267 lines
8.8 KiB
C
267 lines
8.8 KiB
C
/****************************************************************************
|
|
* mm/iob/iob_alloc_qentry.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/mm/iob.h>
|
|
|
|
#include "iob.h"
|
|
|
|
#if CONFIG_IOB_NCHAINS > 0
|
|
|
|
/****************************************************************************
|
|
* Private Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: iob_alloc_qcommitted
|
|
*
|
|
* Description:
|
|
* Allocate an I/O buffer by taking the buffer at the head of the committed
|
|
* list.
|
|
*
|
|
****************************************************************************/
|
|
|
|
static FAR struct iob_qentry_s *iob_alloc_qcommitted(void)
|
|
{
|
|
FAR struct iob_qentry_s *iobq = 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 */
|
|
|
|
iobq = g_iob_qcommitted;
|
|
if (iobq != NULL)
|
|
{
|
|
/* Remove the I/O buffer from the committed list */
|
|
|
|
g_iob_qcommitted = iobq->qe_flink;
|
|
|
|
/* Put the I/O buffer in a known state */
|
|
|
|
iobq->qe_head = NULL; /* Nothing is contained */
|
|
}
|
|
|
|
leave_critical_section(flags);
|
|
return iobq;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: iob_allocwait_qentry
|
|
*
|
|
* Description:
|
|
* Allocate an I/O buffer chain container by taking the buffer at the head
|
|
* of the free list. This function is intended only for internal use by
|
|
* the IOB module.
|
|
*
|
|
****************************************************************************/
|
|
|
|
static FAR struct iob_qentry_s *iob_allocwait_qentry(void)
|
|
{
|
|
FAR struct iob_qentry_s *qentry;
|
|
irqstate_t flags;
|
|
int ret = OK;
|
|
|
|
/* The following must be atomic; interrupt must be disabled so that there
|
|
* is no conflict with interrupt level I/O buffer chain container
|
|
* 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 chain container. If successful, the semaphore
|
|
* count will bedecremented atomically.
|
|
*/
|
|
|
|
qentry = iob_tryalloc_qentry();
|
|
while (ret == OK && qentry == 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 chain container to be released when the
|
|
* semaphore count will be incremented.
|
|
*/
|
|
|
|
ret = nxsem_wait(&g_qentry_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
|
|
* is 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 chain container was
|
|
* freed and we hold a count for one IOB. Unless somehting
|
|
* failed, we should have an IOB waiting for us in the
|
|
* committed list.
|
|
*/
|
|
|
|
qentry = iob_alloc_qcommitted();
|
|
DEBUGASSERT(qentry != NULL);
|
|
|
|
if (qentry == NULL)
|
|
{
|
|
/* This should not fail, but we allow for that possibility to
|
|
* handle any potential, non-obvious race condition. Perhaps
|
|
* the free IOB ended up in the g_iob_free list?
|
|
*
|
|
* 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(&g_qentry_sem);
|
|
qentry = iob_tryalloc_qentry();
|
|
}
|
|
}
|
|
}
|
|
|
|
leave_critical_section(flags);
|
|
return qentry;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: iob_alloc_qentry
|
|
*
|
|
* Description:
|
|
* Allocate an I/O buffer chain container by taking the buffer at the head
|
|
* of the free list. This function is intended only for internal use by
|
|
* the IOB module.
|
|
*
|
|
****************************************************************************/
|
|
|
|
FAR struct iob_qentry_s *iob_alloc_qentry(void)
|
|
{
|
|
/* 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_qentry();
|
|
}
|
|
else
|
|
{
|
|
/* Then allocate an I/O buffer, waiting as necessary */
|
|
|
|
return iob_allocwait_qentry();
|
|
}
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: iob_tryalloc_qentry
|
|
*
|
|
* Description:
|
|
* Try to allocate an I/O buffer chain container by taking the buffer at
|
|
* the head of the free list without waiting for the container to become
|
|
* free. This function is intended only for internal use by the IOB module.
|
|
*
|
|
****************************************************************************/
|
|
|
|
FAR struct iob_qentry_s *iob_tryalloc_qentry(void)
|
|
{
|
|
FAR struct iob_qentry_s *iobq;
|
|
irqstate_t flags;
|
|
|
|
/* 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();
|
|
iobq = g_iob_freeqlist;
|
|
if (iobq)
|
|
{
|
|
/* Remove the I/O buffer chain container from the free list and
|
|
* decrement the counting semaphore that tracks the number of free
|
|
* containers.
|
|
*/
|
|
|
|
g_iob_freeqlist = iobq->qe_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_qentry_sem.semcount--;
|
|
DEBUGASSERT(g_qentry_sem.semcount >= 0);
|
|
|
|
/* Put the I/O buffer in a known state */
|
|
|
|
iobq->qe_head = NULL; /* Nothing is contained */
|
|
}
|
|
|
|
leave_critical_section(flags);
|
|
return iobq;
|
|
}
|
|
|
|
#endif /* CONFIG_IOB_NCHAINS > 0 */
|