LITMUS: avoid using the same stack on two CPUs in global schedulers

This change fixes a race where a job could be executed on more than one
CPU, which to random crashes.

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 441996e08c..d9e876fea8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1897,6 +1897,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
         finish_arch_switch(prev);
         litmus->finish_switch(prev);
         finish_lock_switch(rq, prev);
+        prev->rt_param.stack_in_use = NO_CPU;
         fire_sched_in_preempt_notifiers(current);
         if (mm)
                 mmdrop(mm);
@@ -3679,6 +3680,7 @@ need_resched_nonpreemptible:
                 rq->curr = next;
                 ++*switch_count;
 
+                TRACE_TASK(next, "switched to\n");
                 context_switch(rq, prev, next); /* unlocks the rq */
         } else
                 spin_unlock_irq(&rq->lock);
@@ -4391,8 +4393,10 @@ recheck:
         oldprio = p->prio;
         __setscheduler(rq, p, policy, param->sched_priority);
 
-        if (policy == SCHED_LITMUS)
+        if (policy == SCHED_LITMUS) {
+                p->rt_param.stack_in_use = running ? rq->cpu : NO_CPU;
                 litmus->task_new(p, on_rq, running);
+        }
 
         if (on_rq) {
                 if (running)