126 lines
4.8 KiB
C
126 lines
4.8 KiB
C
/****************************************************************************
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* sched/semaphore/sem_recover.c
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*
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* Copyright (C) 2014, 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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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/sched.h>
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#include "semaphore/semaphore.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxsem_recover
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*
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* Description:
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* This function is called from task_recover() when a task is deleted via
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* task_delete() or via pthread_cancel(). It current only checks on the
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* case where a task is waiting for semaphore at the time that is was
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* killed.
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*
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* REVISIT: A more complete implementation would release counts on all
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* semaphores held by the thread. That would, however, require some
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* significant extension to the semaphore data structures because given
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* only the task, there is not mechanism to traverse all of the semaphores
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* with counts held by the task.
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*
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* Input Parameters:
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* tcb - The TCB of the terminated task or thread
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*
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* Returned Value:
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* None.
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*
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* Assumptions:
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* This function is called from task deletion logic in a safe context.
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*
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****************************************************************************/
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void nxsem_recover(FAR struct tcb_s *tcb)
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{
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irqstate_t flags;
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/* The task is being deleted. If it is waiting for a semphore, then
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* increment the count on the semaphores. This logic is almost identical
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* to what you see in nxsem_wait_irq() except that no attempt is made to
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* restart the exiting task.
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*
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* NOTE: In the case that the task is waiting we can assume: (1) That the
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* task state is TSTATE_WAIT_SEM and (2) that the 'waitsem' in the TCB is
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* non-null. If we get here via pthread_cancel() or via task_delete(),
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* then the task state should be preserved; it will be altered in other
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* cases but in those cases waitsem should be NULL anyway (but we do not
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* enforce that here).
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*/
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flags = enter_critical_section();
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if (tcb->task_state == TSTATE_WAIT_SEM)
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{
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sem_t *sem = tcb->waitsem;
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DEBUGASSERT(sem != NULL && sem->semcount < 0);
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/* Restore the correct priority of all threads that hold references
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* to this semaphore.
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*/
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nxsem_canceled(tcb, sem);
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/* And increment the count on the semaphore. This releases the count
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* that was taken by sem_wait(). This count decremented the semaphore
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* count to negative and caused the thread to be blocked in the first
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* place.
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*/
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sem->semcount++;
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/* Clear the semaphore to assure that it is not reused. But leave the
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* state as TSTATE_WAIT_SEM. This is necessary because this is a
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* necessary indication that the TCB still resides in the waiting-for-
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* semaphore list.
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*/
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tcb->waitsem = NULL;
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}
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leave_critical_section(flags);
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}
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