Litmus core: set state to TASK_RUNNING before calling wake_up()

Having tasks that are !is_running() in shared structures is
very confusing during development and debugging, and can likely
mask bugs and/or create races.

It seems like a strange choice that Linux changes a task's state
only _after_ activating it. For LITMUS^RT tasks, we change this order.

1 files changed, 10 insertions, 0 deletions

diff --git a/litmus/sched_litmus.c b/litmus/sched_litmus.c
index c65388969789..52afec278ec8 100644
--- a/litmus/sched_litmus.c
+++ b/litmus/sched_litmus.c
@@ -157,6 +157,16 @@ static void enqueue_task_litmus(struct rq *rq, struct task_struct *p,
         if (wakeup) {
                 sched_trace_task_resume(p);
                 tsk_rt(p)->present = 1;
+                /* LITMUS^RT plugins need to update the state
+                 * _before_ making it available in global structures.
+                 * Linux gets away with being lazy about the task state
+                 * update. We can't do that, hence we update the task
+                 * state already here.
+                 *
+                 * WARNING: this needs to be re-evaluated when porting
+                 *          to newer kernel versions.
+                 */
+                p->state = TASK_RUNNING;
                 litmus->task_wake_up(p);
 
                 rq->litmus.nr_running++;