[ported from 2008.3] Core LITMUS^RT infrastructure

Port 2008.3 Core LITMUS^RT infrastructure to Linux 2.6.32

litmus_sched_class implements 4 new methods:

- prio_changed:
  void

- switched_to:
  void

- get_rr_interval:
  return infinity (i.e., 0)

- select_task_rq:
  return current cpu

4 files changed, 93 insertions, 10 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 166b8c49257c..889730cce3ad 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -74,6 +74,9 @@
 
 #include <trace/events/sched.h>
 
+#include <litmus/litmus.h>
+#include <litmus/sched_plugin.h>
+
 /*
  * Protected counters by write_lock_irq(&tasklist_lock)
  */
@@ -162,6 +165,7 @@ void __put_task_struct(struct task_struct *tsk)
         WARN_ON(atomic_read(&tsk->usage));
         WARN_ON(tsk == current);
 
+        exit_litmus(tsk);
         exit_creds(tsk);
         delayacct_tsk_free(tsk);
 
@@ -244,6 +248,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 
         tsk->stack = ti;
 
+        /* Don't let the new task be a real-time task. */
+        memset(&tsk->rt_param, 0, sizeof(struct rt_task));
+
         err = prop_local_init_single(&tsk->dirties);
         if (err)
                 goto out;
diff --git a/kernel/sched.c b/kernel/sched.c
index 3c11ae0a948d..fcaed6b96442 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -77,6 +77,9 @@
 
 #include "sched_cpupri.h"
 
+#include <litmus/sched_trace.h>
+#include <litmus/trace.h>
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/sched.h>
 
@@ -571,6 +574,8 @@ struct rq {
 
         atomic_t nr_iowait;
 
+        struct task_struct *litmus_next;
+
 #ifdef CONFIG_SMP
         struct root_domain *rd;
         struct sched_domain *sd;
@@ -1815,11 +1820,12 @@ static void calc_load_account_active(struct rq *this_rq);
 #include "sched_idletask.c"
 #include "sched_fair.c"
 #include "sched_rt.c"
+#include "../litmus/sched_litmus.c"
 #ifdef CONFIG_SCHED_DEBUG
 # include "sched_debug.c"
 #endif
 
-#define sched_class_highest (&rt_sched_class)
+#define sched_class_highest (&litmus_sched_class)
 #define for_each_class(class) \
    for (class = sched_class_highest; class; class = class->next)
 
@@ -2343,6 +2349,9 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
         unsigned long flags;
         struct rq *rq, *orig_rq;
 
+        if (is_realtime(p))
+                TRACE_TASK(p, "try_to_wake_up() state:%d\n", p->state);
+
         if (!sched_feat(SYNC_WAKEUPS))
                 wake_flags &= ~WF_SYNC;
 
@@ -2361,7 +2370,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
         orig_cpu = cpu;
 
 #ifdef CONFIG_SMP
-        if (unlikely(task_running(rq, p)))
+        if (unlikely(task_running(rq, p)) || is_realtime(p))
                 goto out_activate;
 
         /*
@@ -2442,6 +2451,8 @@ out_running:
                 p->sched_class->task_wake_up(rq, p);
 #endif
 out:
+        if (is_realtime(p))
+                TRACE_TASK(p, "try_to_wake_up() done state:%d\n", p->state);
         task_rq_unlock(rq, &flags);
         put_cpu();
 
@@ -2750,6 +2761,8 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
          */
         prev_state = prev->state;
         finish_arch_switch(prev);
+        litmus->finish_switch(prev);
+        prev->rt_param.stack_in_use = NO_CPU;
         perf_event_task_sched_in(current, cpu_of(rq));
         finish_lock_switch(rq, prev);
 
@@ -5232,18 +5245,31 @@ void scheduler_tick(void)
 
         sched_clock_tick();
 
+        TS_TICK_START(current);
+
         spin_lock(&rq->lock);
         update_rq_clock(rq);
         update_cpu_load(rq);
         curr->sched_class->task_tick(rq, curr, 0);
+
+        /*
+         * LITMUS_TODO: can we move litmus_tick inside task_tick
+         * or will deadlock ?
+         */
+        TS_PLUGIN_TICK_START;
+        litmus_tick(rq, curr);
+        TS_PLUGIN_TICK_END;
+
         spin_unlock(&rq->lock);
 
         perf_event_task_tick(curr, cpu);
 
 #ifdef CONFIG_SMP
         rq->idle_at_tick = idle_cpu(cpu);
-        trigger_load_balance(rq, cpu);
+        if (!is_realtime(current))
+                trigger_load_balance(rq, cpu);
 #endif
+        TS_TICK_END(current);
 }
 
 notrace unsigned long get_parent_ip(unsigned long addr)
@@ -5387,11 +5413,17 @@ pick_next_task(struct rq *rq)
          * Optimization: we know that if all tasks are in
          * the fair class we can call that function directly:
          */
+        /*
+         * LITMUS_TODO: can we move processes out of fair class?
+         * i.e., create a litmus_rq
+         */
+        /* Don't do this for LITMUS
         if (likely(rq->nr_running == rq->cfs.nr_running)) {
                 p = fair_sched_class.pick_next_task(rq);
                 if (likely(p))
                         return p;
         }
+        */
 
         class = sched_class_highest;
         for ( ; ; ) {
@@ -5426,6 +5458,8 @@ need_resched:
 
         release_kernel_lock(prev);
 need_resched_nonpreemptible:
+        TS_SCHED_START;
+        sched_trace_task_switch_away(prev);
 
         schedule_debug(prev);
 
@@ -5436,6 +5470,14 @@ need_resched_nonpreemptible:
         update_rq_clock(rq);
         clear_tsk_need_resched(prev);
 
+        /*
+         * LITMUS_TODO: can we integrate litmus_schedule in
+         * pick_next_task?
+         */
+        TS_PLUGIN_SCHED_START;
+        litmus_schedule(rq, prev);
+        TS_PLUGIN_SCHED_END;
+
         if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
                 if (unlikely(signal_pending_state(prev->state, prev)))
                         prev->state = TASK_RUNNING;
@@ -5460,22 +5502,35 @@ need_resched_nonpreemptible:
                 rq->curr = next;
                 ++*switch_count;
 
+                TS_SCHED_END(next);
+                TS_CXS_START(next);
                 context_switch(rq, prev, next); /* unlocks the rq */
+                TS_CXS_END(current);
                 /*
                  * the context switch might have flipped the stack from under
                  * us, hence refresh the local variables.
                  */
                 cpu = smp_processor_id();
                 rq = cpu_rq(cpu);
-        } else
+        } else {
+                TS_SCHED_END(prev);
                 spin_unlock_irq(&rq->lock);
+        }
+
+        TS_SCHED2_START(current);
+        sched_trace_task_switch_to(current);
 
         post_schedule(rq);
 
-        if (unlikely(reacquire_kernel_lock(current) < 0))
+        if (unlikely(reacquire_kernel_lock(current) < 0)) {
+                TS_SCHED2_END(current);
                 goto need_resched_nonpreemptible;
+        }
 
         preempt_enable_no_resched();
+
+        TS_SCHED2_END(current);
+
         if (need_resched())
                 goto need_resched;
 }
@@ -6185,6 +6240,9 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
         case SCHED_RR:
                 p->sched_class = &rt_sched_class;
                 break;
+        case SCHED_LITMUS:
+                p->sched_class = &litmus_sched_class;
+                break;
         }
 
         p->rt_priority = prio;
@@ -6232,7 +6290,7 @@ recheck:
 
                 if (policy != SCHED_FIFO && policy != SCHED_RR &&
                                 policy != SCHED_NORMAL && policy != SCHED_BATCH &&
-                                policy != SCHED_IDLE)
+                                policy != SCHED_IDLE && policy != SCHED_LITMUS)
                         return -EINVAL;
         }
 
@@ -6247,6 +6305,8 @@ recheck:
                 return -EINVAL;
         if (rt_policy(policy) != (param->sched_priority != 0))
                 return -EINVAL;
+        if (policy == SCHED_LITMUS && policy == p->policy)
+                return -EINVAL;
 
         /*
          * Allow unprivileged RT tasks to decrease priority:
@@ -6301,6 +6361,12 @@ recheck:
                         return retval;
         }
 
+        if (policy == SCHED_LITMUS) {
+                retval = litmus_admit_task(p);
+                if (retval)
+                        return retval;
+        }
+
         /*
          * make sure no PI-waiters arrive (or leave) while we are
          * changing the priority of the task:
@@ -6328,9 +6394,18 @@ recheck:
 
         p->sched_reset_on_fork = reset_on_fork;
 
+        if (p->policy == SCHED_LITMUS)
+                litmus_exit_task(p);
+
         oldprio = p->prio;
         __setscheduler(rq, p, policy, param->sched_priority);
 
+        if (policy == SCHED_LITMUS) {
+                p->rt_param.stack_in_use = running ? rq->cpu : NO_CPU;
+                p->rt_param.present = running;
+                litmus->task_new(p, on_rq, running);
+        }
+
         if (running)
                 p->sched_class->set_curr_task(rq);
         if (on_rq) {
@@ -6500,10 +6575,11 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
         read_lock(&tasklist_lock);
 
         p = find_process_by_pid(pid);
-        if (!p) {
+        /* Don't set affinity if task not found and for LITMUS tasks */
+        if (!p || is_realtime(p)) {
                 read_unlock(&tasklist_lock);
                 put_online_cpus();
-                return -ESRCH;
+                return p ? -EPERM : -ESRCH;
         }
 
         /*
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 37087a7fac22..ef43ff95999d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1598,7 +1598,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
 
         update_curr(cfs_rq);
 
-        if (unlikely(rt_prio(p->prio))) {
+        if (unlikely(rt_prio(p->prio)) || p->policy == SCHED_LITMUS) {
                 resched_task(curr);
                 return;
         }
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index a4d790cddb19..f622880e918f 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1004,7 +1004,7 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
  */
 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
 {
-        if (p->prio < rq->curr->prio) {
+        if (p->prio < rq->curr->prio || p->policy == SCHED_LITMUS) {
                 resched_task(rq->curr);
                 return;
         }