/*****************************************************************************
* sched/sched_waitid.c
*
* Copyright (C) 2013 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 <sys/wait.h>
#include <signal.h>
#include <errno.h>
#include <nuttx/sched.h>
#include "os_internal.h"
#if defined(CONFIG_SCHED_WAITPID) && defined(CONFIG_SCHED_HAVE_PARENT)
/*****************************************************************************
* Private Functions
*****************************************************************************/
/*****************************************************************************
* Public Functions
*****************************************************************************/
/*****************************************************************************
* Name: waitid
*
* Description:
* The waitid() function suspends the calling thread until one child of
* the process containing the calling thread changes state. It records the
* current state of a child in the structure pointed to by 'info'. If a
* child process changed state prior to the call to waitid(), waitid()
* returns immediately. If more than one thread is suspended in wait() or
* waitpid() waiting termination of the same process, exactly one thread
* will return the process status at the time of the target process
* termination
*
* The idtype and id arguments are used to specify which children waitid()
* will wait for.
*
* If idtype is P_PID, waitid() will wait for the child with a process
* ID equal to (pid_t)id.
*
* If idtype is P_PGID, waitid() will wait for any child with a process
* group ID equal to (pid_t)id.
*
* If idtype is P_ALL, waitid() will wait for any children and id is
* ignored.
*
* The options argument is used to specify which state changes waitid()
* will will wait for. It is formed by OR-ing together one or more of the
* following flags:
*
* WEXITED - Wait for processes that have exited.
* WSTOPPED - Status will be returned for any child that has stopped
* upon receipt of a signal.
* WCONTINUED - Status will be returned for any child that was stopped
* and has been continued.
* WNOHANG - Return immediately if there are no children to wait for.
* WNOWAIT - Keep the process whose status is returned in 'info' in a
* waitable state. This will not affect the state of the process; the
* process may be waited for again after this call completes.
*
* The 'info' argument must point to a siginfo_t structure. If waitid()
* returns because a child process was found that satisfied the conditions
* indicated by the arguments idtype and options, then the structure pointed
* to by 'info' will be filled in by the system with the status of the
* process. The si_signo member will always be equal to SIGCHLD.
*
* Input Parameters:
* See description.
*
* Returned Value:
* If waitid() returns due to the change of state of one of its children,
* 0 is returned. Otherwise, -1 is returned and errno is set to indicate
* the error.
*
* The waitid() function will fail if:
*
* ECHILD - The calling process has no existing unwaited-for child
* processes.
* EINTR - The waitid() function was interrupted by a signal.
* EINVAL - An invalid value was specified for options, or idtype and id
* specify an invalid set of processes.
*
*****************************************************************************/
int waitid(idtype_t idtype, id_t id, siginfo_t *info, int options)
{
FAR _TCB *rtcb = (FAR _TCB *)g_readytorun.head;
sigset_t sigset;
int err;
int ret;
/* MISSING LOGIC: If WNOHANG is provided in the options, then this function
* should returned immediately. However, there is no mechanism available now
* know if the thread has child: The children remember their parents (if
* CONFIG_SCHED_HAVE_PARENT) but the parents do not remember their children.
*/
/* None of the options are supported except for WEXITED (which must be
* provided. Currently SIGCHILD always reports CLD_EXITED so we cannot
* distinguish any other events.
*/
#ifdef CONFIG_DEBUG
if (options != WEXITED)
{
set_errno(ENOSYS);
return ERROR;
}
#endif
/* Create a signal set that contains only SIGCHLD */
(void)sigemptyset(&sigset);
(void)sigaddset(&sigset, SIGCHLD);
/* Disable pre-emption so that nothing changes while the loop executes */
sched_lock();
/* Verify that this task actually has children and that the the requested
* TCB is actually a child of this task.
*/
if (rtcb->nchildren == 0)
{
err = ECHILD;
goto errout_with_errno;
}
else if (idtype == P_PID)
{
/* Get the TCB corresponding to this PID and make sure it is our child. */
FAR _TCB *ctcb = sched_gettcb((pid_t)id);
if (!ctcb || ctcb->parent != rtcb->pid)
{
err = ECHILD;
goto errout_with_errno;
}
}
/* Loop until the child that we are waiting for dies */
for (;;)
{
/* Check if the task has already died. Signals are not queued in
* NuttX. So a possibility is that the child has died and we
* missed the death of child signal (we got some other signal
* instead).
*/
if (rtcb->nchildren == 0 ||
(idtype == P_PID && (ret = kill((pid_t)id, 0)) < 0))
{
/* We know that the child task was running okay we stared,
* so we must have lost the signal. What can we do?
* Let's claim we were interrupted by a signal.
*/
err = EINTR;
goto errout_with_errno;
}
/* Wait for any death-of-child signal */
ret = sigwaitinfo(&sigset, info);
if (ret < 0)
{
goto errout;
}
/* Make there this was SIGCHLD */
if (info->si_signo == SIGCHLD)
{
/* Yes.. Are we waiting for the death of a specific child? */
if (idtype == P_PID)
{
/* Was this the death of the thread we were waiting for? */
if (info->si_pid == (pid_t)id)
{
/* Yes... return success */
break;
}
}
/* Are we waiting for any child to change state? */
else if (idtype == P_ALL)
{
/* Return success */
break;
}
/* Other ID types are not supported */
else /* if (idtype == P_PGID) */
{
set_errno(ENOSYS);
goto errout;
}
}
}
sched_unlock();
return OK;
errout_with_errno:
set_errno(err);
errout:
sched_unlock();
return ERROR;
}
#endif /* CONFIG_SCHED_WAITPID && CONFIG_SCHED_HAVE_PARENT*/
