410 lines
13 KiB
C
410 lines
13 KiB
C
/*****************************************************************************
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* sched/sched_waitid.c
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*
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* Copyright (C) 2013 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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 <sys/wait.h>
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#include <signal.h>
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#include <errno.h>
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#include <nuttx/sched.h>
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#include "os_internal.h"
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#include "group_internal.h"
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#if defined(CONFIG_SCHED_WAITPID) && defined(CONFIG_SCHED_HAVE_PARENT)
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/*****************************************************************************
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* Private Functions
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*****************************************************************************/
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/*****************************************************************************
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* Name: exited_child
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*
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* Description:
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* Handle the case where a child exited properlay was we (apparently) lost
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* the detch of child signal.
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*
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*****************************************************************************/
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#ifdef CONFIG_SCHED_CHILD_STATUS
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static void exited_child(FAR struct tcb_s *rtcb, FAR struct child_status_s *child,
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FAR siginfo_t *info)
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{
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/* The child has exited. Return the saved exit status (and some fudged
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* information.
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*/
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info->si_signo = SIGCHLD;
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info->si_code = CLD_EXITED;
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info->si_value.sival_ptr = NULL;
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info->si_pid = child->ch_pid;
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info->si_status = child->ch_status;
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/* Discard the child entry */
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(void)group_removechild(rtcb->group, child->ch_pid);
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group_freechild(child);
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}
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#endif
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/*****************************************************************************
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* Public Functions
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*****************************************************************************/
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/*****************************************************************************
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* Name: waitid
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*
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* Description:
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* The waitid() function suspends the calling thread until one child of
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* the process containing the calling thread changes state. It records the
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* current state of a child in the structure pointed to by 'info'. If a
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* child process changed state prior to the call to waitid(), waitid()
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* returns immediately. If more than one thread is suspended in wait() or
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* waitpid() waiting termination of the same process, exactly one thread
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* will return the process status at the time of the target process
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* termination
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*
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* The idtype and id arguments are used to specify which children waitid()
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* will wait for.
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*
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* If idtype is P_PID, waitid() will wait for the child with a process
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* ID equal to (pid_t)id.
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*
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* If idtype is P_PGID, waitid() will wait for any child with a process
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* group ID equal to (pid_t)id.
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*
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* If idtype is P_ALL, waitid() will wait for any children and id is
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* ignored.
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*
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* The options argument is used to specify which state changes waitid()
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* will will wait for. It is formed by OR-ing together one or more of the
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* following flags:
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*
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* WEXITED - Wait for processes that have exited.
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* WSTOPPED - Status will be returned for any child that has stopped
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* upon receipt of a signal.
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* WCONTINUED - Status will be returned for any child that was stopped
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* and has been continued.
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* WNOHANG - Return immediately if there are no children to wait for.
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* WNOWAIT - Keep the process whose status is returned in 'info' in a
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* waitable state. This will not affect the state of the process; the
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* process may be waited for again after this call completes.
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*
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* The 'info' argument must point to a siginfo_t structure. If waitid()
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* returns because a child process was found that satisfied the conditions
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* indicated by the arguments idtype and options, then the structure pointed
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* to by 'info' will be filled in by the system with the status of the
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* process. The si_signo member will always be equal to SIGCHLD.
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*
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* Input Parameters:
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* See description.
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*
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* Returned Value:
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* If waitid() returns due to the change of state of one of its children,
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* 0 is returned. Otherwise, -1 is returned and errno is set to indicate
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* the error.
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*
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* The waitid() function will fail if:
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*
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* ECHILD - The calling process has no existing unwaited-for child
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* processes.
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* EINTR - The waitid() function was interrupted by a signal.
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* EINVAL - An invalid value was specified for options, or idtype and id
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* specify an invalid set of processes.
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*
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*****************************************************************************/
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int waitid(idtype_t idtype, id_t id, FAR siginfo_t *info, int options)
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{
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FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head;
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FAR struct tcb_s *ctcb;
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#ifdef CONFIG_SCHED_CHILD_STATUS
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FAR struct child_status_s *child;
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bool retains;
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#endif
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sigset_t sigset;
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int err;
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int ret;
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/* MISSING LOGIC: If WNOHANG is provided in the options, then this function
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* should returned immediately. However, there is no mechanism available now
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* know if the thread has child: The children remember their parents (if
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* CONFIG_SCHED_HAVE_PARENT) but the parents do not remember their children.
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*/
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/* None of the options are supported except for WEXITED (which must be
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* provided. Currently SIGCHILD always reports CLD_EXITED so we cannot
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* distinguish any other events.
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*/
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#ifdef CONFIG_DEBUG
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if (options != WEXITED)
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{
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set_errno(ENOSYS);
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return ERROR;
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}
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#endif
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/* Create a signal set that contains only SIGCHLD */
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(void)sigemptyset(&sigset);
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(void)sigaddset(&sigset, SIGCHLD);
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/* Disable pre-emption so that nothing changes while the loop executes */
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sched_lock();
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/* Verify that this task actually has children and that the requested
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* TCB is actually a child of this task.
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*/
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#ifdef CONFIG_SCHED_CHILD_STATUS
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/* Does this task retain child status? */
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retains = ((rtcb->group->tg_flags && GROUP_FLAG_NOCLDWAIT) == 0);
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if (rtcb->group->tg_children == NULL && retains)
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{
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/* There are no children */
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err = ECHILD;
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goto errout_with_errno;
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}
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else if (idtype == P_PID)
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{
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/* Get the TCB corresponding to this PID and make sure it is our child. */
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ctcb = sched_gettcb((pid_t)id);
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#ifdef HAVE_GROUP_MEMBERS
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if (!ctcb || ctcb->group->tg_pgid != rtcb->group->tg_gid)
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#else
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if (!ctcb || ctcb->ppid != rtcb->pid)
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#endif
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{
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err = ECHILD;
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goto errout_with_errno;
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}
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/* Does this task retain child status? */
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if (retains)
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{
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/* Check if this specific pid has allocated child status? */
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if (group_findchild(rtcb->group, (pid_t)id) == NULL)
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{
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/* This specific pid is not a child */
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err = ECHILD;
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goto errout_with_errno;
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}
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}
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}
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#else
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if (rtcb->nchildren == 0)
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{
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/* There are no children */
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err = ECHILD;
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goto errout_with_errno;
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}
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else if (idtype == P_PID)
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{
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/* Get the TCB corresponding to this PID and make sure it is our child. */
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ctcb = sched_gettcb((pid_t)id);
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#ifdef HAVE_GROUP_MEMBERS
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if (!ctcb || ctcb->group->tg_pgid != rtcb->group->tg_gid)
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#else
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if (!ctcb || ctcb->ppid != rtcb->pid)
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#endif
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{
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err = ECHILD;
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goto errout_with_errno;
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}
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}
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#endif
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/* Loop until the child that we are waiting for dies */
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for (;;)
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{
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#ifdef CONFIG_SCHED_CHILD_STATUS
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/* Check if the task has already died. Signals are not queued in
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* NuttX. So a possibility is that the child has died and we
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* missed the death of child signal (we got some other signal
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* instead).
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*/
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DEBUGASSERT(!retains || rtcb->group->tg_children);
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if (idtype == P_ALL)
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{
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/* We are waiting for any child to exit */
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if (retains && (child = group_exitchild(rtcb->group)) != NULL)
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{
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/* A child has exited. Apparently we missed the signal.
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* Return the exit status and break out of the loop.
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*/
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exited_child(rtcb, child, info);
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break;
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}
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}
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/* We are waiting for a specific PID. Does this task retain child status? */
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else if (retains)
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{
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/* Yes ... Get the current status of the child task. */
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child = group_findchild(rtcb->group, (pid_t)id);
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DEBUGASSERT(child);
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/* Did the child exit? */
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if ((child->ch_flags & CHILD_FLAG_EXITED) != 0)
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{
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/* The child has exited. Return the exit status and break out
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* of the loop.
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*/
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exited_child(rtcb, child, info);
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break;
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}
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}
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else
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{
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/* We can use kill() with signal number 0 to determine if that
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* task is still alive.
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*/
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ret = kill((pid_t)id, 0);
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if (ret < 0)
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{
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/* It is no longer running. We know that the child task
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* was running okay when we started, so we must have lost
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* the signal. In this case, we know that the task exit'ed,
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* but we do not know its exit status. It would be better
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* to reported ECHILD than bogus status.
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*/
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err = ECHILD;
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goto errout_with_errno;
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}
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}
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#else
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/* Check if the task has already died. Signals are not queued in
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* NuttX. So a possibility is that the child has died and we
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* missed the death of child signal (we got some other signal
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* instead).
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*/
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if (rtcb->nchildren == 0 ||
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(idtype == P_PID && (ret = kill((pid_t)id, 0)) < 0))
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{
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/* We know that the child task was running okay we stared,
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* so we must have lost the signal. What can we do?
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* Let's return ECHILD.. that is at least informative.
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*/
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err = ECHILD;
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goto errout_with_errno;
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}
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#endif
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/* Wait for any death-of-child signal */
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ret = sigwaitinfo(&sigset, info);
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if (ret < 0)
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{
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goto errout;
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}
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/* Make there this was SIGCHLD */
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if (info->si_signo == SIGCHLD)
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{
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/* Yes.. Are we waiting for the death of a specific child? */
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if (idtype == P_PID)
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{
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/* Was this the death of the thread we were waiting for? */
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if (info->si_pid == (pid_t)id)
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{
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/* Yes... return success */
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break;
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}
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}
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/* Are we waiting for any child to change state? */
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else if (idtype == P_ALL)
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{
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/* Return success */
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break;
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}
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/* Other ID types are not supported */
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else /* if (idtype == P_PGID) */
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{
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set_errno(ENOSYS);
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goto errout;
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}
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}
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}
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sched_unlock();
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return OK;
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errout_with_errno:
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set_errno(err);
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errout:
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sched_unlock();
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return ERROR;
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}
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#endif /* CONFIG_SCHED_WAITPID && CONFIG_SCHED_HAVE_PARENT */
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