/**************************************************************************** * 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 #include #include #include #include #include #include #include #include #include #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) { 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 * * 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: * * 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 process ID of new task on success. * Otherwise, a negative 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. * ****************************************************************************/ int task_spawn(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[]) { struct sched_param param; pid_t proxy; pid_t pid = INVALID_PROCESS_ID; #ifdef CONFIG_SCHED_WAITPID int status; #endif int ret; sinfo("name=%s entry=%p file_actions=%p attr=%p argv=%p\n", 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)) { ret = nxtask_spawn_exec(&pid, name, entry, attr, argv); if (ret < 0) { return ret; } return pid; } /* 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); g_spawn_parms.pid = NULL; 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 = nx_waitpid(proxy, &status, 0); if (ret < 0) { 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; if (ret < 0) { goto errout_with_lock; } ret = (int)pid; errout_with_lock: #ifdef CONFIG_SCHED_WAITPID sched_unlock(); #endif g_spawn_parms.pid = NULL; spawn_semgive(&g_spawn_parmsem); return ret; } #endif /* CONFIG_BUILD_KERNEL */