249 lines
10 KiB
C
249 lines
10 KiB
C
/*****************************************************************************
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* sched/sched_waitpid.c
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*
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* Copyright (C) 2011-2012 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 <semaphore.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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#ifdef CONFIG_SCHED_WAITPID /* Experimental */
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/*****************************************************************************
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* Private Functions
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*****************************************************************************/
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/*****************************************************************************
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* Public Functions
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*****************************************************************************/
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/*****************************************************************************
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* Name: sched_waitpid
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*
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* Description:
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*
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* The waitpid() functions will obtain status information pertaining to one
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* of the caller's child processes. The waitpid() function will suspend
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* execution of the calling thread until status information for one of the
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* terminated child processes of the calling process is available, or until
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* delivery of a signal whose action is either to execute a signal-catching
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* function or to terminate the process. If more than one thread is suspended
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* in waitpid() awaiting 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. If status information is available prior to the call to
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* waitpid(), return will be immediate.
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*
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* The pid argument specifies a set of child processes for which status is
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* requested. The waitpid() function will only return the status of a child
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* process from this set:
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*
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* - If pid is equal to (pid_t)-1, status is requested for any child process.
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* In this respect, waitpid() is then equivalent to wait().
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* - If pid is greater than 0, it specifies the process ID of a single child
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* process for which status is requested.
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* - If pid is 0, status is requested for any child process whose process
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* group ID is equal to that of the calling process.
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* - If pid is less than (pid_t)-1, status is requested for any child process
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* whose process group ID is equal to the absolute value of pid.
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*
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* The options argument is constructed from the bitwise-inclusive OR of zero
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* or more of the following flags, defined in the <sys/wait.h> header:
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*
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* WCONTINUED - The waitpid() function will report the status of any
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* continued child process specified by pid whose status has not been
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* reported since it continued from a job control stop.
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* WNOHANG - The waitpid() function will not suspend execution of the
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* calling thread if status is not immediately available for one of the
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* child processes specified by pid.
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* WUNTRACED - The status of any child processes specified by pid that are
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* stopped, and whose status has not yet been reported since they stopped,
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* will also be reported to the requesting process.
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*
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* If the calling process has SA_NOCLDWAIT set or has SIGCHLD set to
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* SIG_IGN, and the process has no unwaited-for children that were
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* transformed into zombie processes, the calling thread will block until all
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* of the children of the process containing the calling thread terminate, and
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* waitpid() will fail and set errno to ECHILD.
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*
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* If waitpid() returns because the status of a child process is available,
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* these functions will return a value equal to the process ID of the child
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* process. In this case, if the value of the argument stat_loc is not a
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* null pointer, information will be stored in the location pointed to by
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* stat_loc. The value stored at the location pointed to by stat_loc will be
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* 0 if and only if the status returned is from a terminated child process
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* that terminated by one of the following means:
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*
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* 1. The process returned 0 from main().
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* 2. The process called _exit() or exit() with a status argument of 0.
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* 3. The process was terminated because the last thread in the process terminated.
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*
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* Regardless of its value, this information may be interpreted using the
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* following macros, which are defined in <sys/wait.h> and evaluate to
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* integral expressions; the stat_val argument is the integer value pointed
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* to by stat_loc.
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*
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* WIFEXITED(stat_val) - Evaluates to a non-zero value if status was
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* returned for a child process that terminated normally.
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* WEXITSTATUS(stat_val) - If the value of WIFEXITED(stat_val) is non-zero,
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* this macro evaluates to the low-order 8 bits of the status argument
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* that the child process passed to _exit() or exit(), or the value the
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* child process returned from main().
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* WIFSIGNALED(stat_val) - Evaluates to a non-zero value if status was
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* returned for a child process that terminated due to the receipt of a
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* signal that was not caught (see <signal.h>).
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* WTERMSIG(stat_val) - If the value of WIFSIGNALED(stat_val) is non-zero,
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* this macro evaluates to the number of the signal that caused the
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* termination of the child process.
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* WIFSTOPPED(stat_val) - Evaluates to a non-zero value if status was
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* returned for a child process that is currently stopped.
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* WSTOPSIG(stat_val) - If the value of WIFSTOPPED(stat_val) is non-zero,
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* this macro evaluates to the number of the signal that caused the child
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* process to stop.
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* WIFCONTINUED(stat_val) - Evaluates to a non-zero value if status was
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* returned for a child process that has continued from a job control stop.
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*
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* Parameters:
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* pid - The task ID of the thread to waid for
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* stat_loc - The location to return the exit status
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* options - ignored
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*
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* Return Value:
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* If waitpid() returns because the status of a child process is available,
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* it will return a value equal to the process ID of the child process for
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* which status is reported.
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*
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* If waitpid() returns due to the delivery of a signal to the calling
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* process, -1 will be returned and errno set to EINTR.
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*
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* If waitpid() was invoked with WNOHANG set in options, it has at least
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* one child process specified by pid for which status is not available, and
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* status is not available for any process specified by pid, 0 is returned.
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*
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* Otherwise, (pid_t)-1 will be returned, and errno set to indicate the error:
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*
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* ECHILD - The process specified by pid does not exist or is not a child of
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* the calling process, or the process group specified by pid does not exist
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* or does not have any member process that is a child of the calling process.
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* EINTR - The function was interrupted by a signal. The value of the location
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* pointed to by stat_loc is undefined.
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* EINVAL - The options argument is not valid.
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*
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* Assumptions:
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*
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*****************************************************************************/
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/***************************************************************************/
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/* NOTE: This is a partially functional, experimental version of waitpid() */
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/***************************************************************************/
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pid_t waitpid(pid_t pid, int *stat_loc, int options)
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{
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_TCB *tcb;
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bool mystat;
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int err;
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int ret;
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/* Disable pre-emption so that nothing changes in the following tests */
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sched_lock();
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tcb = sched_gettcb(pid);
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if (!tcb)
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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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/* None of the options are supported */
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#ifdef CONFIG_DEBUG
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if (options != 0)
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{
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err = ENOSYS;
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goto errout_with_errno;
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}
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#endif
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/* "If more than one thread is suspended in waitpid() awaiting termination of
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* the same process, exactly one thread will return the process status at the
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* time of the target process termination." Hmmm.. what do we return to the
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* others?
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*/
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if (stat_loc != NULL && tcb->stat_loc == NULL)
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{
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tcb->stat_loc = stat_loc;
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mystat = true;
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}
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/* Then wait for the task to exit */
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ret = sem_wait(&tcb->exitsem);
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if (ret < 0)
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{
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/* Unlock pre-emption and return the ERROR (sem_wait has already set
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* the errno). Handle the awkward case of whether or not we need to
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* nullify the stat_loc value.
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*/
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if (mystat)
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{
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tcb->stat_loc = NULL;
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}
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goto errout;
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}
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/* On success, return the PID */
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sched_unlock();
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return pid;
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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 */
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