Integrate preemption state machine with Linux scheduler

Track when a processor is going to schedule "soon".

1 files changed, 20 insertions, 1 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5a51ce671fd2..b073ffda2bf2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1960,8 +1960,12 @@ static inline void post_schedule(struct rq *rq)
 asmlinkage void schedule_tail(struct task_struct *prev)
         __releases(rq->lock)
 {
-        struct rq *rq = this_rq();
+        struct rq *rq;
+
 
+        preempt_disable();
+
+        rq = this_rq();
         finish_task_switch(rq, prev);
 
         /*
@@ -1970,6 +1974,11 @@ asmlinkage void schedule_tail(struct task_struct *prev)
          */
         post_schedule(rq);
 
+        if (sched_state_validate_switch())
+                litmus_reschedule_local();
+
+        preempt_enable();
+
 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
         /* In this case, finish_task_switch does not reenable preemption */
         preempt_enable();
@@ -2967,11 +2976,16 @@ static 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);
         prev = rq->curr;
 
+        /* LITMUS^RT: quickly re-evaluate the scheduling decision
+         * if the previous one is no longer valid after context switch.
+         */
+litmus_need_resched_nonpreemptible:
         TS_SCHED_START;
 
         schedule_debug(prev);
@@ -3041,6 +3055,11 @@ need_resched:
 
         post_schedule(rq);
 
+        if (sched_state_validate_switch()) {
+                TS_SCHED2_END(prev);
+                goto litmus_need_resched_nonpreemptible;
+        }
+
         sched_preempt_enable_no_resched();
 
         TS_SCHED2_END(prev);