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- /****************************************************************************
- * mm/iob/iob_alloc.c
- *
- * Copyright (C) 2014, 2016-2017 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- * used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <semaphore.h>
- #include <assert.h>
- #include <errno.h>
- #include <nuttx/irq.h>
- #include <nuttx/arch.h>
- #include <nuttx/sched.h>
- #include <nuttx/mm/iob.h>
- #include "iob.h"
- /****************************************************************************
- * Private Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: iob_alloc_committed
- *
- * Description:
- * Allocate an I/O buffer by taking the buffer at the head of the committed
- * list.
- *
- ****************************************************************************/
- static FAR struct iob_s *iob_alloc_committed(enum iob_user_e consumerid)
- {
- FAR struct iob_s *iob = NULL;
- irqstate_t flags;
- /* We don't know what context we are called from so we use extreme measures
- * to protect the committed list: We disable interrupts very briefly.
- */
- flags = enter_critical_section();
- /* Take the I/O buffer from the head of the committed list */
- iob = g_iob_committed;
- if (iob != NULL)
- {
- /* Remove the I/O buffer from the committed list */
- g_iob_committed = iob->io_flink;
- /* Put the I/O buffer in a known state */
- iob->io_flink = NULL; /* Not in a chain */
- iob->io_len = 0; /* Length of the data in the entry */
- iob->io_offset = 0; /* Offset to the beginning of data */
- iob->io_pktlen = 0; /* Total length of the packet */
- #if !defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_PROCFS) && \
- defined(CONFIG_MM_IOB) && !defined(CONFIG_FS_PROCFS_EXCLUDE_IOBINFO)
- iob_stats_onalloc(consumerid);
- #endif
- }
- leave_critical_section(flags);
- return iob;
- }
- /****************************************************************************
- * Name: iob_allocwait
- *
- * Description:
- * Allocate an I/O buffer, waiting if necessary. This function cannot be
- * called from any interrupt level logic.
- *
- ****************************************************************************/
- static FAR struct iob_s *iob_allocwait(bool throttled,
- enum iob_user_e consumerid)
- {
- FAR struct iob_s *iob;
- irqstate_t flags;
- FAR sem_t *sem;
- int ret = OK;
- #if CONFIG_IOB_THROTTLE > 0
- /* Select the semaphore count to check. */
- sem = (throttled ? &g_throttle_sem : &g_iob_sem);
- #else
- sem = &g_iob_sem;
- #endif
- /* The following must be atomic; interrupt must be disabled so that there
- * is no conflict with interrupt level I/O buffer allocations. This is
- * not as bad as it sounds because interrupts will be re-enabled while
- * we are waiting for I/O buffers to become free.
- */
- flags = enter_critical_section();
- /* Try to get an I/O buffer. If successful, the semaphore count will be
- * decremented atomically.
- */
- iob = iob_tryalloc(throttled, consumerid);
- while (ret == OK && iob == NULL)
- {
- /* If not successful, then the semaphore count was less than or equal
- * to zero (meaning that there are no free buffers). We need to wait
- * for an I/O buffer to be released and placed in the committed
- * list.
- */
- ret = nxsem_wait(sem);
- if (ret < 0)
- {
- /* EINTR is not an error! EINTR simply means that we were
- * awakened by a signal and we should try again.
- *
- * REVISIT: Many end-user interfaces are required to return with
- * an error if EINTR is set. Most uses of this function are in
- * internal, non-user logic. But are there cases where the error
- * should be returned.
- */
- if (ret == -EINTR)
- {
- /* Force a success indication so that we will continue looping. */
- ret = OK;
- }
- }
- else
- {
- /* When we wake up from wait successfully, an I/O buffer was
- * freed and we hold a count for one IOB.
- */
- iob = iob_alloc_committed(consumerid);
- if (iob == NULL)
- {
- /* We need release our count so that it is available to
- * iob_tryalloc(), perhaps allowing another thread to take our
- * count. In that event, iob_tryalloc() will fail above and
- * we will have to wait again.
- */
- nxsem_post(sem);
- iob = iob_tryalloc(throttled, consumerid);
- }
- /* REVISIT: I think this logic should be moved inside of
- * iob_alloc_committed, so that it can exist inside of the critical
- * section along with all other sem count changes.
- */
- #if CONFIG_IOB_THROTTLE > 0
- else
- {
- if (throttled)
- {
- g_iob_sem.semcount--;
- }
- else
- {
- g_throttle_sem.semcount--;
- }
- }
- #endif
- }
- }
- leave_critical_section(flags);
- return iob;
- }
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: iob_alloc
- *
- * Description:
- * Allocate an I/O buffer by taking the buffer at the head of the free list.
- *
- ****************************************************************************/
- FAR struct iob_s *iob_alloc(bool throttled, enum iob_user_e consumerid)
- {
- /* Were we called from the interrupt level? */
- if (up_interrupt_context() || sched_idletask())
- {
- /* Yes, then try to allocate an I/O buffer without waiting */
- return iob_tryalloc(throttled, consumerid);
- }
- else
- {
- /* Then allocate an I/O buffer, waiting as necessary */
- return iob_allocwait(throttled, consumerid);
- }
- }
- /****************************************************************************
- * Name: iob_tryalloc
- *
- * Description:
- * Try to allocate an I/O buffer by taking the buffer at the head of the
- * free list without waiting for a buffer to become free.
- *
- ****************************************************************************/
- FAR struct iob_s *iob_tryalloc(bool throttled, enum iob_user_e consumerid)
- {
- FAR struct iob_s *iob;
- irqstate_t flags;
- #if CONFIG_IOB_THROTTLE > 0
- FAR sem_t *sem;
- #endif
- #if CONFIG_IOB_THROTTLE > 0
- /* Select the semaphore count to check. */
- sem = (throttled ? &g_throttle_sem : &g_iob_sem);
- #endif
- /* We don't know what context we are called from so we use extreme measures
- * to protect the free list: We disable interrupts very briefly.
- */
- flags = enter_critical_section();
- #if CONFIG_IOB_THROTTLE > 0
- /* If there are free I/O buffers for this allocation */
- if (sem->semcount > 0)
- #endif
- {
- /* Take the I/O buffer from the head of the free list */
- iob = g_iob_freelist;
- if (iob != NULL)
- {
- /* Remove the I/O buffer from the free list and decrement the
- * counting semaphore(s) that tracks the number of available
- * IOBs.
- */
- g_iob_freelist = iob->io_flink;
- /* Take a semaphore count. Note that we cannot do this in
- * in the orthodox way by calling nxsem_wait() or nxsem_trywait()
- * because this function may be called from an interrupt
- * handler. Fortunately we know at at least one free buffer
- * so a simple decrement is all that is needed.
- */
- g_iob_sem.semcount--;
- DEBUGASSERT(g_iob_sem.semcount >= 0);
- #if CONFIG_IOB_THROTTLE > 0
- /* The throttle semaphore is a little more complicated because
- * it can be negative! Decrementing is still safe, however.
- */
- g_throttle_sem.semcount--;
- DEBUGASSERT(g_throttle_sem.semcount >= -CONFIG_IOB_THROTTLE);
- #endif
- #if !defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_PROCFS) && \
- defined(CONFIG_MM_IOB) && !defined(CONFIG_FS_PROCFS_EXCLUDE_IOBINFO)
- iob_stats_onalloc(consumerid);
- #endif
- leave_critical_section(flags);
- /* Put the I/O buffer in a known state */
- iob->io_flink = NULL; /* Not in a chain */
- iob->io_len = 0; /* Length of the data in the entry */
- iob->io_offset = 0; /* Offset to the beginning of data */
- iob->io_pktlen = 0; /* Total length of the packet */
- return iob;
- }
- }
- leave_critical_section(flags);
- return NULL;
- }
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