Add EDF-WM plugin

[semi-part backport]

3 files changed, 840 insertions, 1 deletions

diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index a7a183f34a80..9927b09e0a01 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -1,3 +1,5 @@
+#include <linux/threads.h>
+
 /*
  * Definition of the scheduler plugin interface.
  *
@@ -33,6 +35,36 @@ typedef enum {
         PRECISE_ENFORCEMENT  /* NOT IMPLEMENTED - enforced with hrtimers */
 } budget_policy_t;
 
+/* The parameters for the EDF-WM semi-partitioned scheduler.
+ * Each task may be split across multiple cpus. Each per-cpu allocation
+ * is called a 'slice'.
+ */
+#define MAX_EDF_WM_SLICES 24
+#define MIN_EDF_WM_SLICE_SIZE 50000 /* .05 millisecond = 50us */
+
+struct edf_wm_slice {
+        /* on which CPU is this slice allocated */
+        unsigned int cpu;
+        /* relative deadline from job release (not from slice release!) */
+        lt_t deadline;
+        /* budget of this slice; must be precisely enforced */
+        lt_t budget;
+        /* offset of this slice relative to the job release */
+        lt_t offset;
+};
+
+/* If a job is not sliced across multiple CPUs, then
+ * count is set to zero and none of the slices is used.
+ * This implies that count == 1 is illegal.
+ */
+struct edf_wm_params {
+        /* enumeration of all slices */
+        struct edf_wm_slice slices[MAX_EDF_WM_SLICES];
+
+        /* how many slices are defined? */
+        unsigned int count;
+};
+
 struct rt_task {
         lt_t            exec_cost;
         lt_t            period;
@@ -40,6 +72,12 @@ struct rt_task {
         unsigned int    cpu;
         task_class_t    cls;
         budget_policy_t budget_policy; /* ignored by pfair */
+
+        /* parameters used by the semi-partitioned algorithms */
+        union {
+                /* EDF-WM; defined in sched_edf_wm.c */
+                struct edf_wm_params wm;
+        } semi_part;
 };
 
 /* The definition of the data that is shared between the kernel and real-time
@@ -184,6 +222,21 @@ struct rt_param {
 
         /* Pointer to the page shared between userspace and kernel. */
         struct control_page * ctrl_page;
+
+        /* runtime info for the semi-part plugins */
+        union {
+                /* EDF-WM runtime information */
+                struct {
+                        /* at which exec time did the current slice start? */
+                        lt_t exec_time;
+                        /* when did the job suspend? */
+                        lt_t suspend_time;
+                        /* cached job parameters */
+                        lt_t job_release, job_deadline;
+                        /* pointer to the current slice */
+                        struct edf_wm_slice* slice;
+                } wm;
+        } semi_part;
 };
 
 /*      Possible RT flags       */
diff --git a/litmus/Makefile b/litmus/Makefile
index f301d2842e43..7fe37a59c425 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -14,7 +14,8 @@ obj-y     = sched_plugin.o litmus.o \
             bheap.o \
             ctrldev.o \
             sched_gsn_edf.o \
-            sched_psn_edf.o
+            sched_psn_edf.o \
+            sched_edf_wm.o
 
 obj-$(CONFIG_PLUGIN_CEDF) += sched_cedf.o
 obj-$(CONFIG_PLUGIN_PFAIR) += sched_pfair.o
diff --git a/litmus/sched_edf_wm.c b/litmus/sched_edf_wm.c
new file mode 100644
index 000000000000..f4219ca812d3
--- /dev/null
+++ b/litmus/sched_edf_wm.c
@@ -0,0 +1,785 @@
+/* EDF-WM: based on PSN-EDF.
+ */
+
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
+#include <linux/module.h>
+
+#include <litmus/litmus.h>
+#include <litmus/jobs.h>
+#include <litmus/sched_plugin.h>
+#include <litmus/edf_common.h>
+
+typedef struct {
+        rt_domain_t             domain;
+        int                     cpu;
+        struct task_struct*     scheduled; /* only RT tasks */
+
+        /* The enforcement timer is used to accurately police
+         * slice budgets. */
+        struct hrtimer          enforcement_timer;
+        int                     timer_armed;
+/*
+ * scheduling lock slock
+ * protects the domain and serializes scheduling decisions
+ */
+#define slock domain.ready_lock
+
+} wm_domain_t;
+
+DEFINE_PER_CPU(wm_domain_t, wm_domains);
+
+#define TRACE_DOM(dom, fmt, args...) \
+        TRACE("(wm_domains[%d]) " fmt, (dom)->cpu, ##args)
+
+
+#define local_domain         (&__get_cpu_var(wm_domains))
+#define remote_domain(cpu)   (&per_cpu(wm_domains, cpu))
+#define domain_of_task(task) (remote_domain(get_partition(task)))
+#define domain_from_timer(t) (container_of((t), wm_domain_t, enforcement_timer))
+
+static int is_sliced_task(struct task_struct* t)
+{
+        return tsk_rt(t)->task_params.semi_part.wm.count;
+}
+
+static struct edf_wm_slice* get_last_slice(struct task_struct* t)
+{
+        int idx = tsk_rt(t)->task_params.semi_part.wm.count - 1;
+        return tsk_rt(t)->task_params.semi_part.wm.slices + idx;
+}
+
+static void compute_slice_params(struct task_struct* t)
+{
+        struct rt_param* p = tsk_rt(t);
+        /* Here we do a little trick to make the generic EDF code
+         * play well with job slices. We overwrite the job-level
+         * release and deadline fields with the slice-specific values
+         * so that we can enqueue this task in an EDF rt_domain_t
+         * without issue. The actual values are cached in the semi_part.wm
+         * structure. */
+        p->job_params.deadline = p->semi_part.wm.job_release +
+                p->semi_part.wm.slice->deadline;
+        p->job_params.release  = p->semi_part.wm.job_release +
+                p->semi_part.wm.slice->offset;
+
+        /* Similarly, we play a trick on the cpu field. */
+        p->task_params.cpu = p->semi_part.wm.slice->cpu;
+
+        /* update the per-slice budget reference */
+        p->semi_part.wm.exec_time = p->job_params.exec_time;
+}
+
+static void complete_sliced_job(struct task_struct* t)
+{
+        struct rt_param* p = tsk_rt(t);
+
+        /* We need to undo our trickery to the
+         * job parameters (see above). */
+        p->job_params.release  = p->semi_part.wm.job_release;
+        p->job_params.deadline = p->semi_part.wm.job_deadline;
+
+        /* Ok, now let generic code do the actual work. */
+        prepare_for_next_period(t);
+
+        /* And finally cache the updated parameters. */
+        p->semi_part.wm.job_release = p->job_params.release;
+        p->semi_part.wm.job_deadline = p->job_params.deadline;
+}
+
+static lt_t slice_exec_time(struct task_struct* t)
+{
+        struct rt_param* p = tsk_rt(t);
+
+        /* Compute how much execution time has been consumed
+         * since last slice advancement. */
+        return p->job_params.exec_time - p->semi_part.wm.exec_time;
+}
+
+static lt_t slice_budget(struct task_struct* t)
+{
+        return tsk_rt(t)->semi_part.wm.slice->budget;
+}
+
+static int slice_budget_exhausted(struct task_struct* t)
+{
+        return slice_exec_time(t) >= slice_budget(t);
+}
+
+/* assumes positive remainder; overflows otherwise */
+static lt_t slice_budget_remaining(struct task_struct* t)
+{
+        return slice_budget(t) - slice_exec_time(t);
+}
+
+static lt_t wm_budget_remaining(struct task_struct* t)
+{
+        if (is_sliced_task(t))
+                return slice_budget_remaining(t);
+        else
+                return budget_remaining(t);
+}
+
+static int wm_budget_exhausted(struct task_struct* t)
+{
+        if (is_sliced_task(t))
+                return slice_budget_exhausted(t);
+        else
+                return budget_exhausted(t);
+}
+
+static void advance_next_slice(struct task_struct* t, int completion_signaled)
+{
+        int idx;
+        struct rt_param* p = tsk_rt(t);
+
+        /* make sure this is actually a sliced job */
+        BUG_ON(!is_sliced_task(t));
+        BUG_ON(is_queued(t));
+
+        /* determine index of current slice */
+        idx = p->semi_part.wm.slice -
+                p->task_params.semi_part.wm.slices;
+
+        TRACE_TASK(t, "advancing slice %d; excess=%lluns; "
+                   "completion_signaled=%d.\n",
+                   idx, slice_exec_time(t) - slice_budget(t),
+                   completion_signaled);
+
+        if (completion_signaled)
+                idx = 0;
+        else
+                /* increment and wrap around, if necessary */
+                idx = (idx + 1) % p->task_params.semi_part.wm.count;
+
+        /* point to next slice */
+        p->semi_part.wm.slice =
+                p->task_params.semi_part.wm.slices + idx;
+
+        /* Check if we need to update essential job parameters. */
+        if (!idx) {
+                /* job completion */
+                sched_trace_task_completion(t, !completion_signaled);
+                TRACE_TASK(t, "completed sliced job"
+                           "(signaled:%d)\n", completion_signaled);
+                complete_sliced_job(t);
+        }
+
+        /* Update job parameters for new slice. */
+        compute_slice_params(t);
+}
+
+/* assumes time_passed does not advance past the last slice */
+static void fast_forward_slices(struct task_struct* t, lt_t time_passed)
+{
+        TRACE_TASK(t, "fast forwarding %lluns\n", time_passed);
+
+        /* this is NOT the slice version */
+        BUG_ON(budget_remaining(t) <= time_passed);
+
+        if (wm_budget_exhausted(t)) {
+                /* This can happen if a suspension raced
+                 * with a normal slice advancement. wm_schedule()
+                 * does not process out_of_time when a task blocks. */
+                TRACE_TASK(t, "block raced with out_of_time?\n");
+                advance_next_slice(t, 0);
+        }
+
+        while (time_passed &&
+               time_passed >= slice_budget_remaining(t)) {
+                /* slice completely exhausted */
+                time_passed -= slice_budget_remaining(t);
+                tsk_rt(t)->job_params.exec_time +=
+                        slice_budget_remaining(t);
+
+                BUG_ON(!slice_budget_exhausted(t));
+                BUG_ON(slice_budget_remaining(t) != 0);
+                BUG_ON(tsk_rt(t)->semi_part.wm.slice == get_last_slice(t));
+
+                advance_next_slice(t, 0);
+        }
+        /* add remainder to exec cost */
+        tsk_rt(t)->job_params.exec_time += time_passed;
+}
+
+/* we assume the lock is being held */
+static void preempt(wm_domain_t *dom)
+{
+        TRACE_DOM(dom, "will be preempted.\n");
+        /* We pass NULL as the task since non-preemptive sections are not
+         * supported in this plugin, so per-task checks are not needed. */
+        preempt_if_preemptable(NULL, dom->cpu);
+}
+
+static enum hrtimer_restart on_enforcement_timeout(struct hrtimer *timer)
+{
+        wm_domain_t *dom = domain_from_timer(timer);
+        unsigned long flags;
+
+        raw_spin_lock_irqsave(&dom->slock, flags);
+        if (likely(dom->timer_armed)) {
+                TRACE_DOM(dom, "enforcement timer fired.\n");
+                dom->timer_armed = 0;
+                preempt(dom);
+        } else
+                TRACE_DOM(dom, "timer fired but not armed???\n");
+        raw_spin_unlock_irqrestore(&dom->slock, flags);
+        return  HRTIMER_NORESTART;
+}
+
+/* assumes called with IRQs off */
+static void cancel_enforcement_timer(wm_domain_t* dom)
+{
+        int ret;
+
+        TRACE_DOM(dom, "cancelling enforcement timer.\n");
+
+        /* Arming the timer makes only sense locally. */
+        BUG_ON(dom->cpu != raw_smp_processor_id());
+
+        /* Since interrupts are disabled and and dom->timer_armed is only
+         * modified locally, we do not need to lock this domain.
+         */
+
+        if (dom->timer_armed) {
+                ret = hrtimer_try_to_cancel(&dom->enforcement_timer);
+                /* Should never be inactive. */
+                BUG_ON(ret == 0);
+                /* Should never be running concurrently. */
+                BUG_ON(ret == -1);
+
+                dom->timer_armed = 0;
+        }
+}
+
+/* assumes called with IRQs off */
+static void arm_enforcement_timer(wm_domain_t* dom, struct task_struct* t)
+{
+        lt_t when_to_fire;
+
+        TRACE_DOM(dom, "arming enforcement timer.\n");
+
+        /* The task has to belong to this domain. */
+        BUG_ON(domain_of_task(t) != dom);
+
+        /* Arming the timer makes only sense locally. */
+        BUG_ON(dom->cpu != raw_smp_processor_id());
+
+        /* Calling this when there is no budget left for the task
+         * makes no sense. */
+        BUG_ON(wm_budget_exhausted(t));
+
+        /* __hrtimer_start_range_ns() cancels the timer
+         * anyway, so we don't have to check whether it is still armed
+         */
+
+        when_to_fire = litmus_clock() + wm_budget_remaining(t);
+        __hrtimer_start_range_ns(&dom->enforcement_timer,
+                                 ns_to_ktime(when_to_fire),
+                                 0 /* delta */,
+                                 HRTIMER_MODE_ABS_PINNED,
+                                 0 /* no wakeup */);
+
+        dom->timer_armed = 1;
+}
+
+static void wm_domain_init(wm_domain_t* dom,
+                           check_resched_needed_t check,
+                           release_jobs_t release,
+                           int cpu)
+{
+        edf_domain_init(&dom->domain, check, release);
+        dom->cpu                = cpu;
+        dom->scheduled          = NULL;
+        dom->timer_armed        = 0;
+        hrtimer_init(&dom->enforcement_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+        dom->enforcement_timer.function = on_enforcement_timeout;
+}
+
+static void wm_requeue_remote(struct task_struct *t)
+{
+        wm_domain_t *dom = domain_of_task(t);
+
+        set_rt_flags(t, RT_F_RUNNING);
+        if (is_released(t, litmus_clock()))
+                /* acquires necessary lock */
+                add_ready(&dom->domain, t);
+        else
+                /* force timer on remote CPU */
+                add_release_on(&dom->domain, t, get_partition(t));
+}
+
+static void wm_requeue_local(struct task_struct* t, rt_domain_t *edf)
+{
+        if (t->state != TASK_RUNNING)
+                TRACE_TASK(t, "requeue: !TASK_RUNNING\n");
+
+        set_rt_flags(t, RT_F_RUNNING);
+        if (is_released(t, litmus_clock()))
+                __add_ready(edf, t);
+        else
+                add_release(edf, t); /* it has got to wait */
+}
+
+static int wm_check_resched(rt_domain_t *edf)
+{
+        wm_domain_t *dom = container_of(edf, wm_domain_t, domain);
+
+        /* because this is a callback from rt_domain_t we already hold
+         * the necessary lock for the ready queue
+         */
+        if (edf_preemption_needed(edf, dom->scheduled)) {
+                preempt(dom);
+                return 1;
+        } else
+                return 0;
+}
+
+static void regular_job_completion(struct task_struct* t, int forced)
+{
+        sched_trace_task_completion(t, forced);
+        TRACE_TASK(t, "job_completion().\n");
+
+        set_rt_flags(t, RT_F_SLEEP);
+        prepare_for_next_period(t);
+}
+
+static void wm_job_or_slice_completion(struct task_struct* t,
+                                       int completion_signaled)
+{
+        if (is_sliced_task(t))
+                advance_next_slice(t, completion_signaled);
+        else
+                regular_job_completion(t, !completion_signaled);
+}
+
+static void wm_tick(struct task_struct *t)
+{
+        wm_domain_t *dom = local_domain;
+
+        /* Check for inconsistency. We don't need the lock for this since
+         * ->scheduled is only changed in schedule, which obviously is not
+         *  executing in parallel on this CPU
+         */
+        BUG_ON(is_realtime(t) && t != dom->scheduled);
+
+        if (is_realtime(t) && budget_enforced(t) && wm_budget_exhausted(t)) {
+                set_tsk_need_resched(t);
+                TRACE_DOM(dom, "budget of %d exhausted in tick\n",
+                          t->pid);
+        }
+}
+
+static struct task_struct* wm_schedule(struct task_struct * prev)
+{
+        wm_domain_t             *dom = local_domain;
+        rt_domain_t             *edf = &dom->domain;
+        struct task_struct      *next, *migrate = NULL;
+
+        int out_of_time, sleep, preempt, wrong_cpu, exists, blocks, resched;
+
+        raw_spin_lock(&dom->slock);
+
+        /* Sanity checking:
+         * When a task exits (dead) dom->schedule may be null
+         * and prev _is_ realtime. */
+        BUG_ON(dom->scheduled && dom->scheduled != prev);
+        BUG_ON(dom->scheduled && !is_realtime(prev));
+
+        /* (0) Determine state */
+        exists      = dom->scheduled != NULL;
+        wrong_cpu   = exists && get_partition(dom->scheduled) != dom->cpu;
+        blocks      = exists && !is_running(dom->scheduled);
+        out_of_time = exists
+                && budget_enforced(dom->scheduled)
+                && wm_budget_exhausted(dom->scheduled);
+        sleep       = exists && get_rt_flags(dom->scheduled) == RT_F_SLEEP;
+        preempt     = edf_preemption_needed(edf, prev);
+
+        /* If we need to preempt do so.
+         * The following checks set resched to 1 in case of special
+         * circumstances.
+         */
+        resched = preempt;
+
+
+        if (exists)
+                TRACE_TASK(prev,
+                           "blocks:%d out_of_time:%d sleep:%d preempt:%d "
+                           "wrong_cpu:%d state:%d sig:%d\n",
+                           blocks, out_of_time, sleep, preempt, wrong_cpu,
+                           prev->state, signal_pending(prev));
+
+        /* If a task blocks we have no choice but to reschedule.
+         */
+        if (blocks)
+                resched = 1;
+
+        /* This can happen if sliced task was moved to the next slice
+         * by the wake_up() code path while still being scheduled.
+         */
+        if (wrong_cpu)
+                resched = 1;
+
+        /* Any task that is preemptable and either exhausts its execution
+         * budget or wants to sleep completes. We may have to reschedule after
+         * this.
+         */
+        if ((out_of_time || sleep) && !blocks) {
+                wm_job_or_slice_completion(dom->scheduled, sleep);
+                resched = 1;
+        }
+
+        /* The final scheduling decision. Do we need to switch for some reason?
+         * Switch if we are in RT mode and have no task or if we need to
+         * resched.
+         */
+        next = NULL;
+        if (resched || !exists) {
+                if (dom->scheduled && !blocks) {
+                        if (get_partition(dom->scheduled) == dom->cpu)
+                                /* local task */
+                                wm_requeue_local(dom->scheduled, edf);
+                        else
+                                /* not local anymore; wait until we drop the
+                                 * ready queue lock */
+                                migrate = dom->scheduled;
+                }
+                next = __take_ready(edf);
+        } else
+                /* Only override Linux scheduler if we have a real-time task
+                 * scheduled that needs to continue. */
+                if (exists)
+                        next = prev;
+
+        if (next) {
+                TRACE_TASK(next, "scheduled at %llu (state:%d/%d)\n", litmus_clock(),
+                           next->state, is_running(next));
+                set_rt_flags(next, RT_F_RUNNING);
+        } else if (exists) {
+                TRACE("becoming idle at %llu\n", litmus_clock());
+        }
+
+        dom->scheduled = next;
+        raw_spin_unlock(&dom->slock);
+
+        /* check if we need to push the previous task onto another queue */
+        if (migrate) {
+                TRACE_TASK(migrate, "schedule-initiated migration to %d\n",
+                           get_partition(migrate));
+                wm_requeue_remote(migrate);
+        }
+
+        if (next && budget_precisely_enforced(next)) {
+                /* Make sure we call into the scheduler when this budget
+                 * expires. */
+                arm_enforcement_timer(dom, next);
+        } else if (dom->timer_armed) {
+                /* Make sure we don't cause unnecessary interrupts. */
+                cancel_enforcement_timer(dom);
+        }
+
+        return next;
+}
+
+
+/*      Prepare a task for running in RT mode
+ */
+static void wm_task_new(struct task_struct * t, int on_rq, int running)
+{
+        wm_domain_t* dom = domain_of_task(t);
+        rt_domain_t* edf = &dom->domain;
+        unsigned long flags;
+
+        TRACE_TASK(t, "edf-wm: task new, cpu = %d\n",
+                   t->rt_param.task_params.cpu);
+
+        /* setup job parameters */
+        release_at(t, litmus_clock());
+
+        /* The task should be running in the queue, otherwise signal
+         * code will try to wake it up with fatal consequences.
+         */
+        raw_spin_lock_irqsave(&dom->slock, flags);
+
+        if (is_sliced_task(t)) {
+                /* make sure parameters are initialized consistently */
+                tsk_rt(t)->semi_part.wm.exec_time = 0;
+                tsk_rt(t)->semi_part.wm.job_release  = get_release(t);
+                tsk_rt(t)->semi_part.wm.job_deadline = get_deadline(t);
+                tsk_rt(t)->semi_part.wm.slice = tsk_rt(t)->task_params.semi_part.wm.slices;
+                tsk_rt(t)->job_params.exec_time = 0;
+        }
+
+        if (running) {
+                /* there shouldn't be anything else running at the time */
+                BUG_ON(dom->scheduled);
+                dom->scheduled = t;
+        } else {
+                wm_requeue_local(t, edf);
+                /* maybe we have to reschedule */
+                preempt(dom);
+        }
+        raw_spin_unlock_irqrestore(&dom->slock, flags);
+}
+
+static void wm_release_at(struct task_struct *t, lt_t start)
+{
+        struct rt_param* p = tsk_rt(t);
+
+        if (is_sliced_task(t)) {
+                /* simulate wrapping to the first slice */
+                p->semi_part.wm.job_deadline = start;
+                p->semi_part.wm.slice = get_last_slice(t);
+                /* FIXME: creates bogus completion event... */
+                advance_next_slice(t, 0);
+                set_rt_flags(t, RT_F_RUNNING);
+        } else
+                /* generic code handles it */
+                release_at(t, start);
+}
+
+static lt_t wm_earliest_release(struct task_struct *t, lt_t now)
+{
+        lt_t deadline;
+        if (is_sliced_task(t))
+                deadline = tsk_rt(t)->semi_part.wm.job_deadline;
+        else
+                deadline = get_deadline(t);
+        if (lt_before(deadline, now))
+                return now;
+        else
+                return deadline;
+}
+
+static void wm_task_wake_up(struct task_struct *t)
+{
+        unsigned long flags;
+        wm_domain_t* dom = domain_of_task(t);
+        rt_domain_t* edf = &dom->domain;
+        struct rt_param* p = tsk_rt(t);
+        lt_t now, sleep_time;
+        int migrate = 0;
+
+        raw_spin_lock_irqsave(&dom->slock, flags);
+        BUG_ON(is_queued(t));
+
+        now = litmus_clock();
+
+        sleep_time = now - p->semi_part.wm.suspend_time;
+
+        TRACE_TASK(t, "wake_up at %llu after %llu, still-scheduled:%d\n",
+                   now, sleep_time, dom->scheduled == t);
+
+        /* account sleep time as execution time */
+        if (get_exec_time(t) + sleep_time >= get_exec_cost(t)) {
+                /* new sporadic release */
+                TRACE_TASK(t, "new sporadic release\n");
+                wm_release_at(t, wm_earliest_release(t, now));
+                sched_trace_task_release(t);
+        } else if (is_sliced_task(t)) {
+                /* figure out which slice we should be executing on */
+                fast_forward_slices(t, sleep_time);
+                /* can't be exhausted now */
+                BUG_ON(wm_budget_exhausted(t));
+        } else {
+                /* simply add to the execution time */
+                tsk_rt(t)->job_params.exec_time += sleep_time;
+        }
+
+
+        /* Only add to ready queue if it is not the currently-scheduled
+         * task. This could be the case if a task was woken up concurrently
+         * on a remote CPU before the executing CPU got around to actually
+         * de-scheduling the task, i.e., wake_up() raced with schedule()
+         * and won.
+         */
+        if (dom->scheduled != t) {
+                if (get_partition(t) == dom->cpu)
+                        wm_requeue_local(t, edf);
+                else
+                        /* post-pone migration until after unlocking */
+                        migrate = 1;
+        }
+
+        raw_spin_unlock_irqrestore(&dom->slock, flags);
+
+        if (migrate) {
+                TRACE_TASK(t, "wake_up-initiated migration to %d\n",
+                           get_partition(t));
+                wm_requeue_remote(t);
+        }
+
+        TRACE_TASK(t, "wake up done\n");
+}
+
+static void wm_task_block(struct task_struct *t)
+{
+        wm_domain_t* dom = domain_of_task(t);
+        unsigned long flags;
+        lt_t now = litmus_clock();
+
+        TRACE_TASK(t, "block at %llu, state=%d\n", now, t->state);
+
+        tsk_rt(t)->semi_part.wm.suspend_time = now;
+
+        raw_spin_lock_irqsave(&dom->slock, flags);
+        if (is_queued(t)) {
+                TRACE_TASK(t, "still queued; migration invariant failed?\n");
+                remove(&dom->domain, t);
+        }
+        raw_spin_unlock_irqrestore(&dom->slock, flags);
+
+        BUG_ON(!is_realtime(t));
+}
+
+static void wm_task_exit(struct task_struct * t)
+{
+        unsigned long flags;
+        wm_domain_t* dom = domain_of_task(t);
+        rt_domain_t* edf = &dom->domain;
+
+        raw_spin_lock_irqsave(&dom->slock, flags);
+        if (is_queued(t)) {
+                /* dequeue */
+                remove(edf, t);
+        }
+        if (dom->scheduled == t)
+                dom->scheduled = NULL;
+
+        TRACE_TASK(t, "RIP, now reschedule\n");
+
+        preempt(dom);
+        raw_spin_unlock_irqrestore(&dom->slock, flags);
+}
+
+static long wm_check_params(struct task_struct *t)
+{
+        struct rt_param* p = tsk_rt(t);
+        struct edf_wm_params* wm = &p->task_params.semi_part.wm;
+        int i;
+        lt_t tmp;
+
+        if (!is_sliced_task(t)) {
+                /* regular task; nothing to check */
+                TRACE_TASK(t, "accepted regular (non-sliced) task with "
+                           "%d slices\n",
+                           wm->count);
+                return 0;
+        }
+
+        /* (1) Either not sliced, or more than 1 slice. */
+        if (wm->count == 1 || wm->count > MAX_EDF_WM_SLICES) {
+                TRACE_TASK(t, "bad number of slices (%u) \n",
+                           wm->count);
+                return -EINVAL;
+        }
+
+        /* (2) The partition has to agree with the first slice. */
+        if (get_partition(t) != wm->slices[0].cpu) {
+                TRACE_TASK(t, "partition and first slice CPU differ "
+                           "(%d != %d)\n", get_partition(t), wm->slices[0].cpu);
+                return -EINVAL;
+        }
+
+        /* (3) The total budget must agree. */
+        for (i = 0, tmp = 0; i < wm->count; i++)
+                tmp += wm->slices[i].budget;
+        if (get_exec_cost(t) != tmp) {
+                TRACE_TASK(t, "total budget and sum of slice budgets differ\n");
+                return -EINVAL;
+        }
+
+        /* (4) The release of each slice must not precede the previous
+         *     deadline. */
+        for (i = 0; i < wm->count - 1; i++)
+                if (wm->slices[i].deadline > wm->slices[i + 1].offset) {
+                        TRACE_TASK(t, "slice %d overlaps with slice %d\n",
+                                   i, i + 1);
+                        return -EINVAL;
+                }
+
+        /* (5) The budget of each slice must fit within [offset, deadline] */
+        for (i = 0; i < wm->count; i++)
+                if (lt_before(wm->slices[i].deadline, wm->slices[i].offset) ||
+                    wm->slices[i].deadline - wm->slices[i].offset <
+                    wm->slices[i].budget) {
+                        TRACE_TASK(t, "slice %d is overloaded\n", i);
+                        return -EINVAL;
+                }
+
+        /* (6) The budget of each slice must exceed the minimum budget size. */
+        for (i = 0; i < wm->count; i++)
+                if (wm->slices[i].budget < MIN_EDF_WM_SLICE_SIZE) {
+                        TRACE_TASK(t, "slice %d is too short\n", i);
+                        return -EINVAL;
+                }
+
+        /* (7) The CPU of each slice must be different from the previous CPU. */
+        for (i = 0; i < wm->count - 1; i++)
+                if (wm->slices[i].cpu == wm->slices[i + 1].cpu) {
+                        TRACE_TASK(t, "slice %d does not migrate\n", i);
+                        return -EINVAL;
+                }
+
+        /* (8) The CPU of each slice must be online. */
+        for (i = 0; i < wm->count; i++)
+                if (!cpu_online(wm->slices[i].cpu)) {
+                        TRACE_TASK(t, "slice %d is allocated on offline CPU\n",
+                                   i);
+                        return -EINVAL;
+                }
+
+        /* (9) A sliced task's budget must be precisely enforced. */
+        if (!budget_precisely_enforced(t)) {
+                TRACE_TASK(t, "budget is not precisely enforced "
+                           "(policy: %d).\n",
+                           tsk_rt(t)->task_params.budget_policy);
+                return -EINVAL;
+        }
+
+        TRACE_TASK(t, "accepted sliced task with %d slices\n",
+                   wm->count);
+
+        return 0;
+}
+
+static long wm_admit_task(struct task_struct* t)
+{
+        return task_cpu(t) == get_partition(t) ? wm_check_params(t) : -EINVAL;
+}
+
+/*      Plugin object   */
+static struct sched_plugin edf_wm_plugin __cacheline_aligned_in_smp = {
+        .plugin_name            = "EDF-WM",
+        .tick                   = wm_tick,
+        .task_new               = wm_task_new,
+        .complete_job           = complete_job,
+        .task_exit              = wm_task_exit,
+        .schedule               = wm_schedule,
+        .release_at             = wm_release_at,
+        .task_wake_up           = wm_task_wake_up,
+        .task_block             = wm_task_block,
+        .admit_task             = wm_admit_task
+};
+
+
+static int __init init_edf_wm(void)
+{
+        int i;
+
+        /* FIXME: breaks with CPU hotplug
+         */
+        for (i = 0; i < num_online_cpus(); i++) {
+                wm_domain_init(remote_domain(i),
+                               wm_check_resched,
+                               NULL, i);
+        }
+        return register_sched_plugin(&edf_wm_plugin);
+}
+
+module_init(init_edf_wm);
+