407 lines
11 KiB
C
407 lines
11 KiB
C
/****************************************************************************
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* net/utils/net_lock.c
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*
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* Copyright (C) 2011-2012, 2014-2018 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 <unistd.h>
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#include <semaphore.h>
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#include <assert.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/mm/iob.h>
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#include <nuttx/net/net.h>
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#include "utils/utils.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define NO_HOLDER (pid_t)-1
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static sem_t g_netlock;
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static pid_t g_holder = NO_HOLDER;
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static unsigned int g_count = 0;
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: _net_takesem
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*
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* Description:
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* Take the semaphore, waiting indefinitely.
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* REVISIT: Should this return if -EINTR?
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*
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****************************************************************************/
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static void _net_takesem(void)
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{
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int ret;
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do
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{
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/* Take the semaphore (perhaps waiting) */
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ret = nxsem_wait(&g_netlock);
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/* The only case that an error should occur here is if the wait was
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* awakened by a signal.
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*/
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DEBUGASSERT(ret == OK || ret == -EINTR);
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}
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while (ret == -EINTR);
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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: net_lockinitialize
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*
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* Description:
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* Initialize the locking facility
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*
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****************************************************************************/
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void net_lockinitialize(void)
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{
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nxsem_init(&g_netlock, 0, 1);
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}
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/****************************************************************************
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* Name: net_lock
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*
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* Description:
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* Take the network lock
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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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* None
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*
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****************************************************************************/
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void net_lock(void)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags = enter_critical_section();
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#endif
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pid_t me = getpid();
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/* Does this thread already hold the semaphore? */
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if (g_holder == me)
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{
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/* Yes.. just increment the reference count */
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g_count++;
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}
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else
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{
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/* No.. take the semaphore (perhaps waiting) */
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_net_takesem();
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/* Now this thread holds the semaphore */
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g_holder = me;
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g_count = 1;
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}
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#ifdef CONFIG_SMP
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leave_critical_section(flags);
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#endif
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}
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/****************************************************************************
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* Name: net_unlock
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*
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* Description:
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* Release the network lock.
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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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* None
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*
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****************************************************************************/
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void net_unlock(void)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags = enter_critical_section();
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#endif
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DEBUGASSERT(g_holder == getpid() && g_count > 0);
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/* If the count would go to zero, then release the semaphore */
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if (g_count == 1)
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{
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/* We no longer hold the semaphore */
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g_holder = NO_HOLDER;
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g_count = 0;
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nxsem_post(&g_netlock);
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}
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else
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{
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/* We still hold the semaphore. Just decrement the count */
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g_count--;
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}
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#ifdef CONFIG_SMP
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leave_critical_section(flags);
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#endif
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}
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/****************************************************************************
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* Name: net_breaklock
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*
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* Description:
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* Break the lock, return information needed to restore re-entrant lock
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* state.
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*
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****************************************************************************/
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int net_breaklock(FAR unsigned int *count)
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{
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irqstate_t flags;
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pid_t me = getpid();
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int ret = -EPERM;
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DEBUGASSERT(count != NULL);
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flags = spin_lock_irqsave(); /* No interrupts */
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if (g_holder == me)
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{
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/* Return the lock setting */
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*count = g_count;
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/* Release the network lock */
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g_holder = NO_HOLDER;
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g_count = 0;
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(void)nxsem_post(&g_netlock);
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ret = OK;
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}
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spin_unlock_irqrestore(flags);
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return ret;
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}
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/****************************************************************************
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* Name: net_breaklock
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*
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* Description:
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* Restore the locked state
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*
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****************************************************************************/
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void net_restorelock(unsigned int count)
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{
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pid_t me = getpid();
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DEBUGASSERT(g_holder != me);
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/* Recover the network lock at the proper count */
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_net_takesem();
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g_holder = me;
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g_count = count;
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}
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/****************************************************************************
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* Name: net_timedwait
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*
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* Description:
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* Atomically wait for sem (or a timeout( while temporarily releasing
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* the lock on the network.
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*
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* Caution should be utilized. Because the network lock is relinquished
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* during the wait, there could changes in the network state that occur
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* before the lock is recovered. Your design should account for this
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* possibility.
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*
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* Input Parameters:
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* sem - A reference to the semaphore to be taken.
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* abstime - The absolute time to wait until a timeout is declared.
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*
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* Returned Value:
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* Zero (OK) is returned on success; a negated errno value is returned on
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* any failure.
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*
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****************************************************************************/
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int net_timedwait(sem_t *sem, FAR const struct timespec *abstime)
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{
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unsigned int count;
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irqstate_t flags;
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int blresult;
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int ret;
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flags = enter_critical_section(); /* No interrupts */
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sched_lock(); /* No context switches */
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/* Release the network lock, remembering my count. net_breaklock will
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* return a negated value if the caller does not hold the network lock.
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*/
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blresult = net_breaklock(&count);
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/* Now take the semaphore, waiting if so requested. */
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if (abstime != NULL)
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{
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/* Wait until we get the lock or until the timeout expires */
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ret = nxsem_timedwait(sem, abstime);
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}
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else
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{
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/* Wait as long as necessary to get the lock */
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ret = nxsem_wait(sem);
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}
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/* Recover the network lock at the proper count (if we held it before) */
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if (blresult >= 0)
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{
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net_restorelock(count);
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}
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sched_unlock();
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leave_critical_section(flags);
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return ret;
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}
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/****************************************************************************
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* Name: net_lockedwait
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*
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* Description:
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* Atomically wait for sem while temporarily releasing the network lock.
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*
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* Caution should be utilized. Because the network lock is relinquished
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* during the wait, there could changes in the network state that occur
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* before the lock is recovered. Your design should account for this
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* possibility.
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*
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* Input Parameters:
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* sem - A reference to the semaphore to be taken.
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*
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* Returned Value:
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* Zero (OK) is returned on success; a negated errno value is returned on
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* any failure.
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*
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****************************************************************************/
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int net_lockedwait(sem_t *sem)
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{
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return net_timedwait(sem, NULL);
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}
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/****************************************************************************
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* Name: net_ioballoc
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*
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* Description:
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* Allocate an IOB. If no IOBs are available, then atomically wait for
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* for the IOB while temporarily releasing the lock on the network.
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*
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* Caution should be utilized. Because the network lock is relinquished
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* during the wait, there could changes in the network state that occur
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* before the lock is recovered. Your design should account for this
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* possibility.
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*
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* Input Parameters:
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* throttled - An indication of the IOB allocation is "throttled"
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*
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* Returned Value:
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* A pointer to the newly allocated IOB is returned on success. NULL is
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* returned on any allocation failure.
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*
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****************************************************************************/
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#ifdef CONFIG_MM_IOB
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FAR struct iob_s *net_ioballoc(bool throttled)
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{
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FAR struct iob_s *iob;
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iob = iob_tryalloc(throttled);
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if (iob == NULL)
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{
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irqstate_t flags;
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unsigned int count;
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int blresult;
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/* There are no buffers available now. We will have to wait for one to
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* become available. But let's not do that with the network locked.
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*/
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flags = enter_critical_section();
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blresult = net_breaklock(&count);
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iob = iob_alloc(throttled);
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if (blresult >= 0)
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{
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net_restorelock(count);
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}
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leave_critical_section(flags);
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}
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return iob;
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}
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#endif
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