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/* sched_plugin.c -- core infrastructure for the scheduler plugin system
*
* This file includes the initialization of the plugin system, the no-op Linux
* scheduler plugin and some dummy functions.
*/
#include <linux/list.h>
#include <linux/spinlock.h>
#include <litmus/litmus.h>
#include <litmus/sched_plugin.h>
/*************************************************************
* Dummy plugin functions *
*************************************************************/
static void litmus_dummy_finish_switch(struct task_struct * prev)
{
}
static int litmus_dummy_schedule(struct task_struct * prev,
struct task_struct** next)
{
return 0;
}
static void litmus_dummy_scheduler_tick(void)
{
}
static long litmus_dummy_prepare_task(struct task_struct *t)
{
return 0;
}
static void litmus_dummy_wake_up_task(struct task_struct *task)
{
printk(KERN_WARNING "task %d: unhandled real-time wake up!\n",
task->pid);
}
static void litmus_dummy_task_blocks(struct task_struct *task)
{
}
static long litmus_dummy_tear_down(struct task_struct *task)
{
return 0;
}
static long litmus_dummy_sleep_next_period(void)
{
return -ENOSYS;
}
static long litmus_dummy_inherit_priority(struct pi_semaphore *sem,
struct task_struct *new_owner)
{
return -ENOSYS;
}
static long litmus_dummy_return_priority(struct pi_semaphore *sem)
{
return -ENOSYS;
}
static long litmus_dummy_pi_block(struct pi_semaphore *sem,
struct task_struct *new_waiter)
{
return -ENOSYS;
}
/* The default scheduler plugin. It doesn't do anything and lets Linux do its
* job.
*/
struct sched_plugin linux_sched_plugin = {
.plugin_name = "Linux",
.scheduler_tick = litmus_dummy_scheduler_tick,
.prepare_task = litmus_dummy_prepare_task,
.tear_down = litmus_dummy_tear_down,
.wake_up_task = litmus_dummy_wake_up_task,
.task_blocks = litmus_dummy_task_blocks,
.sleep_next_period = litmus_dummy_sleep_next_period,
.schedule = litmus_dummy_schedule,
.finish_switch = litmus_dummy_finish_switch,
.inherit_priority = litmus_dummy_inherit_priority,
.return_priority = litmus_dummy_return_priority,
.pi_block = litmus_dummy_pi_block
};
/*
* The reference to current plugin that is used to schedule tasks within
* the system. It stores references to actual function implementations
* Should be initialized by calling "init_***_plugin()"
*/
struct sched_plugin *curr_sched_plugin = &linux_sched_plugin;
/* the list of registered scheduling plugins */
static LIST_HEAD(sched_plugins);
static DEFINE_SPINLOCK(sched_plugins_lock);
#define CHECK(func) {\
if (!plugin->func) \
plugin->func = litmus_dummy_ ## func;}
/* FIXME: get reference to module */
int register_sched_plugin(struct sched_plugin* plugin)
{
printk(KERN_INFO "Registering LITMUS^RT plugin %s.\n",
plugin->plugin_name);
/* make sure we don't trip over null pointers later */
CHECK(finish_switch);
CHECK(schedule);
CHECK(scheduler_tick);
CHECK(wake_up_task);
CHECK(tear_down);
CHECK(task_blocks);
CHECK(prepare_task);
CHECK(sleep_next_period);
CHECK(inherit_priority);
CHECK(return_priority);
CHECK(pi_block);
spin_lock(&sched_plugins_lock);
list_add(&plugin->list, &sched_plugins);
spin_unlock(&sched_plugins_lock);
return 0;
}
/* FIXME: reference counting, etc. */
struct sched_plugin* find_sched_plugin(const char* name)
{
struct list_head *pos;
struct sched_plugin *plugin;
spin_lock(&sched_plugins_lock);
list_for_each(pos, &sched_plugins) {
plugin = list_entry(pos, struct sched_plugin, list);
if (!strcmp(plugin->plugin_name, name))
goto out_unlock;
}
plugin = NULL;
out_unlock:
spin_unlock(&sched_plugins_lock);
return plugin;
}
int print_sched_plugins(char* buf, int max)
{
int count = 0;
struct list_head *pos;
struct sched_plugin *plugin;
spin_lock(&sched_plugins_lock);
list_for_each(pos, &sched_plugins) {
plugin = list_entry(pos, struct sched_plugin, list);
count += snprintf(buf + count, max - count, "%s\n", plugin->plugin_name);
if (max - count <= 0)
break;
}
spin_unlock(&sched_plugins_lock);
return count;
}
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