/****************************************************************************
* libs/libc/sched/task_cancelpt.c
*
* 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.
*
****************************************************************************/
/****************************************************************************
* Cancellation Points.
*
* Cancellation points shall occur when a thread is executing the following
* functions:
*
* accept() mq_timedsend() putpmsg() sigtimedwait()
* aio_suspend() msgrcv() pwrite() sigwait()
* clock_nanosleep() msgsnd() read() sigwaitinfo()
* close() msync() readv() sleep()
* connect() nanosleep() recv() system()
* creat() open() recvfrom() tcdrain()
* fcntl() pause() recvmsg() usleep()
* fdatasync() poll() select() wait()
* fsync() pread() sem_timedwait() waitid()
* getmsg() pselect() sem_wait() waitpid()
* getpmsg() pthread_cond_timedwait() send() write()
* lockf() pthread_cond_wait() sendmsg() writev()
* mq_receive() pthread_join() sendto()
* mq_send() pthread_testcancel() sigpause()
* mq_timedreceive() putmsg() sigsuspend()
*
* Each of the above function must call enter_cancellation_point() on entry
* in order to establish the cancellation point and
* leave_cancellation_point() on exit. These functions are described below.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
#include <nuttx/cancelpt.h>
#include <nuttx/tls.h>
#ifdef CONFIG_CANCELLATION_POINTS
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: enter_cancellation_point
*
* Description:
* Called at the beginning of the cancellation point to establish the
* cancellation point. This function does the following:
*
* 1. If deferred cancellation does not apply to this thread, nothing is
* done, otherwise, it
* 2. Sets state information in the caller's TCB and increments a nesting
* count.
* 3. If this is the outermost nesting level, it checks if there is a
* pending cancellation and, if so, calls either exit() or
* pthread_exit(), depending upon the type of the thread.
*
* Input Parameters:
* None
*
* Returned Value:
* true is returned if a cancellation is pending but cannot be performed
* now due to the nesting level.
*
****************************************************************************/
bool enter_cancellation_point(void)
{
FAR struct tls_info_s *tls = tls_get_info();
bool ret = false;
/* If cancellation is disabled on this thread or if this thread is using
* asynchronous cancellation, then do nothing.
*
* Special case: if the cpcount count is greater than zero, then we are
* nested and the above condition was certainly true at the outermost
* nesting level.
*/
if (((tls->tl_cpstate & CANCEL_FLAG_NONCANCELABLE) == 0 &&
(tls->tl_cpstate & CANCEL_FLAG_CANCEL_ASYNC) == 0) ||
tls->tl_cpcount > 0)
{
/* Check if there is a pending cancellation */
if ((tls->tl_cpstate & CANCEL_FLAG_CANCEL_PENDING) != 0)
{
/* Yes... return true (if we don't exit here) */
ret = true;
/* If there is a pending cancellation and we are at the outermost
* nesting level of cancellation function calls, then exit
* according to the type of the thread.
*/
if (tls->tl_cpcount == 0)
{
#ifndef CONFIG_DISABLE_PTHREAD
pthread_exit(PTHREAD_CANCELED);
#else
exit(EXIT_FAILURE);
#endif
}
}
/* Otherwise, indicate that we are at a cancellation point by
* incrementing the nesting level of the cancellation point
* functions.
*/
DEBUGASSERT(tls->tl_cpcount < INT16_MAX);
tls->tl_cpcount++;
}
return ret;
}
/****************************************************************************
* Name: leave_cancellation_point
*
* Description:
* Called at the end of the cancellation point. This function does the
* following:
*
* 1. If deferred cancellation does not apply to this thread, nothing is
* done, otherwise, it
* 2. Clears state information in the caller's TCB and decrements a
* nesting count.
* 3. If this is the outermost nesting level, it checks if there is a
* pending cancellation and, if so, calls either exit() or
* pthread_exit(), depending upon the type of the thread.
*
* Input Parameters:
* None
*
* Returned Value:
* None
*
****************************************************************************/
void leave_cancellation_point(void)
{
FAR struct tls_info_s *tls = tls_get_info();
/* If cancellation is disabled on this thread or if this thread is using
* asynchronous cancellation, then do nothing. Here we check only the
* nesting level: if the cpcount count is greater than zero, then the
* required condition was certainly true at the outermost nesting level.
*/
if (tls->tl_cpcount > 0)
{
/* Decrement the nesting level. If if would decrement to zero, then
* we are at the outermost nesting level and may need to do more.
*/
if (tls->tl_cpcount == 1)
{
/* We are no longer at the cancellation point */
tls->tl_cpcount = 0;
/* If there is a pending cancellation then just exit according to
* the type of the thread.
*/
if ((tls->tl_cpstate & CANCEL_FLAG_CANCEL_PENDING) != 0)
{
#ifndef CONFIG_DISABLE_PTHREAD
pthread_exit(PTHREAD_CANCELED);
#else
exit(EXIT_FAILURE);
#endif
}
}
else
{
/* We are not at the outermost nesting level. Just decrment the
* nesting level count.
*/
tls->tl_cpcount--;
}
}
}
/****************************************************************************
* Name: check_cancellation_point
*
* Description:
* Returns true if:
*
* 1. Deferred cancellation does applies to this thread,
* 2. We are within a cancellation point (i.e., the nesting level in the
* TCB is greater than zero).
*
* Input Parameters:
* None
*
* Returned Value:
* true is returned if a cancellation is pending but cannot be performed
* now due to the nesting level.
*
****************************************************************************/
bool check_cancellation_point(void)
{
FAR struct tls_info_s *tls = tls_get_info();
bool ret = false;
/* If cancellation is disabled on this thread or if this thread is using
* asynchronous cancellation, then return false.
*
* If the cpcount count is greater than zero, then we within a
* cancellation and will true if there is a pending cancellation.
*/
if (((tls->tl_cpstate & CANCEL_FLAG_NONCANCELABLE) == 0 &&
(tls->tl_cpstate & CANCEL_FLAG_CANCEL_ASYNC) == 0) ||
tls->tl_cpcount > 0)
{
/* Check if there is a pending cancellation. If so, return true. */
ret = ((tls->tl_cpstate & CANCEL_FLAG_CANCEL_PENDING) != 0);
}
return ret;
}
#endif /* CONFIG_CANCELLATION_POINTS */