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3e29996d97
Change every occurence of up_switch_context to use this_task() as the first parameter. "nxsched_add_readytorun" returns "true" if context switch is required. "nxsched_add_readytorun" typically could only switch the assigned/running task to the one which is passed in as parameter. But this is not strictly guaranteed in SMP; if other CPUs tweak with affinities or priorities, it may be possible that the running task after the call is changed, but is some other task from the readytorun list (and it should be, if there is higher priority one available or the affinity of the added task prevents it to be scheduled in, but the previous head of the readytorun list should run. this_task() is always the correct one to switch to, since it always points to the tcb which was just switched in by the nxsched_add_readytorun. This is also a precursor to re-writing the SMP queue logic to remove pending lists for SMP. Signed-off-by: Jukka Laitinen <jukka.laitinen@tii.ae>
130 lines
4 KiB
C
130 lines
4 KiB
C
/****************************************************************************
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* sched/semaphore/sem_waitirq.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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 <sched.h>
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#include <assert.h>
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#include <errno.h>
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#include <nuttx/irq.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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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxsem_wait_irq
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*
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* Description:
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* This function is called when either:
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*
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* 1. A signal is received by a task that is waiting on a semaphore.
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* According to the POSIX spec, "...the calling thread shall not return
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* from the call to [nxsem_wait] until it either locks the semaphore or
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* the call is interrupted by a signal."
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* 2. From logic associated with sem_timedwait(). This function is called
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* when the timeout elapses without receiving the semaphore.
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*
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* Note: this function should be used within critical_section.
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*
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* Input Parameters:
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* wtcb - A pointer to the TCB of the task that is waiting on a
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* semphaphore, but has received a signal or timeout instead.
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* errcode - EINTR if the semaphore wait was awakened by a signal;
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* ETIMEDOUT if awakened by a timeout.
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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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*
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****************************************************************************/
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void nxsem_wait_irq(FAR struct tcb_s *wtcb, int errcode)
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{
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FAR struct tcb_s *rtcb = this_task();
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FAR sem_t *sem = wtcb->waitobj;
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bool mutex = NXSEM_IS_MUTEX(sem);
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/* It is possible that an interrupt/context switch beat us to the punch
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* and already changed the task's state.
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*/
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DEBUGASSERT(sem != NULL);
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DEBUGASSERT(mutex || atomic_read(NXSEM_COUNT(sem)) < 0);
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DEBUGASSERT(!mutex || NXSEM_MBLOCKING(atomic_read(NXSEM_MHOLDER(sem))));
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/* Mutex is never interrupted by a signal or canceled */
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if (mutex && (errcode == EINTR || errcode == ECANCELED))
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{
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return;
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}
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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(wtcb, sem);
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/* Remove task from waiting list */
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dq_rem((FAR dq_entry_t *)wtcb, SEM_WAITLIST(sem));
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/* This restores the value to what it was before the previous sem_wait.
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* This caused the thread to be blocked in the first place.
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*
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* For mutexes, the holder is updated by the thread itself
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* when it exits nxsem_wait
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*/
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if (!mutex)
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{
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atomic_fetch_add(NXSEM_COUNT(sem), 1);
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}
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/* Indicate that the wait is over. */
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wtcb->waitobj = NULL;
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/* Mark the errno value for the thread. */
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wtcb->errcode = errcode;
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/* Add the task to ready-to-run task list and
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* perform the context switch if one is needed
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*/
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if (nxsched_add_readytorun(wtcb))
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{
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up_switch_context(this_task(), rtcb);
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}
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}
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