/*
* litmus.c -- Implementation of the LITMUS syscalls,
* the LITMUS intialization code,
* and the procfs interface..
*/
#include <asm/uaccess.h>
#include <linux/uaccess.h>
#include <linux/sysrq.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/reboot.h>
#include <linux/stop_machine.h>
#include <linux/sched/rt.h>
#include <linux/rwsem.h>
#include <linux/interrupt.h>
#include <litmus/litmus.h>
#include <litmus/bheap.h>
#include <litmus/trace.h>
#include <litmus/rt_domain.h>
#include <litmus/litmus_proc.h>
#include <litmus/sched_trace.h>
#ifdef CONFIG_SCHED_CPU_AFFINITY
#include <litmus/affinity.h>
#endif
#ifdef CONFIG_SCHED_LITMUS_TRACEPOINT
#define CREATE_TRACE_POINTS
#include <trace/events/litmus.h>
#endif
/* Number of RT tasks that exist in the system */
atomic_t rt_task_count = ATOMIC_INIT(0);
#ifdef CONFIG_RELEASE_MASTER
/* current master CPU for handling timer IRQs */
atomic_t release_master_cpu = ATOMIC_INIT(NO_CPU);
#endif
static struct kmem_cache * bheap_node_cache;
extern struct kmem_cache * release_heap_cache;
struct bheap_node* bheap_node_alloc(int gfp_flags)
{
return kmem_cache_alloc(bheap_node_cache, gfp_flags);
}
void bheap_node_free(struct bheap_node* hn)
{
kmem_cache_free(bheap_node_cache, hn);
}
struct release_heap* release_heap_alloc(int gfp_flags);
void release_heap_free(struct release_heap* rh);
/**
* Get the quantum alignment as a cmdline option.
* Default is staggered quanta, as this results in lower overheads.
*/
static bool aligned_quanta = 0;
module_param(aligned_quanta, bool, 0644);
u64 cpu_stagger_offset(int cpu)
{
u64 offset = 0;
if (!aligned_quanta) {
offset = LITMUS_QUANTUM_LENGTH_NS;
do_div(offset, num_possible_cpus());
offset *= cpu;
}
return offset;
}
/*
* 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);
rcu_read_lock();
if (!(target = find_task_by_vpid(pid))) {
retval = -ESRCH;
rcu_read_unlock();
goto out_unlock;
}
rcu_read_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;
}
/* set relative deadline to be implicit if left unspecified */
if (tp.relative_deadline == 0)
tp.relative_deadline = tp.period;
if (tp.exec_cost <= 0)
goto out_unlock;
if (tp.period <= 0)
goto out_unlock;
if (min(tp.relative_deadline, tp.period) < tp.exec_cost) /*density check*/
{
printk(KERN_INFO "litmus: real-time task %d rejected "
"because task density > 1.0\n", pid);
goto out_unlock;
}
if (tp.cls != RT_CLASS_HARD &&
tp.cls != RT_CLASS_SOFT &&
tp.cls != RT_CLASS_BEST_EFFORT)
{
printk(KERN_INFO "litmus: real-time task %d rejected "
"because its class is invalid\n", pid);
goto out_unlock;
}
if (tp.budget_policy != NO_ENFORCEMENT &&
tp.budget_policy != QUANTUM_ENFORCEMENT &&
tp.budget_policy != PRECISE_ENFORCEMENT)
{
printk(KERN_INFO "litmus: real-time task %d rejected "
"because unsupported budget enforcement policy "
"specified (%d)\n",
pid, tp.budget_policy);
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_irq(&tasklist_lock);
rcu_read_lock();
source = find_task_by_vpid(pid);
rcu_read_unlock();
if (!source) {
retval = -ESRCH;
read_unlock_irq(&tasklist_lock);
goto out;
}
lp = source->rt_param.task_params;
read_unlock_irq(&tasklist_lock);
/* Do copying outside the lock */
retval =
copy_to_user(param, &lp, sizeof(lp)) ? -EFAULT : 0;
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 = {};
void* ctrl_page = NULL;
if (restore) {
/* Safe user-space provided configuration data.
* and allocated page. */
user_config = p->rt_param.task_params;
ctrl_page = p->rt_param.ctrl_page;
}
/* We probably should not be inheriting any task's priority
* at this point in time.
*/
WARN_ON(p->rt_param.inh_task);
/* Cleanup everything else. */
memset(&p->rt_param, 0, sizeof(p->rt_param));
/* Restore preserved fields. */
if (restore) {
p->rt_param.task_params = user_config;
p->rt_param.ctrl_page = ctrl_page;
}
}
long litmus_admit_task(struct task_struct* tsk)
{
long retval = 0;
BUG_ON(is_realtime(tsk));
tsk_rt(tsk)->heap_node = NULL;
tsk_rt(tsk)->rel_heap = NULL;
if (get_rt_relative_deadline(tsk) == 0 ||
get_exec_cost(tsk) >
min(get_rt_relative_deadline(tsk), get_rt_period(tsk)) ) {
TRACE_TASK(tsk,
"litmus admit: invalid task parameters "
"(e = %lu, p = %lu, d = %lu)\n",
get_exec_cost(tsk), get_rt_period(tsk),
get_rt_relative_deadline(tsk));
retval = -EINVAL;
goto out;
}
INIT_LIST_HEAD(&tsk_rt(tsk)->list);
/* allocate heap node for this task */
tsk_rt(tsk)->heap_node = bheap_node_alloc(GFP_ATOMIC);
tsk_rt(tsk)->rel_heap = release_heap_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;
goto out;
} else {
bheap_node_init(&tsk_rt(tsk)->heap_node, tsk);
}
preempt_disable();
retval = litmus->admit_task(tsk);
if (!retval) {
sched_trace_task_name(tsk);
sched_trace_task_param(tsk);
atomic_inc(&rt_task_count);
}
preempt_enable();
out:
if (retval) {
if (tsk_rt(tsk)->heap_node)
bheap_node_free(tsk_rt(tsk)->heap_node);
if (tsk_rt(tsk)->rel_heap)
release_heap_free(tsk_rt(tsk)->rel_heap);
}
return retval;
}
void litmus_clear_state(struct task_struct* tsk)
{
BUG_ON(bheap_node_in_heap(tsk_rt(tsk)->heap_node));
bheap_node_free(tsk_rt(tsk)->heap_node);
release_heap_free(tsk_rt(tsk)->rel_heap);
atomic_dec(&rt_task_count);
reinit_litmus_state(tsk, 1);
}
/* called from sched_setscheduler() */
void litmus_exit_task(struct task_struct* tsk)
{
if (is_realtime(tsk)) {
sched_trace_task_completion(tsk, 1);
litmus->task_exit(tsk);
}
}
static DECLARE_RWSEM(plugin_switch_mutex);
void litmus_plugin_switch_disable(void)
{
down_read(&plugin_switch_mutex);
}
void litmus_plugin_switch_enable(void)
{
up_read(&plugin_switch_mutex);
}
static int __do_plugin_switch(struct sched_plugin* plugin)
{
int ret;
/* don't switch if there are active real-time tasks */
if (atomic_read(&rt_task_count) == 0) {
TRACE("deactivating plugin %s\n", litmus->plugin_name);
ret = litmus->deactivate_plugin();
if (0 != ret)
goto out;
TRACE("activating plugin %s\n", plugin->plugin_name);
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:
TRACE("do_plugin_switch() => %d\n", ret);
return ret;
}
static atomic_t ready_to_switch;
static int do_plugin_switch(void *_plugin)
{
unsigned long flags;
int ret = 0;
local_save_flags(flags);
local_irq_disable();
hard_irq_disable();
if (atomic_dec_and_test(&ready_to_switch))
{
ret = __do_plugin_switch((struct sched_plugin*) _plugin);
atomic_set(&ready_to_switch, INT_MAX);
}
do {
cpu_relax();
} while (atomic_read(&ready_to_switch) != INT_MAX);
local_irq_restore(flags);
return ret;
}
/* 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).
*/
int switch_sched_plugin(struct sched_plugin* plugin)
{
int err;
struct domain_proc_info* domain_info;
BUG_ON(!plugin);
if (atomic_read(&rt_task_count) == 0) {
down_write(&plugin_switch_mutex);
deactivate_domain_proc();
get_online_cpus();
atomic_set(&ready_to_switch, num_online_cpus());
err = stop_cpus(cpu_online_mask, do_plugin_switch, plugin);
put_online_cpus();
if (!litmus->get_domain_proc_info(&domain_info))
activate_domain_proc(domain_info);
up_write(&plugin_switch_mutex);
return err;
} else
return -EBUSY;
}
/* 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);
/* Don't let the child be a real-time task. */
p->sched_reset_on_fork = 1;
} else
/* non-rt tasks might have ctrl_page set */
tsk_rt(p)->ctrl_page = NULL;
/* od tables are never inherited across a fork */
p->od_table = NULL;
}
/* 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);
if (tsk_rt(p)->ctrl_page) {
free_page((unsigned long) tsk_rt(p)->ctrl_page);
tsk_rt(p)->ctrl_page = NULL;
}
}
}
/* Called when dead_tsk is being deallocated
*/
void exit_litmus(struct task_struct *dead_tsk)
{
/* We also allow non-RT tasks to
* allocate control pages to allow
* measurements with non-RT tasks.
* So check if we need to free the page
* in any case.
*/
if (tsk_rt(dead_tsk)->ctrl_page) {
TRACE_TASK(dead_tsk,
"freeing ctrl_page %p\n",
tsk_rt(dead_tsk)->ctrl_page);
free_page((unsigned long) tsk_rt(dead_tsk)->ctrl_page);
}
/* Tasks should not be real-time tasks any longer at this point. */
BUG_ON(is_realtime(dead_tsk));
}
void litmus_do_exit(struct task_struct *exiting_tsk)
{
/* This task called do_exit(), but is still a real-time task. To avoid
* complications later, we force it to be a non-real-time task now. */
struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
TRACE_TASK(exiting_tsk, "exiting, demoted to SCHED_FIFO\n");
sched_setscheduler_nocheck(exiting_tsk, SCHED_FIFO, ¶m);
}
void litmus_dealloc(struct task_struct *tsk)
{
/* tsk is no longer a real-time task */
TRACE_TASK(tsk, "Deallocating real-time task data\n");
litmus->task_cleanup(tsk);
litmus_clear_state(tsk);
}
/* move current non-RT task to a specific CPU */
int litmus_be_migrate_to(int cpu)
{
struct cpumask single_cpu_aff;
cpumask_clear(&single_cpu_aff);
cpumask_set_cpu(cpu, &single_cpu_aff);
return sched_setaffinity(current->pid, &single_cpu_aff);
}
#ifdef CONFIG_MAGIC_SYSRQ
int sys_kill(int pid, int sig);
static void sysrq_handle_kill_rt_tasks(int key)
{
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
extern struct sched_plugin linux_sched_plugin;
static int litmus_shutdown_nb(struct notifier_block *unused1,
unsigned long unused2, void *unused3)
{
/* Attempt to switch back to regular Linux scheduling.
* Forces the active plugin to clean up.
*/
if (litmus != &linux_sched_plugin) {
int ret = switch_sched_plugin(&linux_sched_plugin);
if (ret) {
printk("Auto-shutdown of active Litmus plugin failed.\n");
}
}
return NOTIFY_DONE;
}
static struct notifier_block shutdown_notifier = {
.notifier_call = litmus_shutdown_nb,
};
/**
* Triggering hrtimers on specific cpus as required by arm_release_timer(_on)
*/
#ifdef CONFIG_SMP
/**
* hrtimer_pull - smp_call_function_single_async callback on remote cpu
*/
void hrtimer_pull(void *csd_info)
{
struct hrtimer_start_on_info *info = csd_info;
TRACE("pulled timer 0x%x\n", info->timer);
hrtimer_start_range_ns(info->timer, info->time, 0, info->mode);
}
/**
* hrtimer_start_on - trigger timer arming on remote cpu
* @cpu: remote cpu
* @info: save timer information for enqueuing on remote cpu
* @timer: timer to be pulled
* @time: expire time
* @mode: timer mode
*/
void hrtimer_start_on(int cpu, struct hrtimer_start_on_info *info,
struct hrtimer *timer, ktime_t time,
const enum hrtimer_mode mode)
{
info->timer = timer;
info->time = time;
info->mode = mode;
/* initialize call_single_data struct */
info->csd.func = &hrtimer_pull;
info->csd.info = info;
info->csd.flags = 0;
/* initiate pull */
preempt_disable();
if (cpu == smp_processor_id()) {
/* start timer locally; we may get called
* with rq->lock held, do not wake up anything
*/
TRACE("hrtimer_start_on: starting on local CPU\n");
__hrtimer_start_range_ns(info->timer, info->time,
0, info->mode, 0);
} else {
/* call hrtimer_pull() on remote cpu
* to start remote timer asynchronously
*/
TRACE("hrtimer_start_on: pulling to remote CPU\n");
smp_call_function_single_async(cpu, &info->csd);
}
preempt_enable();
}
#endif /* CONFIG_SMP */
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);
bheap_node_cache = KMEM_CACHE(bheap_node, SLAB_PANIC);
release_heap_cache = KMEM_CACHE(release_heap, 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();
register_reboot_notifier(&shutdown_notifier);
return 0;
}
static void _exit_litmus(void)
{
unregister_reboot_notifier(&shutdown_notifier);
exit_litmus_proc();
kmem_cache_destroy(bheap_node_cache);
kmem_cache_destroy(release_heap_cache);
}
module_init(_init_litmus);
module_exit(_exit_litmus);
