463 lines
15 KiB
C
463 lines
15 KiB
C
/****************************************************************************
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* sched/task/task_spawn.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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 <sched.h>
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#include <spawn.h>
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#include <assert.h>
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#include <debug.h>
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#include <errno.h>
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#include <nuttx/sched.h>
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#include <nuttx/kthread.h>
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#include <nuttx/spawn.h>
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#include "sched/sched.h"
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#include "group/group.h"
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#include "task/spawn.h"
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#include "task/task.h"
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#ifndef CONFIG_BUILD_KERNEL
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxtask_spawn_exec
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*
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* Description:
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* Execute the task from the file system.
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*
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* Input Parameters:
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*
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* pidp - Upon successful completion, this will return the task ID of the
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* child task in the variable pointed to by a non-NULL 'pid' argument.|
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*
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* name - The name to assign to the child task.
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*
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* entry - The child task's entry point (an address in memory)
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*
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* attr - If the value of the 'attr' parameter is NULL, the all default
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* values for the POSIX spawn attributes will be used. Otherwise, the
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* attributes will be set according to the spawn flags. The
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* following spawn flags are supported:
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*
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* - POSIX_SPAWN_SETSCHEDPARAM: Set new tasks priority to the sched_param
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* value.
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* - POSIX_SPAWN_SETSCHEDULER: Set the new tasks scheduler priority to
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* the sched_policy value.
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*
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* NOTE: POSIX_SPAWN_SETSIGMASK is handled in nxtask_spawn_proxy().
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*
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* argv - argv[] is the argument list for the new task. argv[] is an
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* array of pointers to null-terminated strings. The list is terminated
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* with a null pointer.
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*
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* envp - A pointer to an array of environment strings. Terminated with
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* a NULL entry.
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*
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* Returned Value:
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* This function will return zero on success. Otherwise, an error number
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* will be returned as the function return value to indicate the error.
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* This errno value may be that set by execv(), sched_setpolicy(), or
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* sched_setparam().
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*
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****************************************************************************/
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static int nxtask_spawn_exec(FAR pid_t *pidp, FAR const char *name,
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main_t entry, FAR const posix_spawnattr_t *attr,
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FAR char * const *argv, FAR char * const envp[])
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{
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FAR void *stackaddr = NULL;
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size_t stacksize;
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int priority;
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int pid;
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int ret = OK;
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/* Disable pre-emption so that we can modify the task parameters after
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* we start the new task; the new task will not actually begin execution
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* until we re-enable pre-emption.
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*/
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sched_lock();
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/* Use the default priority and stack size if no attributes are provided */
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if (attr)
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{
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priority = attr->priority;
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stacksize = attr->stacksize;
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stackaddr = attr->stackaddr;
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}
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else
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{
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struct sched_param param;
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/* Set the default priority to the same priority as this task */
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ret = nxsched_get_param(0, ¶m);
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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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priority = param.sched_priority;
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stacksize = CONFIG_POSIX_SPAWN_DEFAULT_STACKSIZE;
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}
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/* Start the task */
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pid = nxtask_create(name, priority, stackaddr,
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stacksize, entry, argv, envp);
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if (pid < 0)
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{
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ret = pid;
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serr("ERROR: nxtask_create failed: %d\n", ret);
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goto errout;
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}
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/* Return the task ID to the caller */
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if (pid)
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{
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*pidp = pid;
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}
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/* Now set the attributes. Note that we ignore all of the return values
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* here because we have already successfully started the task. If we
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* return an error value, then we would also have to stop the task.
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*/
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if (attr)
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{
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spawn_execattrs(pid, attr);
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}
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/* Re-enable pre-emption and return */
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errout:
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sched_unlock();
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return ret;
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}
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/****************************************************************************
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* Name: nxtask_spawn_proxy
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*
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* Description:
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* Perform file_actions, then execute the task from the file system.
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*
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* Do we really need a proxy task in this case? Isn't that wasteful?
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*
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* Q: Why can we do what we need to do here and the just call the
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* new task's entry point.
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* A: This would require setting up the name, priority, and stacksize from
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* the task_spawn, but it do-able. The only issue I can think of is
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* that NuttX supports task_restart(), and you would never be able to
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* restart a task from this point.
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*
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* Q: Why not use a starthook so that there is callout from nxtask_start()
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* to perform these operations?
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* A: Good idea, except that existing nxtask_starthook() implementation
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* cannot be used here unless we get rid of task_create and, instead,
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* use nxtask_init() and nxtask_activate(). start_taskhook() could then
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* be called between nxtask_init() and nxtask_activate().
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* task_restart() would still be an issue.
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*
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* Input Parameters:
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* argc, argv - Ignored. The task's start-up parameters are passed via the
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* semaphore-protected global structure g_spawn_parms.
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*
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* Returned Value:
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* Standard task return value.
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*
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****************************************************************************/
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static int nxtask_spawn_proxy(int argc, FAR char *argv[])
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{
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int ret;
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/* Perform file actions and/or set a custom signal mask. We get here only
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* if the file_actions parameter to task_spawn[p] was non-NULL and/or the
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* option to change the signal mask was selected.
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*/
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UNUSED(argc);
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UNUSED(argv);
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DEBUGASSERT(g_spawn_parms.file_actions ||
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(g_spawn_parms.attr &&
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(g_spawn_parms.attr->flags & POSIX_SPAWN_SETSIGMASK) != 0));
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/* Set the attributes and perform the file actions as appropriate */
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ret = spawn_proxyattrs(g_spawn_parms.attr, g_spawn_parms.file_actions);
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if (ret == OK)
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{
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/* Start the task */
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ret = nxtask_spawn_exec(g_spawn_parms.pid, g_spawn_parms.u.task.name,
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g_spawn_parms.u.task.entry, g_spawn_parms.attr,
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g_spawn_parms.argv, g_spawn_parms.envp);
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#ifdef CONFIG_SCHED_HAVE_PARENT
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if (ret == OK)
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{
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/* Change of the parent of the task we just spawned to our parent.
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* What should we do in the event of a failure?
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*/
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int tmp = task_reparent(0, *g_spawn_parms.pid);
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if (tmp < 0)
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{
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serr("ERROR: task_reparent() failed: %d\n", tmp);
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}
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}
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#endif
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}
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/* Post the semaphore to inform the parent task that we have completed
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* what we need to do.
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*/
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g_spawn_parms.result = ret;
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#ifndef CONFIG_SCHED_WAITPID
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nxsem_post(&g_spawn_execsem);
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#endif
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return OK;
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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: task_spawn
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*
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* Description:
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* The task_spawn() function will create a new, child task, where the
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* entry point to the task is an address in memory.
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*
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* Input Parameters:
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*
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* name - The name to assign to the child task.
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*
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* entry - The child task's entry point (an address in memory)
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*
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* file_actions - If 'file_actions' is a null pointer, then file
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* descriptors open in the calling process will remain open in the
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* child process (unless CONFIG_FDCLONE_STDIO is defined). If
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* 'file_actions' is not NULL, then the file descriptors open in the
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* child process will be those open in the calling process as modified
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* by the spawn file actions object pointed to by file_actions.
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*
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* attr - If the value of the 'attr' parameter is NULL, the all default
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* values for the POSIX spawn attributes will be used. Otherwise, the
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* attributes will be set according to the spawn flags. The
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* posix_spawnattr_t spawn attributes object type is defined in spawn.h.
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* It will contains these attributes, not all of which are supported by
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* NuttX:
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*
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* - POSIX_SPAWN_SETPGROUP: Setting of the new task's process group is
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* not supported. NuttX does not support process groups.
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* - POSIX_SPAWN_SETSCHEDPARAM: Set new tasks priority to the sched_param
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* value.
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* - POSIX_SPAWN_SETSCHEDULER: Set the new task's scheduler policy to
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* the sched_policy value.
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* - POSIX_SPAWN_RESETIDS: Resetting of the effective user ID of the
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* child process is not supported. NuttX does not support effective
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* user IDs.
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* - POSIX_SPAWN_SETSIGMASK: Set the new task's signal mask.
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* - POSIX_SPAWN_SETSIGDEF: Resetting signal default actions is not
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* supported. NuttX does not support default signal actions.
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*
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* And the non-standard:
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*
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* - TASK_SPAWN_SETSTACKSIZE: Set the stack size for the new task.
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*
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* argv - argv[] is the argument list for the new task. argv[] is an
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* array of pointers to null-terminated strings. The list is terminated
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* with a null pointer.
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*
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* envp - envp[] is an array of character pointers to null-terminated
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* strings that provide the environment for the new process image.
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*
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* Returned Value:
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* task_spawn() will return process ID of new task on success.
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* Otherwise, a negative number will be returned as the function return
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* value to indicate the error:
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*
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* - EINVAL: The value specified by 'file_actions' or 'attr' is invalid.
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* - Any errors that might have been return if vfork() and excec[l|v]()
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* had been called.
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*
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****************************************************************************/
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int task_spawn(FAR const char *name, main_t entry,
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FAR const posix_spawn_file_actions_t *file_actions,
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FAR const posix_spawnattr_t *attr,
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FAR char * const argv[], FAR char * const envp[])
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{
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struct sched_param param;
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pid_t proxy;
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pid_t pid = INVALID_PROCESS_ID;
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#ifdef CONFIG_SCHED_WAITPID
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int status;
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#endif
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int ret;
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sinfo("name=%s entry=%p file_actions=%p attr=%p argv=%p\n",
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name, entry, file_actions, attr, argv);
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/* If there are no file actions to be performed and there is no change to
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* the signal mask, then start the new child task directly from the parent
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* task.
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*/
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if ((file_actions == NULL || *file_actions == NULL) &&
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(attr == NULL || (attr->flags & POSIX_SPAWN_SETSIGMASK) == 0))
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{
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ret = nxtask_spawn_exec(&pid, name, entry, attr, argv, envp);
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if (ret < 0)
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{
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return ret;
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}
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return pid;
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}
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/* Otherwise, we will have to go through an intermediary/proxy task in
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* order to perform the I/O redirection. This would be a natural place to
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* fork(). However, true fork() behavior requires an MMU and most
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* implementations of vfork() are not capable of these operations.
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*
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* Even without fork(), we can still do the job, but parameter passing is
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* messier. Unfortunately, there is no (clean) way to pass binary values
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* as a task parameter, so we will use a semaphore-protected global
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* structure.
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*/
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/* Get exclusive access to the global parameter structure */
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ret = nxmutex_lock(&g_spawn_parmlock);
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if (ret < 0)
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{
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serr("ERROR: nxmutex_lock failed: %d\n", ret);
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return ret;
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}
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/* Populate the parameter structure */
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g_spawn_parms.result = ENOSYS;
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g_spawn_parms.pid = &pid;
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g_spawn_parms.file_actions = file_actions ? *file_actions : NULL;
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g_spawn_parms.attr = attr;
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g_spawn_parms.argv = argv;
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g_spawn_parms.envp = envp;
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g_spawn_parms.u.task.name = name;
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g_spawn_parms.u.task.entry = entry;
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/* Get the priority of this (parent) task */
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ret = nxsched_get_param(0, ¶m);
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if (ret < 0)
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{
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serr("ERROR: nxsched_get_param failed: %d\n", ret);
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g_spawn_parms.pid = NULL;
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nxmutex_unlock(&g_spawn_parmlock);
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return ret;
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}
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#ifdef CONFIG_SCHED_WAITPID
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/* Disable pre-emption so that the proxy does not run until waitpid
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* is called. This is probably unnecessary since the nxtask_spawn_proxy
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* has the same priority as this thread; it should be schedule behind
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* this task in the ready-to-run list.
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*
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* REVISIT: This will may not have the desired effect in SMP mode.
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*/
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sched_lock();
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#endif
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/* Start the intermediary/proxy task at the same priority as the parent
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* task.
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*/
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proxy = nxtask_create("nxtask_spawn_proxy", param.sched_priority,
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NULL, CONFIG_POSIX_SPAWN_PROXY_STACKSIZE,
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nxtask_spawn_proxy, NULL, NULL);
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if (proxy < 0)
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{
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ret = proxy;
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serr("ERROR: Failed to start nxtask_spawn_proxy: %d\n", ret);
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goto errout_with_lock;
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}
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/* Wait for the proxy to complete its job */
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#ifdef CONFIG_SCHED_WAITPID
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/* REVISIT: This should not call waitpid() directly. waitpid is a
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* cancellation point and modifies the errno value. It is inappropriate
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* for use within the OS.
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*/
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ret = nxsched_waitpid(proxy, &status, 0);
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if (ret < 0)
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{
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serr("ERROR: waitpid() failed: %d\n", ret);
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goto errout_with_lock;
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}
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#else
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ret = nxsem_wait_uninterruptible(&g_spawn_execsem);
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if (ret < 0)
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{
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serr("ERROR: g_spawn_execsem() failed: %d\n", ret);
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goto errout_with_lock;
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}
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#endif
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/* Get the result and relinquish our access to the parameter structure */
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ret = -g_spawn_parms.result;
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if (ret < 0)
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{
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goto errout_with_lock;
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}
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ret = (int)pid;
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errout_with_lock:
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#ifdef CONFIG_SCHED_WAITPID
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sched_unlock();
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#endif
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g_spawn_parms.pid = NULL;
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nxmutex_unlock(&g_spawn_parmlock);
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return ret;
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}
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#endif /* CONFIG_BUILD_KERNEL */
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