Fix kernel segfault on boot

 - Since the last version of LITMUS, the pick_next_task function for
   scheduler classes has changed a bit; now the "prev" argument can be
   NULL. This change fixes how LITMUS' scheduler class stubs handle
   this, but further attention may need to be given to fix the
   non-default LITMUS plugins.

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/sched/litmus.c b/kernel/sched/litmus.c
index aa43ed1e9eb5..468aa0197d1d 100644
--- a/kernel/sched/litmus.c
+++ b/kernel/sched/litmus.c
@@ -273,7 +273,7 @@ static struct task_struct *pick_next_task_litmus(struct rq *rq,
         if (rf) {
                 cookie = rf->cookie;
         }
-        if (is_realtime(prev))
+        if (prev && is_realtime(prev))
                 update_time_litmus(rq, prev);
 
         lockdep_unpin_lock(&rq->lock, cookie);
@@ -291,7 +291,7 @@ static struct task_struct *pick_next_task_litmus(struct rq *rq,
          * provide a task, and if we find one, call put_prev_task() on the
          * previously scheduled task.
          */
-        if (next)
+        if (next && prev)
                 put_prev_task(rq, prev);
 
         return next;