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mm/iob: fix some comment in https://github.com/apache/nuttx/pull/14764

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reason:
Since we decoupled counting and sem count,
we changed the meanings of three key global variables:

g_iob_count: A positive number indicates the available number
  of IOBs, while a negative number indicates the number of waiters in iob_alloc (when throttle == false).
g_throttle_wait: Represents the number of waiters in
  iob_alloc (when throttle == true), and it will not be negative.
g_qentry_wait: Represents the number of waiters for
  qentry, and it will not be negative.

Signed-off-by: hujun5 <hujun5@xiaomi.com>
This commit is contained in:
hujun5 2024-11-18 16:34:11 +08:00 committed by Xiang Xiao
parent f142d04b91
commit 9f835f63bd
9 changed files with 46 additions and 162 deletions
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10
include/nuttx/mm/iob.h
View file

@ -278,16 +278,6 @@ FAR struct iob_s *iob_alloc_with_data(FAR void *data, uint16_t size,
int iob_navail(bool throttled);
/****************************************************************************
* Name: iob_qentry_navail
*
* Description:
* Return the number of available IOB chains.
*
****************************************************************************/
int iob_qentry_navail(void);
/****************************************************************************
* Name: iob_free
*

12
mm/iob/iob.h
View file

@ -75,27 +75,27 @@ extern FAR struct iob_qentry_s *g_iob_freeqlist;
extern FAR struct iob_qentry_s *g_iob_qcommitted;
#endif
/* Counting semaphores that tracks the number of free IOBs/qentries */
/* semaphores that IOBs need wait */
extern sem_t g_iob_sem;
/* Counts free I/O buffers */
extern volatile int16_t g_iob_count;
extern int16_t g_iob_count;
#if CONFIG_IOB_THROTTLE > 0
extern sem_t g_throttle_sem;
/* Counts available I/O buffers when throttled */
/* Wait Counts for throttle */
extern volatile int16_t g_throttle_count;
extern int16_t g_throttle_wait;
#endif
#if CONFIG_IOB_NCHAINS > 0
extern sem_t g_qentry_sem;
/* Counts free I/O buffer queue containers */
/* Wait Counts for qentry */
extern volatile int16_t g_qentry_count;
extern int16_t g_qentry_wait;
#endif
extern volatile spinlock_t g_iob_lock;

64
mm/iob/iob_alloc.c
View file

@ -105,20 +105,9 @@ static FAR struct iob_s *iob_tryalloc_internal(bool throttled)
{
FAR struct iob_s *iob;
#if CONFIG_IOB_THROTTLE > 0
int16_t count;
#endif
int16_t count = (throttled ? g_iob_count - CONFIG_IOB_THROTTLE :
g_iob_count);
#if CONFIG_IOB_THROTTLE > 0
/* Select the count to check. */
count = (throttled ? g_throttle_count : g_iob_count);
#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.
*/
#if CONFIG_IOB_THROTTLE > 0
/* If there are free I/O buffers for this allocation */
if (count > 0)
@ -136,30 +125,9 @@ static FAR struct iob_s *iob_tryalloc_internal(bool throttled)
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_count--;
DEBUGASSERT(g_iob_count >= 0);
#if CONFIG_IOB_THROTTLE > 0
/* The throttle semaphore is used to throttle the number of
* free buffers that are available. It is used to prevent
* the overrunning of the free buffer list. Please note that
* it can only be decremented to zero, which indicates no
* throttled buffers are available.
*/
if (g_throttle_count > 0)
{
g_throttle_count--;
}
#endif
/* Put the I/O buffer in a known state */
iob->io_flink = NULL; /* Not in a chain */
@ -185,19 +153,16 @@ static FAR struct iob_s *iob_tryalloc_internal(bool throttled)
static FAR struct iob_s *iob_allocwait(bool throttled, unsigned int timeout)
{
FAR struct iob_s *iob;
FAR volatile int16_t *count;
irqstate_t flags;
FAR sem_t *sem;
clock_t start;
int ret = OK;
#if CONFIG_IOB_THROTTLE > 0
/* Select the semaphore count to check. */
/* Select the semaphore to wait. */
count = (throttled ? &g_throttle_count : &g_iob_count);
sem = (throttled ? &g_throttle_sem : &g_iob_sem);
#else
count = &g_iob_count;
sem = &g_iob_sem;
#endif
@ -209,20 +174,21 @@ static FAR struct iob_s *iob_allocwait(bool throttled, unsigned int timeout)
flags = spin_lock_irqsave(&g_iob_lock);
/* Try to get an I/O buffer. If successful, the semaphore count will be
* decremented atomically.
*/
/* Try to get an I/O buffer */
iob = iob_tryalloc_internal(throttled);
iob = iob_tryalloc_internal(throttled);
if (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.
*/
(*count)--;
#if CONFIG_IOB_THROTTLE > 0
if (throttled)
{
g_throttle_wait++;
}
else
#endif
{
g_iob_count--;
}
spin_unlock_irqrestore(&g_iob_lock, flags);

22
mm/iob/iob_alloc_qentry.c
View file

@ -97,16 +97,6 @@ static FAR struct iob_qentry_s *iob_tryalloc_qentry_internal(void)
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_count--;
DEBUGASSERT(g_qentry_count >= 0);
/* Put the I/O buffer in a known state */
iobq->qe_head = NULL; /* Nothing is contained */
@ -139,20 +129,16 @@ static FAR struct iob_qentry_s *iob_allocwait_qentry(void)
flags = spin_lock_irqsave(&g_iob_lock);
/* Try to get an I/O buffer chain container. If successful, the semaphore
* count will bedecremented atomically.
*/
/* Try to get an I/O buffer chain container. */
qentry = iob_tryalloc_qentry_internal();
if (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.
/* If not successful, We need to wait
* for an I/O buffer chain container to be released
*/
g_qentry_count--;
g_qentry_wait++;
spin_unlock_irqrestore(&g_iob_lock, flags);
ret = nxsem_wait_uninterruptible(&g_qentry_sem);
if (ret >= 0)

49
mm/iob/iob_free.c
View file

@ -141,47 +141,27 @@ FAR struct iob_s *iob_free(FAR struct iob_s *iob)
* cases.
*/
#if CONFIG_IOB_THROTTLE > 0
if ((g_iob_count < 0) ||
((g_iob_count >= CONFIG_IOB_THROTTLE) &&
(g_throttle_count < 0)))
#else
if (g_iob_count < 0)
#endif
{
FAR sem_t *sem;
g_iob_count++;
iob->io_flink = g_iob_committed;
g_iob_committed = iob;
#if CONFIG_IOB_THROTTLE > 0
if (g_iob_count < 0)
{
g_iob_count++;
sem = &g_iob_sem;
}
else
{
g_throttle_count++;
sem = &g_throttle_sem;
}
#else
g_iob_count++;
sem = &g_iob_sem;
#endif
spin_unlock_irqrestore(&g_iob_lock, flags);
nxsem_post(sem);
nxsem_post(&g_iob_sem);
}
#if CONFIG_IOB_THROTTLE > 0
else if (g_throttle_wait > 0 && g_iob_count >= CONFIG_IOB_THROTTLE)
{
iob->io_flink = g_iob_committed;
g_iob_committed = iob;
g_throttle_wait--;
spin_unlock_irqrestore(&g_iob_lock, flags);
nxsem_post(&g_throttle_sem);
}
#endif
else
{
g_iob_count++;
#if CONFIG_IOB_THROTTLE > 0
if (g_iob_count > CONFIG_IOB_THROTTLE)
{
g_throttle_count++;
}
#endif
iob->io_flink = g_iob_freelist;
g_iob_freelist = iob;
spin_unlock_irqrestore(&g_iob_lock, flags);
@ -189,11 +169,6 @@ FAR struct iob_s *iob_free(FAR struct iob_s *iob)
DEBUGASSERT(g_iob_count <= CONFIG_IOB_NBUFFERS);
#if CONFIG_IOB_THROTTLE > 0
DEBUGASSERT(g_throttle_count <=
(CONFIG_IOB_NBUFFERS - CONFIG_IOB_THROTTLE));
#endif
#ifdef CONFIG_IOB_NOTIFIER
/* Check if the IOB was claimed by a thread that is blocked waiting
* for an IOB.

5
mm/iob/iob_free_qentry.c
View file

@ -68,17 +68,16 @@ FAR struct iob_qentry_s *iob_free_qentry(FAR struct iob_qentry_s *iobq)
* iob_tryalloc_qentry()).
*/
if (g_qentry_count < 0)
if (g_qentry_wait > 0)
{
iobq->qe_flink = g_iob_qcommitted;
g_iob_qcommitted = iobq;
g_qentry_count++;
g_qentry_wait--;
spin_unlock_irqrestore(&g_iob_lock, flags);
nxsem_post(&g_qentry_sem);
}
else
{
g_qentry_count++;
iobq->qe_flink = g_iob_freeqlist;
g_iob_freeqlist = iobq;
spin_unlock_irqrestore(&g_iob_lock, flags);

13
mm/iob/iob_initialize.c
View file

@ -93,26 +93,25 @@ FAR struct iob_qentry_s *g_iob_qcommitted;
sem_t g_iob_sem = SEM_INITIALIZER(0);
/* Counting semaphores that tracks the number of free IOBs/qentries */
/* Counting that tracks the number of free IOBs/qentries */
volatile int16_t g_iob_count = CONFIG_IOB_NBUFFERS;
int16_t g_iob_count = CONFIG_IOB_NBUFFERS;
#if CONFIG_IOB_THROTTLE > 0
sem_t g_throttle_sem = SEM_INITIALIZER(0);
/* Counts available I/O buffers when throttled */
/* Wait Counts for throttle */
volatile int16_t g_throttle_count = CONFIG_IOB_NBUFFERS -
CONFIG_IOB_THROTTLE;
int16_t g_throttle_wait = 0;
#endif
#if CONFIG_IOB_NCHAINS > 0
sem_t g_qentry_sem = SEM_INITIALIZER(0);
/* Counts free I/O buffer queue containers */
/* Wait Counts for qentry */
volatile int16_t g_qentry_count = CONFIG_IOB_NCHAINS;
int16_t g_qentry_wait = 0;
#endif
volatile spinlock_t g_iob_lock = SP_UNLOCKED;

27
mm/iob/iob_navail.c
View file

@ -71,30 +71,3 @@ int iob_navail(bool throttled)
return ret;
}
/****************************************************************************
* Name: iob_qentry_navail
*
* Description:
* Return the number of available IOB chains.
*
****************************************************************************/
int iob_qentry_navail(void)
{
int ret;
#if CONFIG_IOB_NCHAINS > 0
/* Get the value of the IOB chain qentry counting semaphores */
ret = g_qentry_count;
if (ret < 0)
{
ret = 0;
}
#else
ret = 0;
#endif
return ret;
}

6
mm/iob/iob_statistics.c
View file

@ -68,12 +68,8 @@ void iob_getstats(FAR struct iob_stats_s *stats)
}
#if CONFIG_IOB_THROTTLE > 0
stats->nthrottle = g_throttle_count;
stats->nthrottle = (g_iob_count - CONFIG_IOB_THROTTLE);
if (stats->nthrottle < 0)
{
stats->nthrottle = -stats->nthrottle;
}
else
#endif
{
stats->nthrottle = 0;