145 lines
4.8 KiB
C
145 lines
4.8 KiB
C
/****************************************************************************
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* mm/iob/iob_free.c
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*
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* Copyright (C) 2014, 2016-2017 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 <semaphore.h>
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#include <assert.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/mm/iob.h>
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#include "iob.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: iob_free
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*
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* Description:
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* Free the I/O buffer at the head of a buffer chain returning it to the
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* free list. The link to the next I/O buffer in the chain is return.
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*
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****************************************************************************/
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FAR struct iob_s *iob_free(FAR struct iob_s *iob)
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{
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FAR struct iob_s *next = iob->io_flink;
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irqstate_t flags;
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iobinfo("iob=%p io_pktlen=%u io_len=%u next=%p\n",
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iob, iob->io_pktlen, iob->io_len, next);
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/* Copy the data that only exists in the head of a I/O buffer chain into
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* the next entry.
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*/
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if (next != NULL)
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{
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/* Copy and decrement the total packet length, being careful to
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* do nothing too crazy.
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*/
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if (iob->io_pktlen > iob->io_len)
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{
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/* Adjust packet length and move it to the next entry */
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next->io_pktlen = iob->io_pktlen - iob->io_len;
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DEBUGASSERT(next->io_pktlen >= next->io_len);
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}
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else
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{
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/* This can only happen if the next entry is last entry in the
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* chain... and if it is empty
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*/
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next->io_pktlen = 0;
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DEBUGASSERT(next->io_len == 0 && next->io_flink == NULL);
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}
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iobinfo("next=%p io_pktlen=%u io_len=%u\n",
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next, next->io_pktlen, next->io_len);
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}
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/* Free the I/O buffer by adding it to the head of the free or the
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* committed list. We don't know what context we are called from so
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* we use extreme measures to protect the free list: We disable
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* interrupts very briefly.
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*/
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flags = enter_critical_section();
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/* Which list? If there is a task waiting for an IOB, then put
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* the IOB on either the free list or on the committed list where
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* it is reserved for that allocation (and not available to
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* iob_tryalloc()).
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*/
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if (g_iob_sem.semcount < 0)
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{
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iob->io_flink = g_iob_committed;
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g_iob_committed = iob;
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}
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else
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{
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iob->io_flink = g_iob_freelist;
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g_iob_freelist = iob;
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}
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/* Signal that an IOB is available. If there is a thread waiting
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* for an IOB, this will wake up exactly one thread. The semaphore
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* count will correctly indicated that the awakened task owns an
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* IOB and should find it in the committed list.
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*/
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sem_post(&g_iob_sem);
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#if CONFIG_IOB_THROTTLE > 0
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sem_post(&g_throttle_sem);
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#endif
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leave_critical_section(flags);
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/* And return the I/O buffer after the one that was freed */
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return next;
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}
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