367beee228
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1591 42af7a65-404d-4744-a932-0658087f49c3
479 lines
14 KiB
C
479 lines
14 KiB
C
/****************************************************************************
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* sched/sem_holder.c
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*
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* Copyright (C) 2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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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 <sys/types.h>
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#include <semaphore.h>
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#include <sched.h>
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#include <debug.h>
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#include <nuttx/arch.h>
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#include "os_internal.h"
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#include "sem_internal.h"
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/****************************************************************************
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* 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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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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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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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Function: sem_allocholder
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****************************************************************************/
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static inline FAR struct semholder_s *sem_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 (!sem->hlist.holder)
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{
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pholder = &sem->hlist;
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}
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else
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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)
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{
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/* Remove the holder from the free list an put it into the semaphore's holder list */
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g_freeholders = pholder->flink;
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pholder->flink = sem->hlist.flink;
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sem->hlist.flink = pholder;
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/* Make sure the 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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#else
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pholder = NULL;
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#endif
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sdbg("Insufficient pre-allocated holders\n");
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}
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return pholder;
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}
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/****************************************************************************
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* Function: sem_findholder
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****************************************************************************/
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static FAR struct semholder_s *sem_findholder(sem_t *sem, FAR _TCB *htcb)
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{
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FAR struct semholder_s *pholder;
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/* Try to find the holder in the list of holders associated with this semaphore */
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pholder = &sem->hlist;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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for (; pholder; pholder = pholder->flink)
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#endif
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{
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if (pholder->holder == 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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/* 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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* Function: sem_findorallocateholder
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****************************************************************************/
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static inline FAR struct semholder_s *sem_findorallocateholder(sem_t *sem, FAR _TCB *htcb)
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{
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FAR struct semholder_s *pholder = sem_findholder(sem, htcb);
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if (!pholder)
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{
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pholder = sem_allocholder(sem);
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}
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return pholder;
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}
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/****************************************************************************
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* Function: sem_freeholder
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****************************************************************************/
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static inline void sem_freeholder(sem_t *sem, 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->holder = 0;
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pholder->counts = 0;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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/* If this is the holder inside the semaphore, then do nothing more */
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if (pholder != &sem->hlist)
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{
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/* Otherwise, search the list for the matching holder */
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for (prev = &sem->hlist, curr = sem->hlist.flink;
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curr && curr != pholder;
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prev = curr, curr = curr->flink);
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if (curr)
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{
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/* Remove the holder from the list */
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prev->flink = pholder->flink;
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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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}
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#endif
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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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* Function: sem_initholders
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*
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* Description:
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* Called from sem_initialize() to set up semaphore holder information.
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*
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* Parameters:
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* None
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*
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* Return Value:
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* None
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_initholders(void)
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{
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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int i;
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/* Put all of the pre-allocated holder structures into free list */
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g_freeholders = g_holderalloc;
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for (i = 0; i < (CONFIG_SEM_PREALLOCHOLDERS-1); i++)
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{
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g_holderalloc[i].flink = &g_holderalloc[i+1];
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}
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g_holderalloc[CONFIG_SEM_PREALLOCHOLDERS-1].flink = NULL;
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#endif
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}
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/****************************************************************************
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* Function: sem_destroyholder
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*
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* Description:
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* Called from sem_destroy() to handle any holders of a semaphore when
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* it is destroyed.
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*
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* Parameters:
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* sem - A reference to the semaphore being destroyed
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*
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* Return Value:
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* None
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_destroyholder(sem_t *sem)
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{
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#if 0
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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/* It is an error is a semaphore is destroyed while there are any holders
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* (except perhaps the thread releas the semaphore itself). Hmmm.. but
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* we actually have to assume that the caller knows what it is doing because
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* could have killed another thread that is the actual holder of the semaphore.
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*/
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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DEBUGASSERT((!sem->hlist.holder || sem->hlist.holder == rtcb) && !sem->hlist.flink);
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#else
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DEBUGASSERT(!sem->hlist.holder || sem->hlist.holder == rtcb);
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#endif
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#endif
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sem->hlist.holder = NULL;
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}
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/****************************************************************************
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* Function: sem_addholder
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*
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* Description:
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* Called from sem_wait() when the calling thread obtains the semaphore
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*
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* Parameters:
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* sem - A reference to the incremented semaphore
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*
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* Return Value:
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* 0 (OK) or -1 (ERROR) if unsuccessful
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_addholder(sem_t *sem)
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{
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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FAR struct semholder_s *pholder;
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/* Find or allocate a container for this new holder */
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pholder = sem_findorallocateholder(sem, rtcb);
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if (pholder)
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{
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/* Then set the holder and increment the number of counts held by this holder */
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pholder->holder = rtcb;
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pholder->counts++;
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}
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}
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/****************************************************************************
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* Function: void sem_boostpriority(sem_t *sem)
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*
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* Description:
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*
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*
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* Parameters:
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* None
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*
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* Return Value:
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* 0 (OK) or -1 (ERROR) if unsuccessful
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_boostpriority(sem_t *sem)
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{
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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FAR _TCB *htcb;
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struct semholder_s *pholder;
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/* Traverse the list of holders */
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pholder = &sem->hlist;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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for (; pholder; pholder = pholder->flink)
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#endif
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{
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/* As an artifact, there will be holders that have no counts. This
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* because they have posted the semaphore and there count was decrement
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* by sem_releaseholder(), but they are still being retained in the
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* list to be harvested by sem_restorebaseprio.
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*/
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if (pholder->counts > 0)
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{
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htcb = pholder->holder;
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#if CONFIG_SEM_NNESTPRIO > 0
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# error "Missing implementation"
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#else
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if (htcb && htcb->sched_priority < rtcb->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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#endif
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}
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}
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}
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}
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/****************************************************************************
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* Function: sem_releaseholder
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*
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* Description:
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* Called from sem_post() after a thread releases one count on the
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* semaphore.
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*
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* Parameters:
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* sem - A reference to the semaphore being posted
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*
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* Return Value:
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* None
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_releaseholder(sem_t *sem)
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{
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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FAR struct semholder_s *pholder;
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/* Find the container for this holder */
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pholder = sem_findholder(sem, rtcb);
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if (pholder && pholder->counts > 0)
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{
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/* Decrement the counts on this holder */
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pholder->counts--;
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}
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}
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/****************************************************************************
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* Function: sem_restorebaseprio
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*
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* Description:
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* Check if we need to drop the priority of any threads holding the
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* semaphore. The priority could have been boosted while they held the
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* semaphore.
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*
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* Parameters:
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* sem - A reference to the semaphore being posted
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*
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* Return Value:
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* 0 (OK) or -1 (ERROR) if unsuccessful
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_restorebaseprio(sem_t *sem)
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{
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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FAR _TCB *htcb;
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struct semholder_s *pholder;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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struct semholder_s *next;
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#endif
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/* Check if the semaphore is still available */
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if (sem->semcount > 0)
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{
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/* Traverse the list of holders */
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pholder = &sem->hlist;
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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for (; pholder; pholder = next)
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#endif
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{
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#if CONFIG_SEM_PREALLOCHOLDERS > 0
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next = pholder->flink; /* In case pholder gets deleted */
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#endif
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/* The initial "built-in" container may hold a NULL holder */
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htcb = pholder->holder;
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if (htcb)
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{
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#if CONFIG_SEM_NNESTPRIO > 0
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# error "Missing implementation"
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#else
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/* Was the priority of this thread boosted? NOTE: There is
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* a logical flaw here: If the thread holds multiple semaphore
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* and has been boosted multiple times, then there is no mechanism
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* to know the correct priority to restore and we may error in
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* prematurely lowering the priority.
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*/
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if (htcb->sched_priority != htcb->base_priority)
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{
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up_reprioritize_rtr(rtcb, htcb->base_priority);
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}
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#endif
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/* When no more counts are held, remove the holder from the list */
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if (pholder->counts <= 0)
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{
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sem_freeholder(sem, pholder);
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}
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}
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}
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}
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}
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#endif /* CONFIG_PRIORITY_INHERITANCE */
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