416 lines
13 KiB
C
416 lines
13 KiB
C
/****************************************************************************
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* sched/task/task_cancelpt.c
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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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* Cancellation Points.
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*
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* Cancellation points shall occur when a thread is executing the following
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* functions:
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*
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* accept() mq_timedsend() putpmsg() sigtimedwait()
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* aio_suspend() msgrcv() pwrite() sigwait()
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* clock_nanosleep() msgsnd() read() sigwaitinfo()
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* close() msync() readv() sleep()
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* connect() nanosleep() recv() system()
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* creat() open() recvfrom() tcdrain()
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* fcntl() pause() recvmsg() usleep()
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* fdatasync() poll() select() wait()
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* fsync() pread() sem_timedwait() waitid()
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* getmsg() pselect() sem_wait() waitpid()
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* getpmsg() pthread_cond_timedwait() send() write()
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* lockf() pthread_cond_wait() sendmsg() writev()
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* mq_receive() pthread_join() sendto()
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* mq_send() pthread_testcancel() sigpause()
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* mq_timedreceive() putmsg() sigsuspend()
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*
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* Each of the above function must call enter_cancellation_point() on entry
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* in order to establish the cancellation point and
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* leave_cancellation_point() on exit. These functions are described below.
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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/cancelpt.h>
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#include "sched/sched.h"
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#include "semaphore/semaphore.h"
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#include "signal/signal.h"
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#include "mqueue/mqueue.h"
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#include "task/task.h"
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#ifdef CONFIG_CANCELLATION_POINTS
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: enter_cancellation_point
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*
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* Description:
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* Called at the beginning of the cancellation point to establish the
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* cancellation point. This function does the following:
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*
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* 1. If deferred cancellation does not apply to this thread, nothing is
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* done, otherwise, it
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* 2. Sets state information in the caller's TCB and increments a nesting
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* count.
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* 3. If this is the outermost nesting level, it checks if there is a
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* pending cancellation and, if so, calls either exit() or
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* pthread_exit(), depending upon the type of the thread.
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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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* true is returned if a cancellation is pending but cannot be performed
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* now due to the nesting level.
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*
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****************************************************************************/
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bool enter_cancellation_point(void)
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{
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FAR struct tcb_s *tcb = this_task();
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bool ret = false;
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/* Disabling pre-emption should provide sufficient protection. We only
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* need the TCB to be stationary (no interrupt level modification is
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* anticipated).
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*
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* REVISIT: is locking the scheduler sufficient in SMP mode?
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*/
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sched_lock();
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/* If cancellation is disabled on this thread or if this thread is using
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* asynchronous cancellation, then do nothing.
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*
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* Special case: if the cpcount count is greater than zero, then we are
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* nested and the above condition was certainly true at the outermost
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* nesting level.
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*/
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if (((tcb->flags & TCB_FLAG_NONCANCELABLE) == 0 &&
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(tcb->flags & TCB_FLAG_CANCEL_DEFERRED) != 0) ||
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tcb->cpcount > 0)
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{
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/* Check if there is a pending cancellation */
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if ((tcb->flags & TCB_FLAG_CANCEL_PENDING) != 0)
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{
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/* Yes... return true (if we don't exit here) */
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ret = true;
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/* If there is a pending cancellation and we are at the outermost
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* nesting level of cancellation function calls, then exit
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* according to the type of the thread.
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*/
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if (tcb->cpcount == 0)
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{
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#ifndef CONFIG_DISABLE_PTHREAD
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if ((tcb->flags & TCB_FLAG_TTYPE_MASK) ==
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TCB_FLAG_TTYPE_PTHREAD)
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{
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pthread_exit(PTHREAD_CANCELED);
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}
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else
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#endif
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{
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exit(EXIT_FAILURE);
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}
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}
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}
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/* Otherwise, indicate that we are at a cancellation point by
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* incrementing the nesting level of the cancellation point
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* functions.
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*/
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DEBUGASSERT(tcb->cpcount < INT16_MAX);
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tcb->cpcount++;
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}
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sched_unlock();
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return ret;
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}
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/****************************************************************************
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* Name: leave_cancellation_point
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*
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* Description:
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* Called at the end of the cancellation point. This function does the
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* following:
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*
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* 1. If deferred cancellation does not apply to this thread, nothing is
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* done, otherwise, it
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* 2. Clears state information in the caller's TCB and decrements a
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* nesting count.
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* 3. If this is the outermost nesting level, it checks if there is a
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* pending cancellation and, if so, calls either exit() or
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* pthread_exit(), depending upon the type of the thread.
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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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* None
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*
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****************************************************************************/
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void leave_cancellation_point(void)
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{
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FAR struct tcb_s *tcb = this_task();
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/* Disabling pre-emption should provide sufficient protection. We only
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* need the TCB to be stationary (no interrupt level modification is
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* anticipated).
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*
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* REVISIT: is locking the scheduler sufficient in SMP mode?
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*/
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sched_lock();
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/* If cancellation is disabled on this thread or if this thread is using
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* asynchronous cancellation, then do nothing. Here we check only the
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* nesting level: if the cpcount count is greater than zero, then the
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* required condition was certainly true at the outermost nesting level.
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*/
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if (tcb->cpcount > 0)
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{
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/* Decrement the nesting level. If if would decrement to zero, then
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* we are at the outermost nesting level and may need to do more.
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*/
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if (tcb->cpcount == 1)
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{
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/* We are no longer at the cancellation point */
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tcb->cpcount = 0;
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/* If there is a pending cancellation then just exit according to
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* the type of the thread.
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*/
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if ((tcb->flags & TCB_FLAG_CANCEL_PENDING) != 0)
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{
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#ifndef CONFIG_DISABLE_PTHREAD
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if ((tcb->flags & TCB_FLAG_TTYPE_MASK) ==
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TCB_FLAG_TTYPE_PTHREAD)
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{
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pthread_exit(PTHREAD_CANCELED);
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}
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else
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#endif
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{
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exit(EXIT_FAILURE);
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}
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}
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}
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else
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{
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/* We are not at the outermost nesting level. Just decrment the
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* nesting level count.
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*/
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tcb->cpcount--;
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}
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}
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sched_unlock();
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}
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/****************************************************************************
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* Name: check_cancellation_point
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*
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* Description:
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* Returns true if:
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*
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* 1. Deferred cancellation does applies to this thread,
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* 2. We are within a cancellation point (i.e., the nesting level in the
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* TCB is greater than zero).
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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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* true is returned if a cancellation is pending but cannot be performed
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* now due to the nesting level.
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*
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****************************************************************************/
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bool check_cancellation_point(void)
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{
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FAR struct tcb_s *tcb = this_task();
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bool ret = false;
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/* Disabling pre-emption should provide sufficient protection. We only
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* need the TCB to be stationary (no interrupt level modification is
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* anticipated).
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*
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* REVISIT: is locking the scheduler sufficient in SMP mode?
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*/
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sched_lock();
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/* If cancellation is disabled on this thread or if this thread is using
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* asynchronous cancellation, then return false.
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*
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* If the cpcount count is greater than zero, then we within a
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* cancellation and will true if there is a pending cancellation.
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*/
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if (((tcb->flags & TCB_FLAG_NONCANCELABLE) == 0 &&
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(tcb->flags & TCB_FLAG_CANCEL_DEFERRED) != 0) ||
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tcb->cpcount > 0)
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{
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/* Check if there is a pending cancellation. If so, return true. */
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ret = ((tcb->flags & TCB_FLAG_CANCEL_PENDING) != 0);
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}
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sched_unlock();
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return ret;
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}
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#endif /* CONFIG_CANCELLATION_POINTS */
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/****************************************************************************
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* Name: nxnotify_cancellation
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*
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* Description:
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* Called by task_delete() or pthread_cancel() if the cancellation occurs
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* while we the thread is within the cancellation point. This logic
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* behaves much like sending a signal: It will cause waiting threads
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* to wake up and terminated with ECANCELED. A call to
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* leave_cancellation_point() would then follow, causing the thread to
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* exit.
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*
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* Returned Value:
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* Indicate whether the notification delivery to the target
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*
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****************************************************************************/
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bool nxnotify_cancellation(FAR struct tcb_s *tcb)
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{
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irqstate_t flags;
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/* We need perform the following operations from within a critical section
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* because it can compete with interrupt level activity.
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*/
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flags = enter_critical_section();
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/* We only notify the cancellation if (1) the thread has not disabled
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* cancellation, (2) the thread uses the deferred cancellation mode,
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* (3) the thread is waiting within a cancellation point.
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*/
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/* Check to see if this task has the non-cancelable bit set. */
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if ((tcb->flags & TCB_FLAG_NONCANCELABLE) != 0)
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{
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/* Then we cannot cancel the thread now. Here is how this is
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* supposed to work:
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*
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* "When cancellability is disabled, all cancels are held pending
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* in the target thread until the thread changes the cancellability.
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* When cancellability is deferred, all cancels are held pending in
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* the target thread until the thread changes the cancellability,
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* calls a function which is a cancellation point or calls
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* pthread_testcancel(), thus creating a cancellation point. When
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* cancellability is asynchronous, all cancels are acted upon
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* immediately, interrupting the thread with its processing."
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*/
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tcb->flags |= TCB_FLAG_CANCEL_PENDING;
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leave_critical_section(flags);
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return true;
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}
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#ifdef CONFIG_CANCELLATION_POINTS
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/* Check if this task supports deferred cancellation */
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if ((tcb->flags & TCB_FLAG_CANCEL_DEFERRED) != 0)
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{
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/* Then we cannot cancel the task asynchronously.
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* Mark the cancellation as pending.
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*/
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tcb->flags |= TCB_FLAG_CANCEL_PENDING;
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/* If the task is waiting at a cancellation point, then notify of the
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* cancellation thereby waking the task up with an ECANCELED error.
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*/
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if (tcb->cpcount > 0)
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{
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/* If the thread is blocked waiting for a semaphore, then the
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* thread must be unblocked to handle the cancellation.
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*/
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if (tcb->task_state == TSTATE_WAIT_SEM)
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{
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nxsem_wait_irq(tcb, ECANCELED);
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}
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/* If the thread is blocked waiting on a signal, then the
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* thread must be unblocked to handle the cancellation.
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*/
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else if (tcb->task_state == TSTATE_WAIT_SIG)
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{
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nxsig_wait_irq(tcb, ECANCELED);
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}
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#ifndef CONFIG_DISABLE_MQUEUE
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/* If the thread is blocked waiting on a message queue, then
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* the thread must be unblocked to handle the cancellation.
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*/
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else if (tcb->task_state == TSTATE_WAIT_MQNOTEMPTY ||
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tcb->task_state == TSTATE_WAIT_MQNOTFULL)
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{
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nxmq_wait_irq(tcb, ECANCELED);
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}
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#endif
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}
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leave_critical_section(flags);
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return true;
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}
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#endif
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leave_critical_section(flags);
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return false;
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}
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