[Minios-devel] [UNIKRAFT PATCH 20/23] lib/ukschedpreempt: Schedule threads

[Costin Lupu <costin.lupu@xxxxxxxxx>]

This patch adds the scheduling core function. We also add yield as it is, more
or less, a wrapper over the scheduling function.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
---
 lib/ukschedpreempt/schedpreempt.c | 58 ++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/lib/ukschedpreempt/schedpreempt.c 
b/lib/ukschedpreempt/schedpreempt.c
index c6963b2f..0a01c3df 100644
--- a/lib/ukschedpreempt/schedpreempt.c
+++ b/lib/ukschedpreempt/schedpreempt.c
@@ -33,6 +33,7 @@
  */
 
 #include <uk/plat/lcpu.h>
+#include <uk/plat/memory.h>
 #include <uk/plat/time.h>
 #include <uk/schedpreempt.h>
 #include <uk/prioq.h>
@@ -44,6 +45,45 @@ struct schedpreempt_private {
        struct uk_thread_list sleeping_threads;
 };
 
+static void schedpreempt_schedule(struct uk_sched *s,
+               struct uk_thread *current)
+{
+       struct schedpreempt_private *prv;
+       struct preempt_thread_attr *attr;
+       struct uk_thread *next;
+       int current_runnable;
+       prio_t highest_prio;
+
+       UK_ASSERT(s != NULL);
+       UK_ASSERT(current != NULL);
+
+       prv = s->prv;
+       attr = current->sched_prv;
+
+       highest_prio = prioq_highest_prio(&prv->ready_queue);
+
+       current_runnable = is_runnable(current);
+       if (current_runnable && attr->prio > highest_prio) {
+               /* There is no thread with higher priority, keep running ... */
+               return;
+       }
+
+       /* Pick up the next thread */
+       if (highest_prio >= UK_THREAD_ATTR_PRIO_MIN)
+               next = prioq_pop_for_prio(&prv->ready_queue, highest_prio);
+       else
+               next = uk_sched_get_idle(s);
+
+       /* Put current thread in the ready queue if runnable */
+       if (current_runnable && current != uk_sched_get_idle(s))
+               prioq_enqueue(&prv->ready_queue, current);
+
+       /* Notify the platform about the new thread */
+       ukplat_stack_set_current_thread(next);
+
+       /* Make the switch */
+       uk_sched_thread_switch(s, current, next);
+}
 
 static
 struct preempt_thread_attr *preempt_thread_attr_create(struct uk_alloc *a,
@@ -119,6 +159,13 @@ void schedpreempt_thread_remove(struct uk_sched *s, struct 
uk_thread *t)
        uk_thread_exit(t);
        UK_TAILQ_INSERT_HEAD(&s->exited_threads, t, thread_list);
 
+       if (t == uk_thread_current()) {
+               /* thread exiting */
+               schedpreempt_schedule(s, t);
+               UK_CRASH("schedule() returned!\n");
+       }
+       /* else thread killed */
+
        ukplat_lcpu_restore_irqf(flags);
 }
 
@@ -204,6 +251,15 @@ int schedpreempt_thread_get_tslice(struct uk_sched *s 
__unused,
        return 0;
 }
 
+static void schedpreempt_yield(struct uk_sched *s)
+{
+       unsigned long flags;
+
+       flags = ukplat_lcpu_save_irqf();
+       schedpreempt_schedule(s, uk_thread_current());
+       ukplat_lcpu_restore_irqf(flags);
+}
+
 struct uk_sched *uk_schedpreempt_init(struct uk_alloc *a)
 {
        struct uk_sched *sched = NULL;
@@ -222,7 +278,7 @@ struct uk_sched *uk_schedpreempt_init(struct uk_alloc *a)
        UK_TAILQ_INIT(&prv->sleeping_threads);
 
        uk_sched_init(sched,
-                       NULL,
+                       schedpreempt_yield,
                        schedpreempt_thread_add,
                        schedpreempt_thread_remove,
                        schedpreempt_thread_blocked,
-- 
2.20.1


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