3e13ed2400
This caused a problem when the thread calling sem_wait() was very low priority. When it received the count, there may be higher priority threads "hogging" the CPU that prevent the lower priority task from running and, as a result, the sem_addholder() may be delayed indefinitely. The fix was to have sem_post() call sem_addholder() just before restarting the thread waiting for the semaphore count. This problem was noted by Benix Vincent who also suggested the solution.
118 lines
3.8 KiB
C
118 lines
3.8 KiB
C
/****************************************************************************
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* sched/semaphore/semaphore.h
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*
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* Copyright (C) 2007, 2009-2016 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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#ifndef __SCHED_SEMAPHORE_SEMAPHORE_H
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#define __SCHED_SEMAPHORE_SEMAPHORE_H
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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 <nuttx/compiler.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <semaphore.h>
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#include <sched.h>
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#include <queue.h>
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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#ifdef __cplusplus
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#define EXTERN extern "C"
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extern "C"
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{
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#else
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#define EXTERN extern
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#endif
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/* Common semaphore logic */
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#ifdef CONFIG_PRIORITY_INHERITANCE
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void sem_initialize(void);
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#else
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# define sem_initialize()
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#endif
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/* Wake up a thread that is waiting on semaphore */
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void sem_waitirq(FAR struct tcb_s *wtcb, int errcode);
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/* Handle semaphore timer expiration */
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void sem_timeout(int argc, wdparm_t pid);
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/* Recover semaphore resources with a task or thread is destroyed */
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void sem_recover(FAR struct tcb_s *tcb);
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/* Special logic needed only by priority inheritance to manage collections of
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* holders of semaphores.
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*/
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#ifdef CONFIG_PRIORITY_INHERITANCE
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void sem_initholders(void);
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void sem_destroyholder(FAR sem_t *sem);
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void sem_addholder(FAR sem_t *sem);
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void sem_addholder_tcb(FAR struct tcb_s *htcb, FAR sem_t *sem);
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void sem_boostpriority(FAR sem_t *sem);
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void sem_releaseholder(FAR sem_t *sem);
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void sem_restorebaseprio(FAR struct tcb_s *stcb, FAR sem_t *sem);
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# ifndef CONFIG_DISABLE_SIGNALS
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void sem_canceled(FAR struct tcb_s *stcb, FAR sem_t *sem);
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# else
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# define sem_canceled(stcb, sem)
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# endif
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#else
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# define sem_initholders()
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# define sem_destroyholder(sem)
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# define sem_addholder(sem)
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# define sem_addholder_tcb(htcb,sem)
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# define sem_boostpriority(sem)
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# define sem_releaseholder(sem)
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# define sem_restorebaseprio(stcb,sem)
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# define sem_canceled(stcb,sem)
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#endif
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#undef EXTERN
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#ifdef __cplusplus
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}
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#endif
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#endif /* __SCHED_SEMAPHORE_SEMAPHORE_H */
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