Re-implement non-preemptive section support.

Re-introduce NP sections in the configuration and in litmus.h. Remove the old
np_flag from rt_param.

If CONFIG_NP_SECTION is disabled, then all non-preemptive section checks are
constant expressions which should get removed by the dead code elimination
during optimization.

Instead of re-implementing sys_exit_np(), we simply repurposed sched_yield()
for calling into the scheduler to trigger delayed preemptions.

1 files changed, 7 insertions, 1 deletions

diff --git a/litmus/sched_litmus.c b/litmus/sched_litmus.c
index 64ad5db07795..c1fc7748e590 100644
--- a/litmus/sched_litmus.c
+++ b/litmus/sched_litmus.c
@@ -177,7 +177,13 @@ static void dequeue_task_litmus(struct rq *rq, struct task_struct *p, int sleep)
 static void yield_task_litmus(struct rq *rq)
 {
         BUG_ON(rq->curr != current);
-        litmus->complete_job();
+        /* sched_yield() is called to trigger delayed preemptions.
+         * Thus, mark the current task as needing to be rescheduled.
+         * This will cause the scheduler plugin to be invoked, which can
+         * then determine if a preemption is still required.
+         */
+        clear_exit_np(current);
+        set_tsk_need_resched(current);
 }
 
 /* Plugins are responsible for this.