Do processor state transitions in schedule_tail().

Fixes a bug in Litmus where processor scheduling states
could become corrupted. Corruption can occur when a
just-forked thread is externally forced to be scheduled
by SCHED_LITMUS before this just-forked thread can complete
post-fork processing. Specifically, before schedule_tail()
has completed.

1 files changed, 12 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 2229d0deec4b..65aba7ec564d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3163,16 +3163,26 @@ 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);
 
+        sched_trace_task_switch_to(current);
+
         /*
          * FIXME: do we need to worry about rq being invalidated by the
          * task_switch?
          */
         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();