incubator-nuttx/sched/semaphore/sem_recover.c

111 lines
3.9 KiB
C

/****************************************************************************
* sched/semaphore/sem_recover.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <assert.h>
#include <nuttx/irq.h>
#include <nuttx/arch.h>
#include <nuttx/sched.h>
#include "semaphore/semaphore.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsem_recover
*
* Description:
* This function is called from nxtask_recover() when a task is deleted via
* task_delete() or via pthread_cancel(). It current only checks on the
* case where a task is waiting for semaphore at the time that is was
* killed.
*
* REVISIT: A more complete implementation would release counts on all
* semaphores held by the thread. That would, however, require some
* significant extension to the semaphore data structures because given
* only the task, there is not mechanism to traverse all of the semaphores
* with counts held by the task.
*
* Input Parameters:
* tcb - The TCB of the terminated task or thread
*
* Returned Value:
* None.
*
* Assumptions:
* This function is called from task deletion logic in a safe context.
*
****************************************************************************/
void nxsem_recover(FAR struct tcb_s *tcb)
{
irqstate_t flags;
/* The task is being deleted. If it is waiting for a semaphore, then
* increment the count on the semaphores. This logic is almost identical
* to what you see in nxsem_wait_irq() except that no attempt is made to
* restart the exiting task.
*
* NOTE: In the case that the task is waiting we can assume: (1) That the
* task state is TSTATE_WAIT_SEM and (2) that the 'waitobj' in the TCB is
* non-null. If we get here via pthread_cancel() or via task_delete(),
* then the task state should be preserved; it will be altered in other
* cases but in those cases waitobj should be NULL anyway (but we do not
* enforce that here).
*/
flags = enter_critical_section();
if (tcb->task_state == TSTATE_WAIT_SEM)
{
FAR sem_t *sem = tcb->waitobj;
DEBUGASSERT(sem != NULL && atomic_load(NXSEM_COUNT(sem)) < 0);
/* Restore the correct priority of all threads that hold references
* to this semaphore.
*/
nxsem_canceled(tcb, sem);
/* And increment the count on the semaphore. This releases the count
* that was taken by sem_wait(). This count decremented the semaphore
* count to negative and caused the thread to be blocked in the first
* place.
*/
atomic_fetch_add(NXSEM_COUNT(sem), 1);
}
/* Release all semphore holders for the task */
nxsem_release_all(tcb);
leave_critical_section(flags);
}