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incubator-nuttx/sched/task/task_exithook.c

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/****************************************************************************
* sched/task/task_exithook.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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <assert.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/sched.h>
#include <nuttx/fs/fs.h>
#include <nuttx/mm/mm.h>
#include "sched/sched.h"
#include "group/group.h"
#include "signal/signal.h"
#include "task/task.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: nxtask_exitstatus
*
* Description:
* Report exit status when main task of a task group exits
*
****************************************************************************/
#ifdef CONFIG_SCHED_CHILD_STATUS
static inline void nxtask_exitstatus(FAR struct task_group_s *group,
int status)
{
FAR struct child_status_s *child;
/* Check if the parent task group has suppressed retention of
* child exit status information.
*/
if ((group->tg_flags & GROUP_FLAG_NOCLDWAIT) == 0)
{
/* No.. Find the exit status entry for this task in the parent TCB */
child = group_find_child(group, gettid());
if (child)
{
/* Save the exit status.. For the case of HAVE_GROUP_MEMBERS,
* the child status will be as exited until the last member
* of the task group exits.
*/
child->ch_status = status;
}
}
}
#else
# define nxtask_exitstatus(group,status)
#endif /* CONFIG_SCHED_CHILD_STATUS */
/****************************************************************************
* Name: nxtask_groupexit
*
* Description:
* Mark that the final thread of a child task group as exited.
*
****************************************************************************/
#ifdef CONFIG_SCHED_CHILD_STATUS
static inline void nxtask_groupexit(FAR struct task_group_s *group)
{
FAR struct child_status_s *child;
/* Check if the parent task group has suppressed retention of child exit
* status information.
*/
if ((group->tg_flags & GROUP_FLAG_NOCLDWAIT) == 0)
{
/* No.. Find the exit status entry for this task in the parent TCB */
child = group_find_child(group, gettid());
if (child)
{
/* Mark that all members of the child task group has exited */
child->ch_flags |= CHILD_FLAG_EXITED;
}
}
}
#else
# define nxtask_groupexit(group)
#endif /* CONFIG_SCHED_CHILD_STATUS */
/****************************************************************************
* Name: nxtask_sigchild
*
* Description:
* Send the SIGCHLD signal to the parent thread
*
****************************************************************************/
#ifdef CONFIG_SCHED_HAVE_PARENT
#ifdef HAVE_GROUP_MEMBERS
static inline void nxtask_sigchild(pid_t ppid, FAR struct tcb_s *ctcb,
int status)
{
FAR struct task_group_s *chgrp = ctcb->group;
FAR struct task_group_s *pgrp;
siginfo_t info;
DEBUGASSERT(chgrp);
/* Get the parent task group. It is possible that all of the members of
* the parent task group have exited. This would not be an error. In
* this case, the child task group has been orphaned.
*/
pgrp = group_findbypid(ppid);
if (!pgrp)
{
/* Set the task group ID to an invalid group ID. The dead parent
* task group ID could get reused some time in the future.
*/
chgrp->tg_ppid = INVALID_PROCESS_ID;
return;
}
/* Save the exit status now if this is the main thread of the task group
* that is exiting. Only the exiting main task of a task group carries
* interpretable exit Check if this is the main task that is exiting.
*/
#ifndef CONFIG_DISABLE_PTHREAD
if ((ctcb->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_PTHREAD)
#endif
{
nxtask_exitstatus(pgrp, status);
}
/* But only the final exiting thread in a task group, whatever it is,
* should generate SIGCHLD.
*/
if (chgrp->tg_nmembers == 1)
{
/* Mark that all of the threads in the task group have exited */
nxtask_groupexit(pgrp);
/* Create the siginfo structure. We don't actually know the cause.
* That is a bug. Let's just say that the child task just exited
* for now.
*/
info.si_signo = SIGCHLD;
info.si_code = CLD_EXITED;
info.si_errno = OK;
info.si_value.sival_ptr = NULL;
info.si_pid = chgrp->tg_pid;
info.si_status = status;
/* Send the signal to one thread in the group */
group_signal(pgrp, &info);
}
}
#else /* HAVE_GROUP_MEMBERS */
static inline void nxtask_sigchild(FAR struct tcb_s *ptcb,
FAR struct tcb_s *ctcb, int status)
{
siginfo_t info;
/* If task groups are not supported then we will report SIGCHLD when the
* task exits. Unfortunately, there could still be threads in the group
* that are still running.
*/
#ifndef CONFIG_DISABLE_PTHREAD
if ((ctcb->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_PTHREAD)
#endif
{
#ifdef CONFIG_SCHED_CHILD_STATUS
/* Save the exit status now of the main thread */
nxtask_exitstatus(ptcb->group, status);
#else /* CONFIG_SCHED_CHILD_STATUS */
/* Exit status is not retained. Just decrement the number of
* children from this parent.
*/
DEBUGASSERT(ptcb->group != NULL && ptcb->group->tg_nchildren > 0);
ptcb->group->tg_nchildren--;
#endif /* CONFIG_SCHED_CHILD_STATUS */
/* Create the siginfo structure. We don't actually know the cause.
* That is a bug. Let's just say that the child task just exited
* for now.
*/
info.si_signo = SIGCHLD;
info.si_code = CLD_EXITED;
info.si_errno = OK;
info.si_value.sival_ptr = NULL;
info.si_pid = ctcb->group->tg_pid;
info.si_status = status;
/* Send the signal. We need to use this internal interface so that we
* can provide the correct si_code value with the signal.
*/
nxsig_tcbdispatch(ptcb, &info);
}
}
#endif /* HAVE_GROUP_MEMBERS */
#else /* CONFIG_SCHED_HAVE_PARENT */
# define nxtask_sigchild(x,ctcb,status)
#endif /* CONFIG_SCHED_HAVE_PARENT */
/****************************************************************************
* Name: nxtask_signalparent
*
* Description:
* Send the SIGCHLD signal to the parent task group
*
****************************************************************************/
#ifdef CONFIG_SCHED_HAVE_PARENT
static inline void nxtask_signalparent(FAR struct tcb_s *ctcb, int status)
{
#ifdef HAVE_GROUP_MEMBERS
DEBUGASSERT(ctcb && ctcb->group);
/* Keep things stationary throughout the following */
sched_lock();
/* Send SIGCHLD to all members of the parent's task group */
nxtask_sigchild(ctcb->group->tg_ppid, ctcb, status);
sched_unlock();
#else
FAR struct tcb_s *ptcb;
/* Keep things stationary throughout the following */
sched_lock();
/* Get the TCB of the receiving, parent task. We do this early to
* handle multiple calls to nxtask_signalparent.
*/
ptcb = nxsched_get_tcb(ctcb->group->tg_ppid);
if (ptcb == NULL)
{
/* The parent no longer exists... bail */
sched_unlock();
return;
}
/* Send SIGCHLD to all members of the parent's task group. NOTE that the
* SIGCHLD signal is only sent once either (1) if this is the final thread
* of the task group that is exiting (HAVE_GROUP_MEMBERS) or (2) if the
* main thread of the group is exiting (!HAVE_GROUP_MEMBERS).
*/
nxtask_sigchild(ptcb, ctcb, status);
sched_unlock();
#endif
}
#else
# define nxtask_signalparent(ctcb,status)
#endif
/****************************************************************************
* Name: nxtask_exitwakeup
*
* Description:
* Wakeup any tasks waiting for this task to exit
*
****************************************************************************/
#if defined(CONFIG_SCHED_WAITPID) && !defined(CONFIG_SCHED_HAVE_PARENT)
static inline void nxtask_exitwakeup(FAR struct tcb_s *tcb, int status)
{
FAR struct task_group_s *group = tcb->group;
/* Have we already left the group? */
if (group)
{
/* Only tasks (and kernel threads) return valid status. Record the
* exit status when the task exists. The group, however, may still
* be executing.
*/
#ifndef CONFIG_DISABLE_PTHREAD
if ((tcb->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_PTHREAD)
#endif
{
/* Report the exit status. We do not nullify tg_statloc here
* because we want to prevent other tasks from registering for
* the return status. There is only one task per task group,
* there for, this logic should execute exactly once in the
* lifetime of the task group.
*
* "If more than one thread is suspended in waitpid() awaiting
* termination of the same process, exactly one thread will
* return the process status at the time of the target process
* termination."
*
* Hmmm.. what do we return to the others?
*/
if (group->tg_statloc != NULL)
{
*group->tg_statloc = status << 8;
}
}
/* Is this the last thread in the group? */
if (group->tg_nmembers == 1)
{
/* Yes.. Wakeup any tasks waiting for this task to exit */
group->tg_statloc = NULL;
group->tg_waitflags = 0;
while (group->tg_exitsem.semcount < 0)
{
/* Wake up the thread */
nxsem_post(&group->tg_exitsem);
}
}
}
}
#else
# define nxtask_exitwakeup(tcb, status)
#endif
/****************************************************************************
* Name: nxtask_flushstreams
*
* Description:
* Flush all streams when the final thread of a group exits.
*
****************************************************************************/
#ifdef CONFIG_FILE_STREAM
static inline void nxtask_flushstreams(FAR struct tcb_s *tcb)
{
FAR struct task_group_s *group = tcb->group;
/* Have we already left the group? Are we the last thread in the group? */
if (group && group->tg_nmembers == 1)
{
#ifdef CONFIG_MM_KERNEL_HEAP
lib_flushall(tcb->group->tg_streamlist);
#else
lib_flushall(&tcb->group->tg_streamlist);
#endif
}
}
#else
# define nxtask_flushstreams(tcb)
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxtask_exithook
*
* Description:
* This function implements some of the internal logic of exit() and
* task_delete(). This function performs some clean-up and other actions
* required when a task exits:
*
* - All open streams are flushed and closed.
* - All functions registered with atexit() and on_exit() are called, in
* the reverse order of their registration.
*
* When called from exit(), the tcb still resides at the head of the ready-
* to-run list. The following logic is safe because we will not be
* returning from the exit() call.
*
* When called from nxtask_terminate() we are operating on a different
* thread; on the thread that called task_delete(). In this case,
* task_delete will have already removed the tcb from the ready-to-run
* list to prevent any further action on this task.
*
* nonblocking will be set true only when we are called from
* nxtask_terminate() via _exit(). In that case, we must be careful to do
* nothing that can cause the cause the thread to block.
*
****************************************************************************/
void nxtask_exithook(FAR struct tcb_s *tcb, int status, bool nonblocking)
{
/* Under certain conditions, nxtask_exithook() can be called multiple
* times. A bit in the TCB was set the first time this function was
* called. If that bit is set, then just exit doing nothing more..
*/
if ((tcb->flags & TCB_FLAG_EXIT_PROCESSING) != 0)
{
return;
}
#ifdef CONFIG_CANCELLATION_POINTS
/* Mark the task as non-cancelable to avoid additional calls to exit()
* due to any cancellation point logic that might get kicked off by
* actions taken during exit processing.
*/
tcb->flags |= TCB_FLAG_NONCANCELABLE;
tcb->flags &= ~TCB_FLAG_CANCEL_PENDING;
tcb->cpcount = 0;
#endif
if (!nonblocking)
{
/* If this is the last thread in the group, then flush all streams
* (File descriptors will be closed when the TCB is deallocated).
*
* NOTES:
* 1. We cannot flush the buffered I/O if nonblocking is requested.
* that might cause this logic to block.
* 2. This function will only be called with non-blocking == true
* only when called through _exit(). _exit() behavior does not
* require that the streams be flushed
*/
nxtask_flushstreams(tcb);
}
/* If the task was terminated by another task, it may be in an unknown
* state. Make some feeble effort to recover the state.
*/
nxtask_recover(tcb);
/* NOTE: signal handling needs to be done in a criticl section */
#ifdef CONFIG_SMP
irqstate_t flags = enter_critical_section();
#endif
/* Send the SIGCHLD signal to the parent task group */
nxtask_signalparent(tcb, status);
/* Wakeup any tasks waiting for this task to exit */
nxtask_exitwakeup(tcb, status);
/* Leave the task group. Perhaps discarding any un-reaped child
* status (no zombies here!)
*/
group_leave(tcb);
/* Deallocate anything left in the TCB's queues */
nxsig_cleanup(tcb); /* Deallocate Signal lists */
#ifdef CONFIG_SCHED_DUMP_LEAK
if ((tcb->cmn.flags & TCB_FLAG_TTYPE_MASK) == TCB_FLAG_TTYPE_KERNEL)
{
kmm_memdump(tcb->pid);
}
else
{
umm_memdump(tcb->pid);
}
#endif
#ifdef CONFIG_SMP
leave_critical_section(flags);
#endif
/* This function can be re-entered in certain cases. Set a flag
* bit in the TCB to not that we have already completed this exit
* processing.
*/
tcb->flags |= TCB_FLAG_EXIT_PROCESSING;
}
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