/* litmus.c -- Implementation of the LITMUS syscalls, the LITMUS intialization code, * and the procfs interface.. */ #include #include #include #include #include #include #include #include #include #include #include /* Number of RT tasks that exist in the system */ atomic_t rt_task_count = ATOMIC_INIT(0); static DEFINE_SPINLOCK(task_transition_lock); /* Give log messages sequential IDs. */ atomic_t __log_seq_no = ATOMIC_INIT(0); /* current master CPU for handling timer IRQs */ atomic_t release_master_cpu = ATOMIC_INIT(NO_CPU); static struct kmem_cache * heap_node_cache; struct heap_node* heap_node_alloc(int gfp_flags) { return kmem_cache_alloc(heap_node_cache, gfp_flags); } void heap_node_free(struct heap_node* hn) { kmem_cache_free(heap_node_cache, hn); } /* * sys_set_task_rt_param * @pid: Pid of the task which scheduling parameters must be changed * @param: New real-time extension parameters such as the execution cost and * period * Syscall for manipulating with task rt extension params * Returns EFAULT if param is NULL. * ESRCH if pid is not corrsponding * to a valid task. * EINVAL if either period or execution cost is <=0 * EPERM if pid is a real-time task * 0 if success * * Only non-real-time tasks may be configured with this system call * to avoid races with the scheduler. In practice, this means that a * task's parameters must be set _before_ calling sys_prepare_rt_task() * * find_task_by_vpid() assumes that we are in the same namespace of the * target. */ asmlinkage long sys_set_rt_task_param(pid_t pid, struct rt_task __user * param) { struct rt_task tp; struct task_struct *target; int retval = -EINVAL; printk("Setting up rt task parameters for process %d.\n", pid); if (pid < 0 || param == 0) { goto out; } if (copy_from_user(&tp, param, sizeof(tp))) { retval = -EFAULT; goto out; } /* Task search and manipulation must be protected */ read_lock_irq(&tasklist_lock); if (!(target = find_task_by_vpid(pid))) { retval = -ESRCH; goto out_unlock; } if (is_realtime(target)) { /* The task is already a real-time task. * We cannot not allow parameter changes at this point. */ retval = -EBUSY; goto out_unlock; } if (tp.exec_cost <= 0) goto out_unlock; if (tp.period <= 0) goto out_unlock; if (!cpu_online(tp.cpu)) goto out_unlock; if (tp.period < tp.exec_cost) { printk(KERN_INFO "litmus: real-time task %d rejected " "because wcet > period\n", pid); goto out_unlock; } target->rt_param.task_params = tp; retval = 0; out_unlock: read_unlock_irq(&tasklist_lock); out: return retval; } /* * Getter of task's RT params * returns EINVAL if param or pid is NULL * returns ESRCH if pid does not correspond to a valid task * returns EFAULT if copying of parameters has failed. * * find_task_by_vpid() assumes that we are in the same namespace of the * target. */ asmlinkage long sys_get_rt_task_param(pid_t pid, struct rt_task __user * param) { int retval = -EINVAL; struct task_struct *source; struct rt_task lp; if (param == 0 || pid < 0) goto out; read_lock(&tasklist_lock); if (!(source = find_task_by_vpid(pid))) { retval = -ESRCH; goto out_unlock; } lp = source->rt_param.task_params; read_unlock(&tasklist_lock); /* Do copying outside the lock */ retval = copy_to_user(param, &lp, sizeof(lp)) ? -EFAULT : 0; return retval; out_unlock: read_unlock(&tasklist_lock); out: return retval; } /* * This is the crucial function for periodic task implementation, * It checks if a task is periodic, checks if such kind of sleep * is permitted and calls plugin-specific sleep, which puts the * task into a wait array. * returns 0 on successful wakeup * returns EPERM if current conditions do not permit such sleep * returns EINVAL if current task is not able to go to sleep */ asmlinkage long sys_complete_job(void) { int retval = -EPERM; if (!is_realtime(current)) { retval = -EINVAL; goto out; } /* Task with negative or zero period cannot sleep */ if (get_rt_period(current) <= 0) { retval = -EINVAL; goto out; } /* The plugin has to put the task into an * appropriate queue and call schedule */ retval = litmus->complete_job(); out: return retval; } /* This is an "improved" version of sys_complete_job that * addresses the problem of unintentionally missing a job after * an overrun. * * returns 0 on successful wakeup * returns EPERM if current conditions do not permit such sleep * returns EINVAL if current task is not able to go to sleep */ asmlinkage long sys_wait_for_job_release(unsigned int job) { int retval = -EPERM; if (!is_realtime(current)) { retval = -EINVAL; goto out; } /* Task with negative or zero period cannot sleep */ if (get_rt_period(current) <= 0) { retval = -EINVAL; goto out; } retval = 0; /* first wait until we have "reached" the desired job * * This implementation has at least two problems: * * 1) It doesn't gracefully handle the wrap around of * job_no. Since LITMUS is a prototype, this is not much * of a problem right now. * * 2) It is theoretically racy if a job release occurs * between checking job_no and calling sleep_next_period(). * A proper solution would requiring adding another callback * in the plugin structure and testing the condition with * interrupts disabled. * * FIXME: At least problem 2 should be taken care of eventually. */ while (!retval && job > current->rt_param.job_params.job_no) /* If the last job overran then job <= job_no and we * don't send the task to sleep. */ retval = litmus->complete_job(); out: return retval; } /* This is a helper syscall to query the current job sequence number. * * returns 0 on successful query * returns EPERM if task is not a real-time task. * returns EFAULT if &job is not a valid pointer. */ asmlinkage long sys_query_job_no(unsigned int __user *job) { int retval = -EPERM; if (is_realtime(current)) retval = put_user(current->rt_param.job_params.job_no, job); return retval; } /* sys_null_call() is only used for determining raw system call * overheads (kernel entry, kernel exit). It has no useful side effects. * If ts is non-NULL, then the current Feather-Trace time is recorded. */ asmlinkage long sys_null_call(cycles_t __user *ts) { long ret = 0; cycles_t now; if (ts) { now = get_cycles(); ret = put_user(now, ts); } return ret; } /* p is a real-time task. Re-init its state as a best-effort task. */ static void reinit_litmus_state(struct task_struct* p, int restore) { struct rt_task user_config = {}; __user short *np_flag = NULL; if (restore) { /* Safe user-space provided configuration data. */ user_config = p->rt_param.task_params; np_flag = p->rt_param.np_flag; } /* We probably should not be inheriting any task's priority * at this point in time. */ WARN_ON(p->rt_param.inh_task); /* We need to restore the priority of the task. */ // __setscheduler(p, p->rt_param.old_policy, p->rt_param.old_prio); /* Cleanup everything else. */ memset(&p->rt_param, 0, sizeof(user_config)); /* Restore preserved fields. */ if (restore) { p->rt_param.task_params = user_config; p->rt_param.np_flag = np_flag; } } long litmus_admit_task(struct task_struct* tsk) { long retval = 0; unsigned long flags; BUG_ON(is_realtime(tsk)); if (get_rt_period(tsk) == 0 || get_exec_cost(tsk) > get_rt_period(tsk)) { TRACE_TASK(tsk, "litmus admit: invalid task parameters " "(%lu, %lu)\n", get_exec_cost(tsk), get_rt_period(tsk)); return -EINVAL; } if (!cpu_online(get_partition(tsk))) { TRACE_TASK(tsk, "litmus admit: cpu %d is not online\n", get_partition(tsk)); return -EINVAL; } INIT_LIST_HEAD(&tsk_rt(tsk)->list); /* avoid scheduler plugin changing underneath us */ spin_lock_irqsave(&task_transition_lock, flags); /* allocate heap node for this task */ tsk_rt(tsk)->heap_node = heap_node_alloc(GFP_ATOMIC); if (!tsk_rt(tsk)->heap_node || !tsk_rt(tsk)->rel_heap) { printk(KERN_WARNING "litmus: no more heap node memory!?\n"); retval = -ENOMEM; heap_node_free(tsk_rt(tsk)->heap_node); } else heap_node_init(&tsk_rt(tsk)->heap_node, tsk); if (!retval) retval = litmus->admit_task(tsk); if (!retval) { sched_trace_task_name(tsk); sched_trace_task_param(tsk); atomic_inc(&rt_task_count); } spin_unlock_irqrestore(&task_transition_lock, flags); return retval; } void litmus_exit_task(struct task_struct* tsk) { if (is_realtime(tsk)) { sched_trace_task_completion(tsk, 1); litmus->task_exit(tsk); BUG_ON(heap_node_in_heap(tsk_rt(tsk)->heap_node)); heap_node_free(tsk_rt(tsk)->heap_node); atomic_dec(&rt_task_count); reinit_litmus_state(tsk, 1); } } /* Switching a plugin in use is tricky. * We must watch out that no real-time tasks exists * (and that none is created in parallel) and that the plugin is not * currently in use on any processor (in theory). * * For now, we don't enforce the second part since it is unlikely to cause * any trouble by itself as long as we don't unload modules. */ int switch_sched_plugin(struct sched_plugin* plugin) { unsigned long flags; int ret = 0; BUG_ON(!plugin); /* stop task transitions */ spin_lock_irqsave(&task_transition_lock, flags); /* don't switch if there are active real-time tasks */ if (atomic_read(&rt_task_count) == 0) { ret = litmus->deactivate_plugin(); if (0 != ret) goto out; ret = plugin->activate_plugin(); if (0 != ret) { printk(KERN_INFO "Can't activate %s (%d).\n", plugin->plugin_name, ret); plugin = &linux_sched_plugin; } printk(KERN_INFO "Switching to LITMUS^RT plugin %s.\n", plugin->plugin_name); litmus = plugin; } else ret = -EBUSY; out: spin_unlock_irqrestore(&task_transition_lock, flags); return ret; } /* Called upon fork. * p is the newly forked task. */ void litmus_fork(struct task_struct* p) { if (is_realtime(p)) /* clean out any litmus related state, don't preserve anything*/ reinit_litmus_state(p, 0); } /* Called upon execve(). * current is doing the exec. * Don't let address space specific stuff leak. */ void litmus_exec(void) { struct task_struct* p = current; if (is_realtime(p)) { WARN_ON(p->rt_param.inh_task); p->rt_param.np_flag = NULL; } } void exit_litmus(struct task_struct *dead_tsk) { if (is_realtime(dead_tsk)) litmus_exit_task(dead_tsk); } #ifdef CONFIG_MAGIC_SYSRQ int sys_kill(int pid, int sig); static void sysrq_handle_kill_rt_tasks(int key, struct tty_struct *tty) { struct task_struct *t; read_lock(&tasklist_lock); for_each_process(t) { if (is_realtime(t)) { sys_kill(t->pid, SIGKILL); } } read_unlock(&tasklist_lock); } static struct sysrq_key_op sysrq_kill_rt_tasks_op = { .handler = sysrq_handle_kill_rt_tasks, .help_msg = "quit-rt-tasks(X)", .action_msg = "sent SIGKILL to all LITMUS^RT real-time tasks", }; #endif static int proc_read_stats(char *page, char **start, off_t off, int count, int *eof, void *data) { int len; len = snprintf(page, PAGE_SIZE, "real-time tasks = %d\n" "ready for release = %d\n", atomic_read(&rt_task_count), 0); return len; } static int proc_read_plugins(char *page, char **start, off_t off, int count, int *eof, void *data) { int len; len = print_sched_plugins(page, PAGE_SIZE); return len; } static int proc_read_curr(char *page, char **start, off_t off, int count, int *eof, void *data) { int len; len = snprintf(page, PAGE_SIZE, "%s\n", litmus->plugin_name); return len; } static int proc_write_curr(struct file *file, const char *buffer, unsigned long count, void *data) { int len, ret; char name[65]; struct sched_plugin* found; if(count > 64) len = 64; else len = count; if(copy_from_user(name, buffer, len)) return -EFAULT; name[len] = '\0'; /* chomp name */ if (len > 1 && name[len - 1] == '\n') name[len - 1] = '\0'; found = find_sched_plugin(name); if (found) { ret = switch_sched_plugin(found); if (ret != 0) printk(KERN_INFO "Could not switch plugin: %d\n", ret); } else printk(KERN_INFO "Plugin '%s' is unknown.\n", name); return len; } static int proc_read_release_master(char *page, char **start, off_t off, int count, int *eof, void *data) { int len, master; master = atomic_read(&release_master_cpu); if (master == NO_CPU) len = snprintf(page, PAGE_SIZE, "NO_CPU\n"); else len = snprintf(page, PAGE_SIZE, "%d\n", master); return len; } static int proc_write_release_master(struct file *file, const char *buffer, unsigned long count, void *data) { int cpu, err, online = 0; char msg[64]; if (count > 63) return -EINVAL; if (copy_from_user(msg, buffer, count)) return -EFAULT; /* terminate */ msg[count] = '\0'; /* chomp */ if (count > 1 && msg[count - 1] == '\n') msg[count - 1] = '\0'; if (strcmp(msg, "NO_CPU") == 0) { atomic_set(&release_master_cpu, NO_CPU); return count; } else { err = sscanf(msg, "%d", &cpu); if (err == 1 && cpu >= 0 && (online = cpu_online(cpu))) { atomic_set(&release_master_cpu, cpu); return count; } else { TRACE("invalid release master: '%s' " "(err:%d cpu:%d online:%d)\n", msg, err, cpu, online); return -EINVAL; } } } static struct proc_dir_entry *litmus_dir = NULL, *curr_file = NULL, *stat_file = NULL, *plugs_file = NULL, *release_master_file = NULL; static int __init init_litmus_proc(void) { litmus_dir = proc_mkdir("litmus", NULL); if (!litmus_dir) { printk(KERN_ERR "Could not allocate LITMUS^RT procfs entry.\n"); return -ENOMEM; } curr_file = create_proc_entry("active_plugin", 0644, litmus_dir); if (!curr_file) { printk(KERN_ERR "Could not allocate active_plugin " "procfs entry.\n"); return -ENOMEM; } curr_file->read_proc = proc_read_curr; curr_file->write_proc = proc_write_curr; release_master_file = create_proc_entry("release_master", 0644, litmus_dir); if (!release_master_file) { printk(KERN_ERR "Could not allocate release_master " "procfs entry.\n"); return -ENOMEM; } release_master_file->read_proc = proc_read_release_master; release_master_file->write_proc = proc_write_release_master; stat_file = create_proc_read_entry("stats", 0444, litmus_dir, proc_read_stats, NULL); plugs_file = create_proc_read_entry("plugins", 0444, litmus_dir, proc_read_plugins, NULL); return 0; } static void exit_litmus_proc(void) { if (plugs_file) remove_proc_entry("plugins", litmus_dir); if (stat_file) remove_proc_entry("stats", litmus_dir); if (curr_file) remove_proc_entry("active_plugin", litmus_dir); if (litmus_dir) remove_proc_entry("litmus", NULL); } extern struct sched_plugin linux_sched_plugin; static int __init _init_litmus(void) { /* Common initializers, * mode change lock is used to enforce single mode change * operation. */ printk("Starting LITMUS^RT kernel\n"); register_sched_plugin(&linux_sched_plugin); heap_node_cache = KMEM_CACHE(heap_node, SLAB_PANIC); #ifdef CONFIG_MAGIC_SYSRQ /* offer some debugging help */ if (!register_sysrq_key('x', &sysrq_kill_rt_tasks_op)) printk("Registered kill rt tasks magic sysrq.\n"); else printk("Could not register kill rt tasks magic sysrq.\n"); #endif init_litmus_proc(); return 0; } static void _exit_litmus(void) { exit_litmus_proc(); kmem_cache_destroy(heap_node_cache); } module_init(_init_litmus); module_exit(_exit_litmus);