add G-EDF, a version of GSN-EDF with synchronization support ripped out

a good base version for other schedulers

2 files changed, 504 insertions, 1 deletions

diff --git a/litmus/Makefile b/litmus/Makefile
index 340c43c84f..c2c88cc9f6 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -10,7 +10,8 @@ obj-y     = sched_plugin.o litmus.o \
             sched_psn_edf.o \
             sched_cedf.o \
             sched_pfair.o \
-            sched_gq_edf.o
+            sched_gq_edf.o \
+            sched_gedf.o
 
 obj-$(CONFIG_FEATHER_TRACE) += trace.o ft_event.o ftdev.o
 obj-$(CONFIG_SCHED_TASK_TRACE) += sched_task_trace.o
diff --git a/litmus/sched_gedf.c b/litmus/sched_gedf.c
new file mode 100644
index 0000000000..e22e847c5f
--- /dev/null
+++ b/litmus/sched_gedf.c
@@ -0,0 +1,502 @@
+#include <linux/spinlock.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+
+#include <litmus/litmus.h>
+#include <litmus/jobs.h>
+#include <litmus/sched_plugin.h>
+#include <litmus/edf_common.h>
+#include <litmus/sched_trace.h>
+
+#include <litmus/heap.h>
+
+#include <linux/module.h>
+
+/* cpu_entry_t - maintain the linked and scheduled state
+ */
+typedef struct  {
+        int                     cpu;
+        struct task_struct*     linked;         /* only RT tasks */
+        struct task_struct*     scheduled;      /* only RT tasks */
+        atomic_t                will_schedule;  /* prevent unneeded IPIs */
+        struct heap_node*       hn;
+} cpu_entry_t;
+DEFINE_PER_CPU(cpu_entry_t, gedf_cpu_entries);
+
+cpu_entry_t* gedf_cpus[NR_CPUS];
+
+#define set_will_schedule() \
+        (atomic_set(&__get_cpu_var(gedf_cpu_entries).will_schedule, 1))
+#define clear_will_schedule() \
+        (atomic_set(&__get_cpu_var(gedf_cpu_entries).will_schedule, 0))
+#define test_will_schedule(cpu) \
+        (atomic_read(&per_cpu(gedf_cpu_entries, cpu).will_schedule))
+
+
+#define NO_CPU 0xffffffff
+
+/* the cpus queue themselves according to priority in here */
+static struct heap_node gedf_heap_node[NR_CPUS];
+static struct heap      gedf_cpu_heap;
+
+static rt_domain_t gedf;
+#define gedf_lock (gedf.ready_lock)
+
+
+static int cpu_lower_prio(struct heap_node *_a, struct heap_node *_b)
+{
+        cpu_entry_t *a, *b;
+        a = _a->value;
+        b = _b->value;
+        /* Note that a and b are inverted: we want the lowest-priority CPU at
+         * the top of the heap.
+         */
+        return edf_higher_prio(b->linked, a->linked);
+}
+
+/* update_cpu_position - Move the cpu entry to the correct place to maintain
+ *                       order in the cpu queue. Caller must hold gedf lock.
+ */
+static void update_cpu_position(cpu_entry_t *entry)
+{
+        if (likely(heap_node_in_heap(entry->hn)))
+                heap_delete(cpu_lower_prio, &gedf_cpu_heap, entry->hn);
+        heap_insert(cpu_lower_prio, &gedf_cpu_heap, entry->hn);
+}
+
+/* caller must hold gedf lock */
+static cpu_entry_t* lowest_prio_cpu(void)
+{
+        struct heap_node* hn;
+        hn = heap_peek(cpu_lower_prio, &gedf_cpu_heap);
+        return hn->value;
+}
+
+
+/* link_task_to_cpu - Update the link of a CPU.
+ *                    Handles the case where the to-be-linked task is already
+ *                    scheduled on a different CPU.
+ */
+static noinline void link_task_to_cpu(struct task_struct* linked,
+                                      cpu_entry_t *entry)
+{
+        cpu_entry_t *sched;
+        struct task_struct* tmp;
+        int on_cpu;
+
+        BUG_ON(linked && !is_realtime(linked));
+
+        /* Currently linked task is set to be unlinked. */
+        if (entry->linked) {
+                entry->linked->rt_param.linked_on = NO_CPU;
+        }
+
+        /* Link new task to CPU. */
+        if (linked) {
+                set_rt_flags(linked, RT_F_RUNNING);
+                /* handle task is already scheduled somewhere! */
+                on_cpu = linked->rt_param.scheduled_on;
+                if (on_cpu != NO_CPU) {
+                        sched = &per_cpu(gedf_cpu_entries, on_cpu);
+                        /* this should only happen if not linked already */
+                        BUG_ON(sched->linked == linked);
+
+                        /* If we are already scheduled on the CPU to which we
+                         * wanted to link, we don't need to do the swap --
+                         * we just link ourselves to the CPU and depend on
+                         * the caller to get things right.
+                         */
+                        if (entry != sched) {
+                                TRACE_TASK(linked,
+                                           "already scheduled on %d, updating link.\n",
+                                           sched->cpu);
+                                tmp = sched->linked;
+                                linked->rt_param.linked_on = sched->cpu;
+                                sched->linked = linked;
+                                update_cpu_position(sched);
+                                linked = tmp;
+                        }
+                }
+                if (linked) /* might be NULL due to swap */
+                        linked->rt_param.linked_on = entry->cpu;
+        }
+        entry->linked = linked;
+        if (linked)
+                TRACE_TASK(linked, "linked to %d.\n", entry->cpu);
+        else
+                TRACE("NULL linked to %d.\n", entry->cpu);
+        update_cpu_position(entry);
+}
+
+/* unlink - Make sure a task is not linked any longer to an entry
+ *          where it was linked before. Must hold gedf_lock.
+ */
+static noinline void unlink(struct task_struct* t)
+{
+        cpu_entry_t *entry;
+
+        if (unlikely(!t)) {
+                TRACE_BUG_ON(!t);
+                return;
+        }
+
+        if (t->rt_param.linked_on != NO_CPU) {
+                /* unlink */
+                entry = &per_cpu(gedf_cpu_entries, t->rt_param.linked_on);
+                t->rt_param.linked_on = NO_CPU;
+                link_task_to_cpu(NULL, entry);
+        } else if (is_queued(t)) {
+                /* This is an interesting situation: t is scheduled,
+                 * but was just recently unlinked.  It cannot be
+                 * linked anywhere else (because then it would have
+                 * been relinked to this CPU), thus it must be in some
+                 * queue. We must remove it from the list in this
+                 * case.
+                 */
+                remove(&gedf, t);
+        }
+}
+
+
+/* preempt - force a CPU to reschedule
+ */
+static noinline void preempt(cpu_entry_t *entry)
+{
+        if (smp_processor_id() == entry->cpu) {
+                set_tsk_need_resched(current);
+        } else
+                /* in case that it is a remote CPU we have to defer the
+                 * the decision to the remote CPU
+                 */
+                if (!test_will_schedule(entry->cpu))
+                        smp_send_reschedule(entry->cpu);
+}
+
+/* requeue - Put an unlinked task into gsn-edf domain.
+ *           Caller must hold gedf_lock.
+ */
+static noinline void requeue(struct task_struct* task)
+{
+        BUG_ON(!task);
+        /* sanity check before insertion */
+        BUG_ON(is_queued(task));
+
+        if (is_released(task, litmus_clock()))
+                __add_ready(&gedf, task);
+        else {
+                /* it has got to wait */
+                add_release(&gedf, task);
+        }
+}
+
+/* check for any necessary preemptions */
+static void check_for_preemptions(void)
+{
+        struct task_struct *task;
+        cpu_entry_t* last;
+
+        for(last = lowest_prio_cpu();
+            edf_preemption_needed(&gedf, last->linked);
+            last = lowest_prio_cpu()) {
+                /* preemption necessary */
+                task = __take_ready(&gedf);
+                TRACE("check_for_preemptions: attempting to link task %d to %d\n",
+                      task->pid, last->cpu);
+                if (last->linked)
+                        requeue(last->linked);
+                link_task_to_cpu(task, last);
+                preempt(last);
+        }
+}
+
+/* gedf_job_arrival: task is either resumed or released */
+static noinline void gedf_job_arrival(struct task_struct* task)
+{
+        BUG_ON(!task);
+
+        requeue(task);
+        check_for_preemptions();
+}
+
+static void gedf_release_jobs(rt_domain_t* rt, struct heap* tasks)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&gedf_lock, flags);
+
+        __merge_ready(rt, tasks);
+        check_for_preemptions();
+
+        spin_unlock_irqrestore(&gedf_lock, flags);
+}
+
+/* caller holds gedf_lock */
+static noinline void job_completion(struct task_struct *t, int forced)
+{
+        BUG_ON(!t);
+
+        sched_trace_task_completion(t, forced);
+
+        TRACE_TASK(t, "job_completion().\n");
+
+        /* set flags */
+        set_rt_flags(t, RT_F_SLEEP);
+        /* prepare for next period */
+        prepare_for_next_period(t);
+        if (is_released(t, litmus_clock()))
+                sched_trace_task_release(t);
+        /* unlink */
+        unlink(t);
+        /* requeue
+         * But don't requeue a blocking task. */
+        if (is_running(t))
+                gedf_job_arrival(t);
+}
+
+/* gedf_tick - this function is called for every local timer
+ *                         interrupt.
+ *
+ *                   checks whether the current task has expired and checks
+ *                   whether we need to preempt it if it has not expired
+ */
+static void gedf_tick(struct task_struct* t)
+{
+        if (is_realtime(t) && budget_exhausted(t)) {
+                set_tsk_need_resched(t);
+                set_will_schedule();
+        }
+}
+
+static struct task_struct* gedf_schedule(struct task_struct * prev)
+{
+        cpu_entry_t* entry = &__get_cpu_var(gedf_cpu_entries);
+        int out_of_time, sleep, preempt, np, exists, blocks;
+        struct task_struct* next = NULL;
+
+        /* Will be released in finish_switch. */
+        spin_lock(&gedf_lock);
+        clear_will_schedule();
+
+        /* sanity checking */
+        BUG_ON(entry->scheduled && entry->scheduled != prev);
+        BUG_ON(entry->scheduled && !is_realtime(prev));
+        BUG_ON(is_realtime(prev) && !entry->scheduled);
+
+        /* (0) Determine state */
+        exists      = entry->scheduled != NULL;
+        blocks      = exists && !is_running(entry->scheduled);
+        out_of_time = exists && budget_exhausted(entry->scheduled);
+        sleep       = exists && get_rt_flags(entry->scheduled) == RT_F_SLEEP;
+        preempt     = entry->scheduled != entry->linked;
+
+        TRACE_TASK(prev, "invoked gedf_schedule.\n");
+
+        if (exists)
+                TRACE_TASK(prev,
+                           "blocks:%d out_of_time:%d sleep:%d preempt:%d "
+                           "state:%d sig:%d\n",
+                           blocks, out_of_time, sleep, preempt,
+                           prev->state, signal_pending(prev));
+        if (entry->linked && preempt)
+                TRACE_TASK(prev, "will be preempted by %s/%d\n",
+                           entry->linked->comm, entry->linked->pid);
+
+
+        /* If a task blocks we have no choice but to reschedule.
+         */
+        if (blocks)
+                unlink(entry->scheduled);
+
+
+        /* Any task that is preemptable and either exhausts its execution
+         * budget or wants to sleep completes. We may have to reschedule after
+         * this. Don't do a job completion if we block (can't have timers running
+         * for blocked jobs). Preemption go first for the same reason.
+         */
+        if ((out_of_time || sleep) && !blocks && !preempt)
+                job_completion(entry->scheduled, !sleep);
+
+        /* Link pending task if we became unlinked.
+         */
+        if (!entry->linked)
+                link_task_to_cpu(__take_ready(&gedf), entry);
+
+        /* The final scheduling decision. Do we need to switch for some reason?
+         * If linked is different from scheduled, then select linked as next.
+         */
+        if (entry->linked != entry->scheduled) {
+                /* Schedule a linked job? */
+                if (entry->linked) {
+                        entry->linked->rt_param.scheduled_on = entry->cpu;
+                        next = entry->linked;
+                }
+                if (entry->scheduled) {
+                        /* not gonna be scheduled soon */
+                        entry->scheduled->rt_param.scheduled_on = NO_CPU;
+                        TRACE_TASK(entry->scheduled, "scheduled_on = NO_CPU\n");
+                }
+        } else
+                /* Only override Linux scheduler if we have a real-time task
+                 * scheduled that needs to continue.
+                 */
+                if (exists)
+                        next = prev;
+
+        spin_unlock(&gedf_lock);
+
+        TRACE("gedf_lock released, next=0x%p\n", next);
+
+
+        if (next)
+                TRACE_TASK(next, "scheduled at %llu\n", litmus_clock());
+        else if (exists && !next)
+                TRACE("becomes idle at %llu.\n", litmus_clock());
+
+
+        return next;
+}
+
+
+/* _finish_switch - we just finished the switch away from prev
+ */
+static void gedf_finish_switch(struct task_struct *prev)
+{
+        cpu_entry_t*    entry = &__get_cpu_var(gedf_cpu_entries);
+
+        entry->scheduled = is_realtime(current) ? current : NULL;
+        TRACE_TASK(prev, "switched away from\n");
+}
+
+
+/*      Prepare a task for running in RT mode
+ */
+static void gedf_task_new(struct task_struct * t, int on_rq, int running)
+{
+        unsigned long           flags;
+        cpu_entry_t*            entry;
+
+        TRACE("gsn edf: task new %d\n", t->pid);
+
+        spin_lock_irqsave(&gedf_lock, flags);
+        if (running) {
+                entry = &per_cpu(gedf_cpu_entries, task_cpu(t));
+                BUG_ON(entry->scheduled);
+                entry->scheduled = t;
+                t->rt_param.scheduled_on = task_cpu(t);
+        } else
+                t->rt_param.scheduled_on = NO_CPU;
+        t->rt_param.linked_on          = NO_CPU;
+
+        /* setup job params */
+        release_at(t, litmus_clock());
+
+        gedf_job_arrival(t);
+        spin_unlock_irqrestore(&gedf_lock, flags);
+}
+
+static void gedf_task_wake_up(struct task_struct *task)
+{
+        unsigned long flags;
+        lt_t now;
+
+        TRACE_TASK(task, "wake_up at %llu\n", litmus_clock());
+
+        spin_lock_irqsave(&gedf_lock, flags);
+        /* We need to take suspensions because of semaphores into
+         * account! If a job resumes after being suspended due to acquiring
+         * a semaphore, it should never be treated as a new job release.
+         */
+        if (get_rt_flags(task) == RT_F_EXIT_SEM) {
+                set_rt_flags(task, RT_F_RUNNING);
+        } else {
+                now = litmus_clock();
+                if (is_tardy(task, now)) {
+                        /* new sporadic release */
+                        release_at(task, now);
+                        sched_trace_task_release(task);
+                }
+                else if (task->time_slice)
+                        /* came back in time before deadline
+                         */
+                        set_rt_flags(task, RT_F_RUNNING);
+        }
+        gedf_job_arrival(task);
+        spin_unlock_irqrestore(&gedf_lock, flags);
+}
+
+static void gedf_task_block(struct task_struct *t)
+{
+        unsigned long flags;
+
+        TRACE_TASK(t, "block at %llu\n", litmus_clock());
+
+        /* unlink if necessary */
+        spin_lock_irqsave(&gedf_lock, flags);
+        unlink(t);
+        spin_unlock_irqrestore(&gedf_lock, flags);
+
+        BUG_ON(!is_realtime(t));
+}
+
+
+static void gedf_task_exit(struct task_struct * t)
+{
+        unsigned long flags;
+
+        /* unlink if necessary */
+        spin_lock_irqsave(&gedf_lock, flags);
+        unlink(t);
+        if (tsk_rt(t)->scheduled_on != NO_CPU) {
+                gedf_cpus[tsk_rt(t)->scheduled_on]->scheduled = NULL;
+                tsk_rt(t)->scheduled_on = NO_CPU;
+        }
+        spin_unlock_irqrestore(&gedf_lock, flags);
+
+        BUG_ON(!is_realtime(t));
+        TRACE_TASK(t, "RIP\n");
+}
+
+static long gedf_admit_task(struct task_struct* tsk)
+{
+        return 0;
+}
+
+
+/*      Plugin object   */
+static struct sched_plugin gedf_plugin __cacheline_aligned_in_smp = {
+        .plugin_name            = "G-EDF",
+        .finish_switch          = gedf_finish_switch,
+        .tick                   = gedf_tick,
+        .task_new               = gedf_task_new,
+        .complete_job           = complete_job,
+        .task_exit              = gedf_task_exit,
+        .schedule               = gedf_schedule,
+        .task_wake_up           = gedf_task_wake_up,
+        .task_block             = gedf_task_block,
+        .admit_task             = gedf_admit_task
+};
+
+
+static int __init init_gedf(void)
+{
+        int cpu;
+        cpu_entry_t *entry;
+
+        heap_init(&gedf_cpu_heap);
+        /* initialize CPU state */
+        for (cpu = 0; cpu < NR_CPUS; cpu++)  {
+                entry = &per_cpu(gedf_cpu_entries, cpu);
+                gedf_cpus[cpu] = entry;
+                atomic_set(&entry->will_schedule, 0);
+                entry->linked    = NULL;
+                entry->scheduled = NULL;
+                entry->cpu       = cpu;
+                entry->hn        = &gedf_heap_node[cpu];
+                heap_node_init(&entry->hn, entry);
+        }
+        edf_domain_init(&gedf, NULL, gedf_release_jobs);
+        return register_sched_plugin(&gedf_plugin);
+}
+
+
+module_init(init_gedf);