9568600ab1
This commit backs out most of commit b4747286b1. That change was added because sem_wait() would sometimes cause cancellation points inappropriated. But with these recent changes, nxsem_wait() is used instead and it is not a cancellation point.
In the OS, all calls to sem_wait() changed to nxsem_wait(). nxsem_wait() does not return errors via errno so each place where nxsem_wait() is now called must not examine the errno variable.
In all OS functions (not libraries), change sem_wait() to nxsem_wait(). This will prevent the OS from creating bogus cancellation points and from modifying the per-task errno variable.
sched/semaphore: Add the function nxsem_wait(). This is a new internal OS interface. It is functionally equivalent to sem_wait() except that (1) it is not a cancellation point, and (2) it does not set the per-thread errno value on return.
1206 lines
36 KiB
C
1206 lines
36 KiB
C
/****************************************************************************
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* sched/semaphore/sem_holder.c
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*
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* Copyright (C) 2009-2011, 2013, 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 <semaphore.h>
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#include <sched.h>
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#include <assert.h>
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#include <debug.h>
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#include <nuttx/arch.h>
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#include "sched/sched.h"
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#include "semaphore/semaphore.h"
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Configuration ************************************************************/
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#ifndef CONFIG_SEM_PREALLOCHOLDERS
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# define CONFIG_SEM_PREALLOCHOLDERS 0
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#endif
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/****************************************************************************
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* Private Type Declarations
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****************************************************************************/
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typedef int (*holderhandler_t)(FAR struct semholder_s *pholder,
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FAR sem_t *sem, FAR void *arg);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/* Preallocated holder structures */
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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static struct semholder_s g_holderalloc[CONFIG_SEM_PREALLOCHOLDERS];
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static FAR struct semholder_s *g_freeholders;
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#endif
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/****************************************************************************
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* Name: nxsem_allocholder
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****************************************************************************/
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static inline FAR struct semholder_s *nxsem_allocholder(sem_t *sem)
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{
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FAR struct semholder_s *pholder;
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/* Check if the "built-in" holder is being used. We have this built-in
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* holder to optimize for the simplest case where semaphores are only
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* used to implement mutexes.
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*/
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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pholder = g_freeholders;
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if (pholder != NULL)
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{
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/* Remove the holder from the free list an put it into the semaphore's
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* holder list
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*/
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g_freeholders = pholder->flink;
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pholder->flink = sem->hhead;
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sem->hhead = pholder;
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/* Make sure the initial count is zero */
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pholder->counts = 0;
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}
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#else
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if (sem->holder[0].htcb == NULL)
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{
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pholder = &sem->holder[0];
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pholder->counts = 0;
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}
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else if (sem->holder[1].htcb == NULL)
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{
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pholder = &sem->holder[1];
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pholder->counts = 0;
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}
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#endif
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else
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{
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serr("ERROR: Insufficient pre-allocated holders\n");
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pholder = NULL;
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}
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DEBUGASSERT(pholder != NULL);
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return pholder;
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}
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/****************************************************************************
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* Name: nxsem_findholder
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****************************************************************************/
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static FAR struct semholder_s *nxsem_findholder(sem_t *sem,
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FAR struct tcb_s *htcb)
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{
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FAR struct semholder_s *pholder;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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/* Try to find the holder in the list of holders associated with this
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* semaphore
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*/
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for (pholder = sem->hhead; pholder != NULL; pholder = pholder->flink)
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{
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if (pholder->htcb == htcb)
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{
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/* Got it! */
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return pholder;
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}
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}
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#else
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int i;
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pholder = NULL;
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/* We have two hard-allocated holder structures in sem_t */
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for (i = 0; i < 2; i++)
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{
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pholder = &sem->holder[i];
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if (pholder->htcb == htcb)
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{
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/* Got it! */
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return pholder;
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}
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}
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#endif
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/* The holder does not appear in the list */
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return NULL;
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}
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/****************************************************************************
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* Name: nxsem_findorallocateholder
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****************************************************************************/
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static inline FAR struct semholder_s *
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nxsem_findorallocateholder(sem_t *sem, FAR struct tcb_s *htcb)
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{
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FAR struct semholder_s *pholder = nxsem_findholder(sem, htcb);
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if (!pholder)
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{
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pholder = nxsem_allocholder(sem);
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}
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return pholder;
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}
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/****************************************************************************
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* Name: nxsem_freeholder
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****************************************************************************/
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static inline void nxsem_freeholder(sem_t *sem,
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FAR struct semholder_s *pholder)
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{
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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FAR struct semholder_s *curr;
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FAR struct semholder_s *prev;
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#endif
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/* Release the holder and counts */
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pholder->htcb = NULL;
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pholder->counts = 0;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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/* Search the list for the matching holder */
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for (prev = NULL, curr = sem->hhead;
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curr && curr != pholder;
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prev = curr, curr = curr->flink);
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if (curr != NULL)
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{
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/* Remove the holder from the list */
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if (prev != NULL)
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{
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prev->flink = pholder->flink;
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}
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else
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{
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sem->hhead = pholder->flink;
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}
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/* And put it in the free list */
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pholder->flink = g_freeholders;
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g_freeholders = pholder;
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}
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#endif
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}
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/****************************************************************************
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* Name: nxsem_findandfreeholder
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****************************************************************************/
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static inline void nxsem_findandfreeholder(sem_t *sem, FAR struct tcb_s *htcb)
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{
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FAR struct semholder_s *pholder = nxsem_findholder(sem, htcb);
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/* When no more counts are held, remove the holder from the list. The
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* count was decremented in nxsem_releaseholder.
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*/
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if (pholder != NULL && pholder->counts <= 0)
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{
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nxsem_freeholder(sem, pholder);
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}
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}
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/****************************************************************************
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* Name: nxsem_foreachholder
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****************************************************************************/
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static int nxsem_foreachholder(FAR sem_t *sem, holderhandler_t handler,
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FAR void *arg)
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{
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FAR struct semholder_s *pholder;
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int ret = 0;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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FAR struct semholder_s *next;
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for (pholder = sem->hhead; pholder && ret == 0; pholder = next)
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{
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/* In case this holder gets deleted */
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next = pholder->flink;
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/* Check if there is a handler... there should always be one
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* in this configuration.
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*/
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if (pholder->htcb != NULL)
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{
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/* Call the handler */
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ret = handler(pholder, sem, arg);
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}
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}
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#else
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int i;
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/* We have two hard-allocated holder structures in sem_t */
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for (i = 0; i < 2; i++)
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{
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pholder = &sem->holder[i];
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/* The hard-allocated containers may hold a NULL holder */
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if (pholder->htcb != NULL)
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{
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/* Call the handler */
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ret = handler(pholder, sem, arg);
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}
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}
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#endif
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return ret;
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}
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/****************************************************************************
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* Name: nxsem_recoverholders
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****************************************************************************/
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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static int nxsem_recoverholders(FAR struct semholder_s *pholder,
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FAR sem_t *sem, FAR void *arg)
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{
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nxsem_freeholder(sem, pholder);
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return 0;
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}
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#endif
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/****************************************************************************
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* Name: nxsem_boostholderprio
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****************************************************************************/
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static int nxsem_boostholderprio(FAR struct semholder_s *pholder,
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FAR sem_t *sem, FAR void *arg)
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{
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FAR struct tcb_s *htcb = (FAR struct tcb_s *)pholder->htcb;
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FAR struct tcb_s *rtcb = (FAR struct tcb_s *)arg;
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/* Make sure that the holder thread is still active. If it exited without
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* releasing its counts, then that would be a bad thing. But we can take
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* no real action because we don't know know that the program is doing.
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* Perhaps its plan is to kill a thread, then destroy the semaphore.
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*/
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if (!sched_verifytcb(htcb))
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{
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serr("ERROR: TCB 0x%08x is a stale handle, counts lost\n", htcb);
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DEBUGPANIC();
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nxsem_freeholder(sem, pholder);
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}
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#if CONFIG_SEM_NNESTPRIO > 0
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/* If the priority of the thread that is waiting for a count is greater
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* than the base priority of the thread holding a count, then we may need
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* to adjust the holder's priority now or later to that priority.
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*/
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else if (rtcb->sched_priority > htcb->base_priority)
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{
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/* If the new priority is greater than the current, possibly already
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* boosted priority of the holder thread, then we will have to raise
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* the holder's priority now.
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*/
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if (rtcb->sched_priority > htcb->sched_priority)
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{
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/* If the current priority of holder thread has already been
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* boosted, then add the boost priority to the list of restoration
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* priorities. When the higher priority waiter thread gets its
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* count, then we need to revert the holder thread to this saved
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* priority (not to its base priority).
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*/
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if (htcb->sched_priority > htcb->base_priority)
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{
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/* Save the current, boosted priority of the holder thread. */
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if (htcb->npend_reprio < CONFIG_SEM_NNESTPRIO)
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{
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htcb->pend_reprios[htcb->npend_reprio] = htcb->sched_priority;
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htcb->npend_reprio++;
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}
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else
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{
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serr("ERROR: CONFIG_SEM_NNESTPRIO exceeded\n");
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DEBUGASSERT(htcb->npend_reprio < CONFIG_SEM_NNESTPRIO);
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}
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}
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/* Raise the priority of the thread holding of the semaphore.
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* This cannot cause a context switch because we have preemption
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* disabled. The holder thread may be marked "pending" and the
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* switch may occur during up_block_task() processing.
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*/
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(void)sched_setpriority(htcb, rtcb->sched_priority);
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}
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else
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{
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/* The new priority is above the base priority of the holder,
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* but not as high as its current working priority. Just put it
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* in the list of pending restoration priorities so that when the
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* higher priority thread gets its count, we can revert to this
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* saved priority and not to the base priority.
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*/
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if (htcb->npend_reprio < CONFIG_SEM_NNESTPRIO)
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{
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htcb->pend_reprios[htcb->npend_reprio] = rtcb->sched_priority;
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htcb->npend_reprio++;
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}
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else
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{
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serr("ERROR: CONFIG_SEM_NNESTPRIO exceeded\n");
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DEBUGASSERT(htcb->npend_reprio < CONFIG_SEM_NNESTPRIO);
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}
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}
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}
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#else
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/* If the priority of the thread that is waiting for a count is less than
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* of equal to the priority of the thread holding a count, then do nothing
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* because the thread is already running at a sufficient priority.
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*/
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else if (rtcb->sched_priority > htcb->sched_priority)
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{
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/* Raise the priority of the holder of the semaphore. This
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* cannot cause a context switch because we have preemption
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* disabled. The task will be marked "pending" and the switch
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* will occur during up_block_task() processing.
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*/
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(void)sched_setpriority(htcb, rtcb->sched_priority);
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}
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#endif
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return 0;
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}
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/****************************************************************************
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* Name: nxsem_verifyholder
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****************************************************************************/
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#ifdef CONFIG_DEBUG_ASSERTIONS
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static int nxsem_verifyholder(FAR struct semholder_s *pholder,
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FAR sem_t *sem, FAR void *arg)
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{
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#if 0 /* Need to revisit this, but these assumptions seem to be untrue -- \
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* OR there is a bug??? */
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FAR struct tcb_s *htcb = (FAR struct tcb_s *)pholder->htcb;
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/* Called after a semaphore has been released (incremented), the semaphore
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* could is non-negative, and there is no thread waiting for the count.
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* In this case, the priority of the holder should not be boosted.
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*/
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#if CONFIG_SEM_NNESTPRIO > 0
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DEBUGASSERT(htcb->npend_reprio == 0);
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#endif
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DEBUGASSERT(htcb->sched_priority == htcb->base_priority);
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#endif
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return 0;
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}
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#endif
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/****************************************************************************
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* Name: nxsem_dumpholder
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****************************************************************************/
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#if defined(CONFIG_DEBUG_INFO) && defined(CONFIG_SEM_PHDEBUG)
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static int nxsem_dumpholder(FAR struct semholder_s *pholder, FAR sem_t *sem,
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FAR void *arg)
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{
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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_info(" %08x: %08x %08x %04x\n",
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pholder, pholder->flink, pholder->htcb, pholder->counts);
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#else
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_info(" %08x: %08x %04x\n", pholder, pholder->htcb, pholder->counts);
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#endif
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return 0;
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}
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#endif
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/****************************************************************************
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* Name: nxsem_restoreholderprio
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****************************************************************************/
|
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static int nxsem_restoreholderprio(FAR struct tcb_s *htcb,
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FAR sem_t *sem, FAR void *arg)
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{
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FAR struct semholder_s *pholder = 0;
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#if CONFIG_SEM_NNESTPRIO > 0
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FAR struct tcb_s *stcb = (FAR struct tcb_s *)arg;
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int rpriority;
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int i;
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int j;
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#endif
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|
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/* Make sure that the holder thread is still active. If it exited without
|
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* releasing its counts, then that would be a bad thing. But we can take
|
|
* no real action because we don't know know that the program is doing.
|
|
* Perhaps its plan is to kill a thread, then destroy the semaphore.
|
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*/
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if (!sched_verifytcb(htcb))
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{
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serr("ERROR: TCB 0x%08x is a stale handle, counts lost\n", htcb);
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DEBUGPANIC();
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pholder = nxsem_findholder(sem, htcb);
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if (pholder != NULL)
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{
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nxsem_freeholder(sem, pholder);
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}
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}
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|
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/* Was the priority of the holder thread boosted? If so, then drop its
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* priority back to the correct level. What is the correct level?
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*/
|
|
|
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else if (htcb->sched_priority != htcb->base_priority)
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{
|
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#if CONFIG_SEM_NNESTPRIO > 0
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/* Are there other, pending priority levels to revert to? */
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|
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if (htcb->npend_reprio < 1)
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{
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/* No... the holder thread has only been boosted once.
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* npend_reprio should be 0 and the boosted priority should be the
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* priority of the task that just got the semaphore
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* (stcb->sched_priority)
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*
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* That latter assumption may not be true if the stcb's priority
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* was also boosted so that it no longer matches the htcb's
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* sched_priority. Or if CONFIG_SEM_NNESTPRIO is too small (so
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* that we do not have a proper record of the reprioritizations).
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*/
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DEBUGASSERT(/* htcb->sched_priority == stcb->sched_priority && */
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htcb->npend_reprio == 0);
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/* Reset the holder's priority back to the base priority. */
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sched_reprioritize(htcb, htcb->base_priority);
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}
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/* There are multiple pending priority levels. The holder thread's
|
|
* "boosted" priority could greater than or equal to
|
|
* "stcb->sched_priority" (it could be greater if its priority we
|
|
* boosted because it also holds another semaphore).
|
|
*/
|
|
|
|
else if (htcb->sched_priority <= stcb->sched_priority)
|
|
{
|
|
/* The holder thread has been boosted to the same priority as the
|
|
* waiter thread that just received the count. We will simply
|
|
* reprioritize to the next highest priority that we have in
|
|
* rpriority.
|
|
*/
|
|
|
|
/* Find the highest pending priority and remove it from the list */
|
|
|
|
for (i = 1, j = 0; i < htcb->npend_reprio; i++)
|
|
{
|
|
if (htcb->pend_reprios[i] > htcb->pend_reprios[j])
|
|
{
|
|
j = i;
|
|
}
|
|
}
|
|
|
|
/* Remove the highest priority pending priority from the list */
|
|
|
|
rpriority = htcb->pend_reprios[j];
|
|
i = htcb->npend_reprio - 1;
|
|
if (i > 0)
|
|
{
|
|
htcb->pend_reprios[j] = htcb->pend_reprios[i];
|
|
}
|
|
|
|
htcb->npend_reprio = i;
|
|
|
|
/* And apply that priority to the thread (while retaining the
|
|
* base_priority)
|
|
*/
|
|
|
|
sched_setpriority(htcb, rpriority);
|
|
}
|
|
else
|
|
{
|
|
/* The holder thread has been boosted to a higher priority than the
|
|
* waiter task. The pending priority should be in the list (unless
|
|
* it was lost because of of list overflow or because the holder
|
|
* was reprioritized again unbeknownst to the priority inheritance
|
|
* logic).
|
|
*
|
|
* Search the list for the matching priority.
|
|
*/
|
|
|
|
for (i = 0; i < htcb->npend_reprio; i++)
|
|
{
|
|
/* Does this pending priority match the priority of the thread
|
|
* that just received the count?
|
|
*/
|
|
|
|
if (htcb->pend_reprios[i] == stcb->sched_priority)
|
|
{
|
|
/* Yes, remove it from the list */
|
|
|
|
j = htcb->npend_reprio - 1;
|
|
if (j > 0)
|
|
{
|
|
htcb->pend_reprios[i] = htcb->pend_reprios[j];
|
|
}
|
|
|
|
htcb->npend_reprio = j;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
#else
|
|
/* There is no alternative restore priorities, drop the priority
|
|
* of the holder thread all the way back to the threads "base"
|
|
* priority.
|
|
*/
|
|
|
|
sched_reprioritize(htcb, htcb->base_priority);
|
|
#endif
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_restoreholderprioall
|
|
*
|
|
* Description:
|
|
* Reprioritize all holders
|
|
*
|
|
****************************************************************************/
|
|
|
|
static int nxsem_restoreholderprioall(FAR struct semholder_s *pholder,
|
|
FAR sem_t *sem, FAR void *arg)
|
|
{
|
|
return nxsem_restoreholderprio(pholder->htcb, sem, arg);
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_restoreholderprioA
|
|
*
|
|
* Description:
|
|
* Reprioritize all holders except the currently executing task
|
|
*
|
|
****************************************************************************/
|
|
|
|
static int nxsem_restoreholderprioA(FAR struct semholder_s *pholder,
|
|
FAR sem_t *sem, FAR void *arg)
|
|
{
|
|
FAR struct tcb_s *rtcb = this_task();
|
|
if (pholder->htcb != rtcb)
|
|
{
|
|
return nxsem_restoreholderprio(pholder->htcb, sem, arg);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_restoreholderprioB
|
|
*
|
|
* Description:
|
|
* Reprioritize only the currently executing task
|
|
*
|
|
****************************************************************************/
|
|
|
|
static int nxsem_restoreholderprioB(FAR struct semholder_s *pholder,
|
|
FAR sem_t *sem, FAR void *arg)
|
|
{
|
|
FAR struct tcb_s *rtcb = this_task();
|
|
|
|
if (pholder->htcb == rtcb)
|
|
{
|
|
|
|
/* The running task has given up a count on the semaphore */
|
|
|
|
#if CONFIG_SEM_PREALLOCHOLDERS == 0
|
|
/* In the case where there are only 2 holders. This step
|
|
* is necessary to insure we have space. Release the holder
|
|
* if all counts have been given up. before reprioritizing
|
|
* causes a context switch.
|
|
*/
|
|
|
|
nxsem_findandfreeholder(sem, rtcb);
|
|
#endif
|
|
(void)nxsem_restoreholderprio(rtcb, sem, arg);
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_restorebaseprio_irq
|
|
*
|
|
* Description:
|
|
* This function is called after the an interrupt handler posts a count on
|
|
* the semaphore. It will check if we need to drop the priority of any
|
|
* threads holding a count on the semaphore. Their priority could have
|
|
* been boosted while they held the count.
|
|
*
|
|
* Parameters:
|
|
* stcb - The TCB of the task that was just started (if any). If the
|
|
* post action caused a count to be given to another thread, then stcb
|
|
* is the TCB that received the count. Note, just because stcb received
|
|
* the count, it does not mean that it it is higher priority than other
|
|
* threads.
|
|
* sem - A reference to the semaphore being posted.
|
|
* - If the semaphore count is <0 then there are still threads waiting
|
|
* for a count. stcb should be non-null and will be higher priority
|
|
* than all of the other threads still waiting.
|
|
* - If it is ==0 then stcb refers to the thread that got the last count;
|
|
* no other threads are waiting.
|
|
* - If it is >0 then there should be no threads waiting for counts and
|
|
* stcb should be null.
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
* The scheduler is locked.
|
|
*
|
|
****************************************************************************/
|
|
|
|
static inline void nxsem_restorebaseprio_irq(FAR struct tcb_s *stcb,
|
|
FAR sem_t *sem)
|
|
{
|
|
/* Perform the following actions only if a new thread was given a count.
|
|
* The thread that received the count should be the highest priority
|
|
* of all threads waiting for a count from the semaphore. So in that
|
|
* case, the priority of all holder threads should be dropped to the
|
|
* next highest pending priority.
|
|
*/
|
|
|
|
if (stcb != NULL)
|
|
{
|
|
/* Drop the priority of all holder threads */
|
|
|
|
(void)nxsem_foreachholder(sem, nxsem_restoreholderprioall, stcb);
|
|
}
|
|
|
|
/* If there are no tasks waiting for available counts, then all holders
|
|
* should be at their base priority.
|
|
*/
|
|
|
|
#ifdef CONFIG_DEBUG_ASSERTIONS
|
|
else
|
|
{
|
|
(void)nxsem_foreachholder(sem, nxsem_verifyholder, NULL);
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_restorebaseprio_task
|
|
*
|
|
* Description:
|
|
* This function is called after the current running task releases a
|
|
* count on the semaphore. It will check if we need to drop the priority
|
|
* of any threads holding a count on the semaphore. Their priority could
|
|
* have been boosted while they held the count.
|
|
*
|
|
* Parameters:
|
|
* stcb - The TCB of the task that was just started (if any). If the
|
|
* post action caused a count to be given to another thread, then stcb
|
|
* is the TCB that received the count. Note, just because stcb received
|
|
* the count, it does not mean that it it is higher priority than other
|
|
* threads.
|
|
* sem - A reference to the semaphore being posted.
|
|
* - If the semaphore count is <0 then there are still threads waiting
|
|
* for a count. stcb should be non-null and will be higher priority
|
|
* than all of the other threads still waiting.
|
|
* - If it is ==0 then stcb refers to the thread that got the last count;
|
|
* no other threads are waiting.
|
|
* - If it is >0 then there should be no threads waiting for counts and
|
|
* stcb should be null.
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
* The scheduler is locked.
|
|
*
|
|
****************************************************************************/
|
|
|
|
static inline void nxsem_restorebaseprio_task(FAR struct tcb_s *stcb,
|
|
FAR sem_t *sem)
|
|
{
|
|
FAR struct tcb_s *rtcb = this_task();
|
|
|
|
/* Perform the following actions only if a new thread was given a count.
|
|
* The thread that received the count should be the highest priority
|
|
* of all threads waiting for a count from the semaphore. So in that
|
|
* case, the priority of all holder threads should be dropped to the
|
|
* next highest pending priority.
|
|
*/
|
|
|
|
if (stcb != NULL)
|
|
{
|
|
/* The currently executed thread should be the lower priority
|
|
* thread that just posted the count and caused this action.
|
|
* However, we cannot drop the priority of the currently running
|
|
* thread -- because that will cause it to be suspended.
|
|
*
|
|
* So, do this in two passes. First, reprioritizing all holders
|
|
* except for the running thread.
|
|
*/
|
|
|
|
(void)nxsem_foreachholder(sem, nxsem_restoreholderprioA, stcb);
|
|
|
|
/* Now, find an reprioritize only the ready to run task */
|
|
|
|
(void)nxsem_foreachholder(sem, nxsem_restoreholderprioB, stcb);
|
|
}
|
|
|
|
/* If there are no tasks waiting for available counts, then all holders
|
|
* should be at their base priority.
|
|
*/
|
|
|
|
#ifdef CONFIG_DEBUG_ASSERTIONS
|
|
else
|
|
{
|
|
(void)nxsem_foreachholder(sem, nxsem_verifyholder, NULL);
|
|
}
|
|
#endif
|
|
|
|
/* In any case, the currently executing task should have an entry in the
|
|
* list. Its counts were previously decremented; if it now holds no
|
|
* counts, then we need to remove it from the list of holders.
|
|
*/
|
|
|
|
nxsem_findandfreeholder(sem, rtcb);
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_initholders
|
|
*
|
|
* Description:
|
|
* Called from nxsem_initialize() to set up semaphore holder information.
|
|
*
|
|
* Parameters:
|
|
* None
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_initholders(void)
|
|
{
|
|
#if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
int i;
|
|
|
|
/* Put all of the pre-allocated holder structures into the free list */
|
|
|
|
g_freeholders = g_holderalloc;
|
|
for (i = 0; i < (CONFIG_SEM_PREALLOCHOLDERS - 1); i++)
|
|
{
|
|
g_holderalloc[i].flink = &g_holderalloc[i + 1];
|
|
}
|
|
|
|
g_holderalloc[CONFIG_SEM_PREALLOCHOLDERS - 1].flink = NULL;
|
|
#endif
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_destroyholder
|
|
*
|
|
* Description:
|
|
* Called from nxsem_destroyholder() to handle any holders of a semaphore
|
|
* when it is destroyed.
|
|
*
|
|
* Parameters:
|
|
* sem - A reference to the semaphore being destroyed
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_destroyholder(FAR sem_t *sem)
|
|
{
|
|
/* It is an error if a semaphore is destroyed while there are any holders
|
|
* (except perhaps the thread release the semaphore itself). Hmmm.. but
|
|
* we actually have to assume that the caller knows what it is doing because
|
|
* could have killed another thread that is the actual holder of the semaphore.
|
|
* We cannot make any assumptions about the state of the semaphore or the
|
|
* state of any of the holder threads.
|
|
*
|
|
* So just recover any stranded holders and hope the task knows what it is
|
|
* doing.
|
|
*/
|
|
|
|
#if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
if (sem->hhead != NULL)
|
|
{
|
|
serr("ERROR: Semaphore destroyed with holders\n");
|
|
DEBUGPANIC();
|
|
(void)nxsem_foreachholder(sem, nxsem_recoverholders, NULL);
|
|
}
|
|
|
|
#else
|
|
if (sem->holder[0].htcb != NULL || sem->holder[1].htcb != NULL)
|
|
{
|
|
serr("ERROR: Semaphore destroyed with holder\n");
|
|
DEBUGPANIC();
|
|
}
|
|
|
|
sem->holder[0].htcb = NULL;
|
|
sem->holder[1].htcb = NULL;
|
|
#endif
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_addholder_tcb
|
|
*
|
|
* Description:
|
|
* Called from nxsem_wait() when the calling thread obtains the semaphore;
|
|
* Called from sem_post() when the waiting thread obtains the semaphore.
|
|
*
|
|
* Parameters:
|
|
* htcb - TCB of the thread that just obtained the semaphore
|
|
* sem - A reference to the incremented semaphore
|
|
*
|
|
* Return Value:
|
|
* 0 (OK) or -1 (ERROR) if unsuccessful
|
|
*
|
|
* Assumptions:
|
|
* Interrupts are disabled.
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_addholder_tcb(FAR struct tcb_s *htcb, FAR sem_t *sem)
|
|
{
|
|
FAR struct semholder_s *pholder;
|
|
|
|
/* If priority inheritance is disabled for this thread, then do not add
|
|
* the holder. If there are never holders of the semaphore, the priority
|
|
* inheritance is effectively disabled.
|
|
*/
|
|
|
|
if ((sem->flags & PRIOINHERIT_FLAGS_DISABLE) == 0)
|
|
{
|
|
/* Find or allocate a container for this new holder */
|
|
|
|
pholder = nxsem_findorallocateholder(sem, htcb);
|
|
if (pholder != NULL)
|
|
{
|
|
/* Then set the holder and increment the number of counts held by this
|
|
* holder
|
|
*/
|
|
|
|
pholder->htcb = htcb;
|
|
pholder->counts++;
|
|
}
|
|
}
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_addholder
|
|
*
|
|
* Description:
|
|
* Called from nxsem_wait() when the calling thread obtains the semaphore
|
|
*
|
|
* Parameters:
|
|
* sem - A reference to the incremented semaphore
|
|
*
|
|
* Return Value:
|
|
* 0 (OK) or -1 (ERROR) if unsuccessful
|
|
*
|
|
* Assumptions:
|
|
* Interrupts are disabled.
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_addholder(FAR sem_t *sem)
|
|
{
|
|
nxsem_addholder_tcb(this_task(), sem);
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: void nxsem_boostpriority(sem_t *sem)
|
|
*
|
|
* Description:
|
|
*
|
|
*
|
|
* Parameters:
|
|
* None
|
|
*
|
|
* Return Value:
|
|
* 0 (OK) or -1 (ERROR) if unsuccessful
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_boostpriority(FAR sem_t *sem)
|
|
{
|
|
FAR struct tcb_s *rtcb = this_task();
|
|
|
|
/* Boost the priority of every thread holding counts on this semaphore
|
|
* that are lower in priority than the new thread that is waiting for a
|
|
* count.
|
|
*/
|
|
|
|
(void)nxsem_foreachholder(sem, nxsem_boostholderprio, rtcb);
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_releaseholder
|
|
*
|
|
* Description:
|
|
* Called from sem_post() after a thread releases one count on the
|
|
* semaphore.
|
|
*
|
|
* Parameters:
|
|
* sem - A reference to the semaphore being posted
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_releaseholder(FAR sem_t *sem)
|
|
{
|
|
FAR struct tcb_s *rtcb = this_task();
|
|
FAR struct semholder_s *pholder;
|
|
|
|
/* Find the container for this holder */
|
|
|
|
pholder = nxsem_findholder(sem, rtcb);
|
|
if (pholder != NULL && pholder->counts > 0)
|
|
{
|
|
/* Decrement the counts on this holder -- the holder will be freed
|
|
* later in nxsem_restorebaseprio.
|
|
*/
|
|
|
|
pholder->counts--;
|
|
}
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_restorebaseprio
|
|
*
|
|
* Description:
|
|
* This function is called after the current running task releases a
|
|
* count on the semaphore or an interrupt handler posts a new count. It
|
|
* will check if we need to drop the priority of any threads holding a
|
|
* count on the semaphore. Their priority could have been boosted while
|
|
* they held the count.
|
|
*
|
|
* Parameters:
|
|
* stcb - The TCB of the task that was just started (if any). If the
|
|
* post action caused a count to be given to another thread, then stcb
|
|
* is the TCB that received the count. Note, just because stcb received
|
|
* the count, it does not mean that it it is higher priority than other
|
|
* threads.
|
|
* sem - A reference to the semaphore being posted.
|
|
* - If the semaphore count is <0 then there are still threads waiting
|
|
* for a count. stcb should be non-null and will be higher priority
|
|
* than all of the other threads still waiting.
|
|
* - If it is ==0 then stcb refers to the thread that got the last count;
|
|
* no other threads are waiting.
|
|
* - If it is >0 then there should be no threads waiting for counts and
|
|
* stcb should be null.
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
* The scheduler is locked.
|
|
*
|
|
****************************************************************************/
|
|
|
|
void nxsem_restorebaseprio(FAR struct tcb_s *stcb, FAR sem_t *sem)
|
|
{
|
|
/* Check our assumptions */
|
|
|
|
DEBUGASSERT((sem->semcount > 0 && stcb == NULL) ||
|
|
(sem->semcount <= 0 && stcb != NULL));
|
|
|
|
/* Handler semaphore counts posed from an interrupt handler differently
|
|
* from interrupts posted from threads. The primary difference is that
|
|
* if the semaphore is posted from a thread, then the poster thread is
|
|
* a player in the priority inheritance scheme. The interrupt handler
|
|
* externally injects the new count without otherwise participating
|
|
* itself.
|
|
*/
|
|
|
|
if (up_interrupt_context())
|
|
{
|
|
nxsem_restorebaseprio_irq(stcb, sem);
|
|
}
|
|
else
|
|
{
|
|
nxsem_restorebaseprio_task(stcb, sem);
|
|
}
|
|
}
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_canceled
|
|
*
|
|
* Description:
|
|
* Called from nxsem_waitirq() after a thread that was waiting for a semaphore
|
|
* count was awakened because of a signal and the semaphore wait has been
|
|
* cancelled. This function restores the correct thread priority of each
|
|
* holder of the semaphore.
|
|
*
|
|
* Parameters:
|
|
* sem - A reference to the semaphore no longer being waited for
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
#ifndef CONFIG_DISABLE_SIGNALS
|
|
void nxsem_canceled(FAR struct tcb_s *stcb, FAR sem_t *sem)
|
|
{
|
|
/* Check our assumptions */
|
|
|
|
DEBUGASSERT(sem->semcount <= 0);
|
|
|
|
/* Adjust the priority of every holder as necessary */
|
|
|
|
(void)nxsem_foreachholder(sem, nxsem_restoreholderprioall, stcb);
|
|
}
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Name: sem_enumholders
|
|
*
|
|
* Description:
|
|
* Show information about threads currently waiting on this semaphore
|
|
*
|
|
* Parameters:
|
|
* sem - A reference to the semaphore
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
#if defined(CONFIG_DEBUG_FEATURES) && defined(CONFIG_SEM_PHDEBUG)
|
|
void sem_enumholders(FAR sem_t *sem)
|
|
{
|
|
#ifdef CONFIG_DEBUG_INFO
|
|
(void)nxsem_foreachholder(sem, nxsem_dumpholder, NULL);
|
|
#endif
|
|
}
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Name: nxsem_nfreeholders
|
|
*
|
|
* Description:
|
|
* Return the number of available holder containers. This is a good way
|
|
* to find out which threads are not calling sem_destroy.
|
|
*
|
|
* Parameters:
|
|
* sem - A reference to the semaphore
|
|
*
|
|
* Return Value:
|
|
* The number of available holder containers
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
#if defined(CONFIG_DEBUG_FEATURES) && defined(CONFIG_SEM_PHDEBUG)
|
|
int nxsem_nfreeholders(void)
|
|
{
|
|
#if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
FAR struct semholder_s *pholder;
|
|
int n;
|
|
|
|
for (pholder = g_freeholders, n = 0; pholder; pholder = pholder->flink)
|
|
{
|
|
n++;
|
|
}
|
|
|
|
return n;
|
|
#else
|
|
return 0;
|
|
#endif
|
|
}
|
|
#endif
|
|
|
|
#endif /* CONFIG_PRIORITY_INHERITANCE */
|