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