1 files changed, 11 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 6777dc7942a0..1b13c8e1cfc2 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -82,6 +82,8 @@
 #include <litmus/sched_trace.h>
 #include <litmus/trace.h>
 
+static void litmus_tick(struct rq*, struct task_struct*);
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/sched.h>
 
@@ -576,8 +578,14 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
          * A queue event has occurred, and we're going to schedule.  In
          * this case, we can save a useless back to back clock update.
          */
+        /* LITMUS^RT: turning off the clock update is buggy in Linux 2.6.36;
+         * the scheduler can "forget" to renable the runqueue clock in some
+         * cases. LITMUS^RT amplifies the effects of this problem. Hence, we
+         * turn it off to avoid stalling clocks. */
+        /*
         if (test_tsk_need_resched(p))
                 rq->skip_clock_update = 1;
+        */
 }
 
 static inline int cpu_of(struct rq *rq)
@@ -1052,6 +1060,7 @@ static enum hrtimer_restart hrtick(struct hrtimer *timer)
         raw_spin_lock(&rq->lock);
         update_rq_clock(rq);
         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
+        litmus_tick(rq, rq->curr);
         raw_spin_unlock(&rq->lock);
 
         return HRTIMER_NORESTART;
@@ -3791,6 +3800,7 @@ asmlinkage void __sched schedule(void)
 
 need_resched:
         preempt_disable();
+        sched_state_entered_schedule();
         cpu = smp_processor_id();
         rq = cpu_rq(cpu);
         rcu_note_context_switch(cpu);
@@ -3869,7 +3879,7 @@ need_resched_nonpreemptible:
 
         post_schedule(rq);
 
-        if (unlikely(reacquire_kernel_lock(prev)))
+        if (sched_state_validate_switch() || unlikely(reacquire_kernel_lock(prev)))
                 goto need_resched_nonpreemptible;
 
         preempt_enable_no_resched();