309 lines
9.8 KiB
C
309 lines
9.8 KiB
C
/****************************************************************************
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* mm/iob/iob_alloc.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 <errno.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/sched.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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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: iob_alloc_committed
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*
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* Description:
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* Allocate an I/O buffer by taking the buffer at the head of the committed
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* list.
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*
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****************************************************************************/
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static FAR struct iob_s *iob_alloc_committed(enum iob_user_e consumerid)
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{
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FAR struct iob_s *iob = NULL;
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irqstate_t flags;
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/* We don't know what context we are called from so we use extreme measures
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* to protect the committed list: We disable interrupts very briefly.
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*/
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flags = enter_critical_section();
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/* Take the I/O buffer from the head of the committed list */
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iob = g_iob_committed;
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if (iob != NULL)
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{
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/* Remove the I/O buffer from the committed list */
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g_iob_committed = iob->io_flink;
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/* Put the I/O buffer in a known state */
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iob->io_flink = NULL; /* Not in a chain */
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iob->io_len = 0; /* Length of the data in the entry */
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iob->io_offset = 0; /* Offset to the beginning of data */
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iob->io_pktlen = 0; /* Total length of the packet */
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#if !defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_PROCFS) && \
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defined(CONFIG_MM_IOB) && !defined(CONFIG_FS_PROCFS_EXCLUDE_IOBINFO)
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iob_stats_onalloc(consumerid);
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#endif
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}
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leave_critical_section(flags);
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return iob;
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}
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/****************************************************************************
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* Name: iob_allocwait
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*
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* Description:
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* Allocate an I/O buffer, waiting if necessary. This function cannot be
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* called from any interrupt level logic.
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*
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****************************************************************************/
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static FAR struct iob_s *iob_allocwait(bool throttled,
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enum iob_user_e consumerid)
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{
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FAR struct iob_s *iob;
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irqstate_t flags;
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FAR sem_t *sem;
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int ret = OK;
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#if CONFIG_IOB_THROTTLE > 0
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/* Select the semaphore count to check. */
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sem = (throttled ? &g_throttle_sem : &g_iob_sem);
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#else
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sem = &g_iob_sem;
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#endif
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/* The following must be atomic; interrupt must be disabled so that there
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* is no conflict with interrupt level I/O buffer allocations. This is
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* not as bad as it sounds because interrupts will be re-enabled while
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* we are waiting for I/O buffers to become free.
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*/
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flags = enter_critical_section();
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/* Try to get an I/O buffer. If successful, the semaphore count will be
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* decremented atomically.
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*/
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iob = iob_tryalloc(throttled, consumerid);
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while (ret == OK && iob == NULL)
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{
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/* If not successful, then the semaphore count was less than or equal
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* to zero (meaning that there are no free buffers). We need to wait
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* for an I/O buffer to be released and placed in the committed
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* list.
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*/
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ret = nxsem_wait_uninterruptible(sem);
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if (ret >= 0)
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{
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/* When we wake up from wait successfully, an I/O buffer was
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* freed and we hold a count for one IOB.
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*/
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iob = iob_alloc_committed(consumerid);
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if (iob == NULL)
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{
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/* We need release our count so that it is available to
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* iob_tryalloc(), perhaps allowing another thread to take our
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* count. In that event, iob_tryalloc() will fail above and
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* we will have to wait again.
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*/
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nxsem_post(sem);
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iob = iob_tryalloc(throttled, consumerid);
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}
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/* REVISIT: I think this logic should be moved inside of
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* iob_alloc_committed, so that it can exist inside of the critical
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* section along with all other sem count changes.
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*/
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#if CONFIG_IOB_THROTTLE > 0
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else
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{
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if (throttled)
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{
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g_iob_sem.semcount--;
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}
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else
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{
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g_throttle_sem.semcount--;
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}
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}
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#endif
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}
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}
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leave_critical_section(flags);
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return iob;
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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: iob_alloc
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*
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* Description:
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* Allocate an I/O buffer by taking the buffer at the head of the free list.
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*
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****************************************************************************/
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FAR struct iob_s *iob_alloc(bool throttled, enum iob_user_e consumerid)
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{
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/* Were we called from the interrupt level? */
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if (up_interrupt_context() || sched_idletask())
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{
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/* Yes, then try to allocate an I/O buffer without waiting */
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return iob_tryalloc(throttled, consumerid);
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}
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else
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{
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/* Then allocate an I/O buffer, waiting as necessary */
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return iob_allocwait(throttled, consumerid);
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}
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}
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/****************************************************************************
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* Name: iob_tryalloc
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*
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* Description:
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* Try to allocate an I/O buffer by taking the buffer at the head of the
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* free list without waiting for a buffer to become free.
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*
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****************************************************************************/
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FAR struct iob_s *iob_tryalloc(bool throttled, enum iob_user_e consumerid)
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{
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FAR struct iob_s *iob;
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irqstate_t flags;
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#if CONFIG_IOB_THROTTLE > 0
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FAR sem_t *sem;
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#endif
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#if CONFIG_IOB_THROTTLE > 0
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/* Select the semaphore count to check. */
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sem = (throttled ? &g_throttle_sem : &g_iob_sem);
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#endif
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/* We don't know what context we are called from so we use extreme measures
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* to protect the free list: We disable interrupts very briefly.
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*/
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flags = enter_critical_section();
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#if CONFIG_IOB_THROTTLE > 0
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/* If there are free I/O buffers for this allocation */
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if (sem->semcount > 0)
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#endif
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{
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/* Take the I/O buffer from the head of the free list */
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iob = g_iob_freelist;
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if (iob != NULL)
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{
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/* Remove the I/O buffer from the free list and decrement the
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* counting semaphore(s) that tracks the number of available
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* IOBs.
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*/
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g_iob_freelist = iob->io_flink;
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/* Take a semaphore count. Note that we cannot do this in
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* in the orthodox way by calling nxsem_wait() or nxsem_trywait()
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* because this function may be called from an interrupt
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* handler. Fortunately we know at at least one free buffer
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* so a simple decrement is all that is needed.
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*/
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g_iob_sem.semcount--;
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DEBUGASSERT(g_iob_sem.semcount >= 0);
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#if CONFIG_IOB_THROTTLE > 0
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/* The throttle semaphore is a little more complicated because
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* it can be negative! Decrementing is still safe, however.
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*/
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g_throttle_sem.semcount--;
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DEBUGASSERT(g_throttle_sem.semcount >= -CONFIG_IOB_THROTTLE);
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#endif
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#if !defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_PROCFS) && \
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defined(CONFIG_MM_IOB) && !defined(CONFIG_FS_PROCFS_EXCLUDE_IOBINFO)
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iob_stats_onalloc(consumerid);
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#endif
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leave_critical_section(flags);
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/* Put the I/O buffer in a known state */
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iob->io_flink = NULL; /* Not in a chain */
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iob->io_len = 0; /* Length of the data in the entry */
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iob->io_offset = 0; /* Offset to the beginning of data */
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iob->io_pktlen = 0; /* Total length of the packet */
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return iob;
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}
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}
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leave_critical_section(flags);
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return NULL;
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}
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