sval);
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return sval;
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}
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#endif
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