98 lines
3.2 KiB
C
98 lines
3.2 KiB
C
/****************************************************************************
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* mm/iob/iob_free_qentry.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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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