/****************************************************************************
* net/uip/uip_lock.c
*
* Copyright (C) 2011-2012 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 <debug.h>
#include <nuttx/arch.h>
#include <nuttx/net/uip/uip.h>
#if defined(CONFIG_NET) && defined(CONFIG_NET_NOINTS)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define NO_HOLDER (pid_t)-1
/****************************************************************************
* Private Data
****************************************************************************/
static sem_t g_uipsem;
static pid_t g_holder = NO_HOLDER;
static unsigned int g_count = 0;
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Function: uip_takesem
*
* Description:
* Take the semaphore
*
****************************************************************************/
static void uip_takesem(void)
{
while (sem_wait(&g_uipsem) != 0)
{
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
ASSERT(errno == EINTR);
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Function: uip_lockinit
*
* Description:
* Initialize the locking facility
*
****************************************************************************/
void uip_lockinit(void)
{
sem_init(&g_uipsem, 0, 1);
}
/****************************************************************************
* Function: uip_lock
*
* Description:
* Take the lock
*
****************************************************************************/
uip_lock_t uip_lock(void)
{
pid_t me = getpid();
/* Does this thread already hold the semaphore? */
if (g_holder == me)
{
/* Yes.. just increment the reference count */
g_count++;
}
else
{
/* No.. take the semaphore (perhaps waiting) */
uip_takesem();
/* Now this thread holds the semaphore */
g_holder = me;
g_count = 1;
}
return 0;
}
/****************************************************************************
* Function: uip_unlock
*
* Description:
* Release the lock.
*
****************************************************************************/
void uip_unlock(uip_lock_t flags)
{
DEBUGASSERT(g_holder == getpid() && g_count > 0);
/* If the count would go to zero, then release the semaphore */
if (g_count == 1)
{
/* We no longer hold the semaphore */
g_holder = NO_HOLDER;
g_count = 0;
sem_post(&g_uipsem);
}
else
{
/* We still hold the semaphore. Just decrement the count */
g_count--;
}
}
/****************************************************************************
* Function: uip_lockedwait
*
* Description:
* Atomically wait for sem while temporarily releasing g_uipsem.
*
****************************************************************************/
int uip_lockedwait(sem_t *sem)
{
pid_t me = getpid();
unsigned int count;
irqstate_t flags;
int ret;
flags = irqsave(); /* No interrupts */
sched_lock(); /* No context switches */
if (g_holder == me)
{
/* Release the uIP semaphore, remembering the count */
count = g_count;
g_holder = NO_HOLDER;
g_count = 0;
sem_post(&g_uipsem);
/* Now take the semaphore */
ret = sem_wait(sem);
/* Recover the uIP semaphore at the proper count */
uip_takesem();
g_holder = me;
g_count = count;
}
else
{
ret = sem_wait(sem);
}
sched_unlock();
irqrestore(flags);
return ret;
}
#endif /* CONFIG_NET */
