Merge pull request #140 from sched-ext/htejun

Fix invalid state transition while scheduler is loaded

kernel/sched/ext.c

@@ -2353,26 +2353,30 @@ static enum scx_task_state scx_get_task_state(const struct task_struct *p)
 static void scx_set_task_state(struct task_struct *p, enum scx_task_state state)
 {
 	enum scx_task_state prev_state = scx_get_task_state(p);
+	bool warn = false;
 
 	BUILD_BUG_ON(SCX_TASK_NR_STATES > (1 << SCX_TASK_STATE_BITS));
 
 	switch (state) {
 	case SCX_TASK_NONE:
 		break;
 	case SCX_TASK_INIT:
-		WARN_ON_ONCE(prev_state != SCX_TASK_NONE);
+		warn = prev_state != SCX_TASK_NONE;
 		break;
 	case SCX_TASK_READY:
-		WARN_ON_ONCE(prev_state == SCX_TASK_NONE);
+		warn = prev_state == SCX_TASK_NONE;
 		break;
 	case SCX_TASK_ENABLED:
-		WARN_ON_ONCE(prev_state != SCX_TASK_READY);
+		warn = prev_state != SCX_TASK_READY;
 		break;
 	default:
-		WARN_ON_ONCE(true);
+		warn = true;
 		return;
 	}
 
+	WARN_ONCE(warn, "sched_ext: Invalid task state transition %d -> %d for %s[%d]",
+		  prev_state, state, p->comm, p->pid);
+
 	p->scx.flags &= ~SCX_TASK_STATE_MASK;
 	p->scx.flags |= state << SCX_TASK_STATE_SHIFT;
 }
@@ -3347,21 +3351,16 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
 	while ((p = scx_task_iter_next_filtered_locked(&sti))) {
 		const struct sched_class *old_class = p->sched_class;
 		struct sched_enq_and_set_ctx ctx;
-		bool alive = READ_ONCE(p->__state) != TASK_DEAD;
 
 		sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
 
 		p->scx.slice = min_t(u64, p->scx.slice, SCX_SLICE_DFL);
-
 		__setscheduler_prio(p, p->prio);
-		if (alive)
-			check_class_changing(task_rq(p), p, old_class);
+		check_class_changing(task_rq(p), p, old_class);
 
 		sched_enq_and_set_task(&ctx);
 
-		if (alive)
-			check_class_changed(task_rq(p), p, old_class, p->prio);
-
+		check_class_changed(task_rq(p), p, old_class, p->prio);
 		scx_ops_exit_task(p);
 	}
 	scx_task_iter_exit(&sti);
@@ -3830,23 +3829,18 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 
 	scx_task_iter_init(&sti);
 	while ((p = scx_task_iter_next_filtered_locked(&sti))) {
-		if (READ_ONCE(p->__state) != TASK_DEAD) {
-			const struct sched_class *old_class = p->sched_class;
-			struct sched_enq_and_set_ctx ctx;
+		const struct sched_class *old_class = p->sched_class;
+		struct sched_enq_and_set_ctx ctx;
 
-			sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE,
-					       &ctx);
+		sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx);
 
-			scx_set_task_state(p, SCX_TASK_READY);
-			__setscheduler_prio(p, p->prio);
-			check_class_changing(task_rq(p), p, old_class);
+		scx_set_task_state(p, SCX_TASK_READY);
+		__setscheduler_prio(p, p->prio);
+		check_class_changing(task_rq(p), p, old_class);
 
-			sched_enq_and_set_task(&ctx);
+		sched_enq_and_set_task(&ctx);
 
-			check_class_changed(task_rq(p), p, old_class, p->prio);
-		} else {
-			scx_ops_exit_task(p);
-		}
+		check_class_changed(task_rq(p), p, old_class, p->prio);
 	}
 	scx_task_iter_exit(&sti);