/****************************************************************************
* sched/task/task_delete.c
*
* Copyright (C) 2007-2009, 2011-2013, 2016 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdlib.h>
#include <errno.h>
#include <nuttx/sched.h>
#include "sched/sched.h"
#include "task/task.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: task_delete
*
* Description:
* This function causes a specified task to cease to exist. Its stack and
* TCB will be deallocated. This function is the companion to task_create().
* This is the version of the function exposed to the user; it is simply
* a wrapper around the internal, task_terminate function.
*
* The logic in this function only deletes non-running tasks. If the 'pid'
* parameter refers to to the currently runing task, then processing is
* redirected to exit(). This can only happen if a task calls task_delete()
* in order to delete itself.
*
* This function obeys the semantics of pthread cancellation: task
* deletion is deferred if cancellation is disabled or if deferred
* cancellation is supported (with cancellation points enabled).
*
* Inputs:
* pid - The task ID of the task to delete. A pid of zero
* signifies the calling task.
*
* Return Value:
* OK on success; or ERROR on failure with the errno variable set
* appropriately.
*
****************************************************************************/
int task_delete(pid_t pid)
{
FAR struct tcb_s *dtcb;
FAR struct tcb_s *rtcb;
int ret;
/* Check if the task to delete is the calling task: PID=0 means to delete
* the calling task. In this case, task_delete() is much like exit()
* except that it obeys the cancellation semantics.
*/
rtcb = this_task();
if (pid == 0)
{
pid = rtcb->pid;
}
/* Get the TCB of the task to be deleted */
dtcb = (FAR struct tcb_s *)sched_gettcb(pid);
if (dtcb == NULL)
{
/* The pid does not correspond to any known thread. The task
* has probably already exited.
*/
set_errno(ESRCH);
return ERROR;
}
/* Only tasks and kernel threads should use this interface */
DEBUGASSERT((dtcb->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_PTHREAD);
/* Check to see if this task has the non-cancelable bit set in its
* flags. Suppress context changes for a bit so that the flags are stable.
* (the flags should not change in interrupt handling).
*/
sched_lock();
if ((dtcb->flags & TCB_FLAG_NONCANCELABLE) != 0)
{
/* Then we cannot cancel the thread now. Here is how this is
* supposed to work:
*
* "When cancelability is disabled, all cancels are held pending
* in the target thread until the thread changes the cancelability.
* When cancelability is deferred, all cancels are held pending in
* the target thread until the thread changes the cancelability, calls
* a function which is a cancellation point or calls pthread_testcancel(),
* thus creating a cancellation point. When cancelability is asynchronous,
* all cancels are acted upon immediately, interrupting the thread with its
* processing."
*/
dtcb->flags |= TCB_FLAG_CANCEL_PENDING;
sched_unlock();
return OK;
}
#ifdef CONFIG_CANCELLATION_POINTS
/* Check if this task supports deferred cancellation */
if ((dtcb->flags & TCB_FLAG_CANCEL_DEFERRED) != 0)
{
/* Then we cannot cancel the task asynchronously. Mark the cancellation
* as pending.
*/
dtcb->flags |= TCB_FLAG_CANCEL_PENDING;
/* If the task is waiting at a cancellation point, then notify of the
* cancellation thereby waking the task up with an ECANCELED error.
*/
if (dtcb->cpcount > 0)
{
notify_cancellation(dtcb);
}
sched_unlock();
return OK;
}
#endif
/* Check if the task to delete is the calling task */
sched_unlock();
if (pid == rtcb->pid)
{
/* If it is, then what we really wanted to do was exit. Note that we
* don't bother to unlock the TCB since it will be going away.
*/
exit(EXIT_SUCCESS);
}
/* Otherwise, perform the asynchronous cancellation, letting
* task_terminate() do all of the heavy lifting.
*/
ret = task_terminate(pid, false);
if (ret < 0)
{
set_errno(-ret);
return ERROR;
}
return OK;
}