242 lines
7.2 KiB
C
242 lines
7.2 KiB
C
/****************************************************************************
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* mm/iob/iob_free.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 <stdbool.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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#ifdef CONFIG_IOB_ALLOC
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# include <nuttx/kmalloc.h>
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#endif
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#include <nuttx/mm/iob.h>
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#include "iob.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#ifdef CONFIG_IOB_NOTIFIER
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# if !defined(CONFIG_IOB_NOTIFIER_DIV) || CONFIG_IOB_NOTIFIER_DIV < 2
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# define IOB_DIVIDER 1
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# elif CONFIG_IOB_NOTIFIER_DIV < 4
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# define IOB_DIVIDER 2
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# elif CONFIG_IOB_NOTIFIER_DIV < 8
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# define IOB_DIVIDER 4
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# elif CONFIG_IOB_NOTIFIER_DIV < 16
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# define IOB_DIVIDER 8
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# elif CONFIG_IOB_NOTIFIER_DIV < 32
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# define IOB_DIVIDER 16
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# elif CONFIG_IOB_NOTIFIER_DIV < 64
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# define IOB_DIVIDER 32
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# else
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# define IOB_DIVIDER 64
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# endif
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#endif
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#define IOB_MASK (IOB_DIVIDER - 1)
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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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#ifdef CONFIG_IOB_NOTIFIER
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int16_t navail;
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#endif
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#if CONFIG_IOB_THROTTLE > 0
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bool committed_thottled = false;
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#endif
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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 free entry isn't first entry in the
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* chain...
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*/
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next->io_pktlen = 0;
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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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#ifdef CONFIG_IOB_ALLOC
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if (iob->io_free != NULL)
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{
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iob->io_free(iob->io_data);
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kmm_free(iob);
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return next;
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}
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#endif
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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 = spin_lock_irqsave(&g_iob_lock);
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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()). This is true for both throttled and non-throttled
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* cases.
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*/
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#if CONFIG_IOB_THROTTLE > 0
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if ((g_iob_sem.semcount < 0) ||
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((g_iob_sem.semcount >= CONFIG_IOB_THROTTLE) &&
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(g_throttle_sem.semcount < 0)))
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#else
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if (g_iob_sem.semcount < 0)
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#endif
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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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#if CONFIG_IOB_THROTTLE > 0
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if ((g_iob_sem.semcount >= CONFIG_IOB_THROTTLE) &&
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(g_throttle_sem.semcount < 0))
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{
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committed_thottled = true;
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}
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#endif
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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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spin_unlock_irqrestore(&g_iob_lock, flags);
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/* Signal that an IOB is available. This is done with schedule locked
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* to make sure that both g_iob_sem and g_throttle_sem are incremented
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* together (if applicable). After the schedule is unlocked, if there
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* is a thread blocked, waiting for an IOB, this will wake up exactly
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* one thread. The semaphore count will correctly indicate that the
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* awakened task owns an IOB and should find it in the committed list.
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*/
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sched_lock();
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nxsem_post(&g_iob_sem);
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DEBUGASSERT(g_iob_sem.semcount <= CONFIG_IOB_NBUFFERS);
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#if CONFIG_IOB_THROTTLE > 0
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flags = spin_lock_irqsave(&g_iob_lock);
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if (g_iob_sem.semcount > CONFIG_IOB_THROTTLE)
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{
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/* If posting to the the throttled semaphore is going to awake a
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* waiting task, then the g_iob_sem count should be decremented
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* because an I/O buffer (from the head of the g_iob_committed list)
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* will be allocated to this waiting task.
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* Decrementing the g_throttled_sem (when posting to the g_iob_sem)
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* is not necessary because this condition can only occur when the
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* g_throttled_sem is less or equal to zero. On the other hand, if
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* the g_iob_sem is greater than the CONFIG_IOB_THROTTLE and there
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* is a waiting thread, then the I/O buffer just freed will be
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* committed to a waiting task and is not available for general use.
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*/
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if (committed_thottled)
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{
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g_iob_sem.semcount--;
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}
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spin_unlock_irqrestore(&g_iob_lock, flags);
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nxsem_post(&g_throttle_sem);
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DEBUGASSERT(g_throttle_sem.semcount <=
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(CONFIG_IOB_NBUFFERS - CONFIG_IOB_THROTTLE));
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}
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else
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{
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spin_unlock_irqrestore(&g_iob_lock, flags);
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}
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#endif
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sched_unlock();
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#ifdef CONFIG_IOB_NOTIFIER
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/* Check if the IOB was claimed by a thread that is blocked waiting
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* for an IOB.
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*/
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navail = iob_navail(false);
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if (navail > 0 && (navail & IOB_MASK) == 0)
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{
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/* Signal any threads that have requested a signal notification
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* when an IOB becomes available.
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*/
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iob_notifier_signal();
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}
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#endif
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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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