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112b8cf470
The comment about the CPU index remaining stable is incorrect. There is no guarantee the task does not yield during the exit process, meaning the CPU can most definitely change. Also, there is no reason why it should not be allowed to change. This fixes a full system crash during process exit when the CPU changes and we query the current task from the old CPU.
158 lines
4.7 KiB
C
158 lines
4.7 KiB
C
/****************************************************************************
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* sched/task/task_exit.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 <debug.h>
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#include "sched/sched.h"
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#ifdef CONFIG_SMP
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# include "irq/irq.h"
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#endif
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#include "signal/signal.h"
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#include "task/task.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxtask_exit
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*
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* Description:
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* This is a part of the logic used to implement _exit(). The full
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* implementation of _exit() is architecture-dependent. The _exit()
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* function also implements the bottom half of exit() and pthread_exit().
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*
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* This function causes the currently running task (i.e., the task at the
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* head of the ready-to-run list) to cease to exist. This function should
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* never be called from normal user code, but only from the architecture-
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* specific implementation of exit.
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*
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* Threads/tasks could also be terminated via pthread_cancel,
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* task_delete(), and task_restart(). In the last two cases, the
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* task will be terminated as though exit() were called.
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* OK on success; or ERROR on failure
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*
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* Assumptions:
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* Executing within a critical section established by the caller.
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*
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****************************************************************************/
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int nxtask_exit(void)
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{
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FAR struct tcb_s *dtcb;
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FAR struct tcb_s *rtcb;
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int ret;
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#ifdef CONFIG_SMP
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/* Avoid using this_task() because it may assume a state that is not
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* appropriate for an exiting task.
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*/
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dtcb = current_task(this_cpu());
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#else
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dtcb = this_task();
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#endif
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sinfo("%s pid=%d,TCB=%p\n", get_task_name(dtcb),
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dtcb->pid, dtcb);
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/* Update scheduler parameters */
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nxsched_suspend_scheduler(dtcb);
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/* Remove the TCB of the current task from the ready-to-run list. A
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* context switch will definitely be necessary -- that must be done
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* by the architecture-specific logic.
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*
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* nxsched_remove_readytorun will mark the task at the head of the
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* ready-to-run with state == TSTATE_TASK_RUNNING
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*/
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nxsched_remove_self(dtcb);
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/* Get the new task at the head of the ready to run list */
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#ifdef CONFIG_SMP
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rtcb = current_task(this_cpu());
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#else
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rtcb = this_task();
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#endif
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/* NOTE: nxsched_resume_scheduler() was moved to up_exit()
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* because the global IRQ control for SMP should be deferred until
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* context switching, otherwise, the context switching would be done
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* without a critical section
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*/
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/* We are now in a bad state -- the head of the ready to run task list
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* does not correspond to the thread that is running. Disabling pre-
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* emption on this TCB and marking the new ready-to-run task as not
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* running.
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*
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* We disable pre-emption here by directly incrementing the lockcount
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* (vs. calling sched_lock()).
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*/
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rtcb->lockcount++;
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rtcb->task_state = TSTATE_TASK_READYTORUN;
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#ifdef CONFIG_SMP
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/* NOTE:
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* During nxtask_terminate(), enter_critical_section() will be called
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* to deallocate tcb. However, this would acquire g_cpu_irqlock if
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* rtcb->irqcount = 0, event though we are in critical section.
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* To prevent from acquiring, increment rtcb->irqcount here.
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*/
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rtcb->irqcount++;
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#endif
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dtcb->task_state = TSTATE_TASK_INACTIVE;
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ret = nxsched_release_tcb(dtcb, dtcb->flags & TCB_FLAG_TTYPE_MASK);
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#ifdef CONFIG_SMP
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rtcb->irqcount--;
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#endif
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rtcb->task_state = TSTATE_TASK_RUNNING;
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/* Decrement the lockcount on rctb. */
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rtcb->lockcount--;
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return ret;
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}
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