111 lines
4.0 KiB
C
111 lines
4.0 KiB
C
/****************************************************************************
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* mm/iob/iob_free_qentry.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 <assert.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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#if CONFIG_IOB_NCHAINS > 0
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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_qentry
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*
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* Description:
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* Free the I/O buffer chain container by returning it to the free list.
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* 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_qentry_s *iob_free_qentry(FAR struct iob_qentry_s *iobq)
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{
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FAR struct iob_qentry_s *nextq = iobq->qe_flink;
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irqstate_t flags;
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/* Free the I/O buffer chain container by adding it to the head of the
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* free or the committed list. We don't know what context we are called
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* from so 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 chain, then put
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* the IOB chain 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_qentry()).
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*/
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if (g_qentry_sem.semcount < 0)
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{
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iobq->qe_flink = g_iob_qcommitted;
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g_iob_qcommitted = iobq;
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}
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else
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{
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iobq->qe_flink = g_iob_freeqlist;
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g_iob_freeqlist = iobq;
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}
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/* Signal that an I/O buffer chain container is available. If there
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* is a thread waiting for an I/O buffer chain container, this will
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* wake up exactly one thread. The semaphore count will correctly
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* indicated that the awakened task owns an I/O buffer chain container
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* and should find it in the committed list.
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*/
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nxsem_post(&g_qentry_sem);
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leave_critical_section(flags);
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/* And return the I/O buffer chain container after the one that was freed */
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return nextq;
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}
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#endif /* CONFIG_IOB_NCHAINS > 0 */
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