Merge pull request torvalds#111 from sched-ext/htejun

include/linux/sched/ext.h

@@ -613,15 +613,24 @@ enum scx_ent_flags {
 	SCX_TASK_QUEUED		= 1 << 0, /* on ext runqueue */
 	SCX_TASK_BAL_KEEP	= 1 << 1, /* balance decided to keep current */
 	SCX_TASK_DDSP_PRIQ	= 1 << 2, /* task should be enqueued on priq when directly dispatched */
-	SCX_TASK_STATE_0	= 1 << 3, /* first bit encoding the task's current state */
-	SCX_TASK_STATE_1	= 1 << 4, /* second bit encoding the task's current state */
+	SCX_TASK_RESET_RUNNABLE_AT = 1 << 3, /* runnable_at should be reset */
+	SCX_TASK_DEQD_FOR_SLEEP	= 1 << 4, /* last dequeue was for SLEEP */
 
-	SCX_TASK_RESET_RUNNABLE_AT = 1 << 16, /* runnable_at should be reset */
-	SCX_TASK_DEQD_FOR_SLEEP	= 1 << 17, /* last dequeue was for SLEEP */
+	SCX_TASK_STATE_SHIFT	= 8,	  /* bit 8 and 9 are used to carry scx_task_state */
+	SCX_TASK_STATE_BITS	= 2,
+	SCX_TASK_STATE_MASK	= ((1 << SCX_TASK_STATE_BITS) - 1) << SCX_TASK_STATE_SHIFT,
 
 	SCX_TASK_CURSOR		= 1 << 31, /* iteration cursor, not a task */
+};
+
+/* scx_entity.flags & SCX_TASK_STATE_MASK */
+enum scx_task_state {
+	SCX_TASK_NONE,		/* ops.init_task() not called yet */
+	SCX_TASK_INIT,		/* ops.init_task() succeeded, but task can be cancelled */
+	SCX_TASK_READY,		/* fully initialized, but not in sched_ext */
+	SCX_TASK_ENABLED,	/* fully initialized and in sched_ext */
 
-	SCX_TASK_STATE_MASK	= SCX_TASK_STATE_0 | SCX_TASK_STATE_1,
+	SCX_TASK_NR_STATES,
 };
 
 /* scx_entity.dsq_flags */
@@ -655,21 +664,6 @@ enum scx_kf_mask {
 	__SCX_KF_TERMINAL	= SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU | SCX_KF_REST,
 };
 
-/* scx_entity.task_state */
-enum scx_task_state {
-	/* ops.prep_enable() has not yet been called on task */
-	SCX_TASK_NONE,
-
-	/* ops.prep_enable() succeeded on task, but it still be cancelled */
-	SCX_TASK_INIT,
-
-	/* Task is fully initialized, but not being scheduled in sched_ext */
-	SCX_TASK_READY,
-
-	/* Task is fully initialized and is being scheduled in sched_ext */
-	SCX_TASK_ENABLED,
-};
-
 /*
  * The following is embedded in task_struct and contains all fields necessary
  * for a task to be scheduled by SCX.

kernel/sched/ext.c

@@ -2313,41 +2313,34 @@ static struct cgroup *tg_cgrp(struct task_group *tg)
 
 static enum scx_task_state scx_get_task_state(const struct task_struct *p)
 {
-	int state = p->scx.flags & SCX_TASK_STATE_MASK;
-
-	switch (state) {
-	case SCX_TASK_STATE_0 | SCX_TASK_STATE_1:
-		return SCX_TASK_ENABLED;
-	case SCX_TASK_STATE_1:
-		return SCX_TASK_READY;
-	case SCX_TASK_STATE_0:
-		return SCX_TASK_INIT;
-	default:
-		return SCX_TASK_NONE;
-	}
+	return (p->scx.flags & SCX_TASK_STATE_MASK) >> SCX_TASK_STATE_SHIFT;
 }
 
 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);
 
-	p->scx.flags &= ~SCX_TASK_STATE_MASK;
+	BUILD_BUG_ON(SCX_TASK_NR_STATES > (1 << SCX_TASK_STATE_BITS));
+
 	switch (state) {
 	case SCX_TASK_NONE:
-		return;
+		break;
 	case SCX_TASK_INIT:
 		WARN_ON_ONCE(prev_state != SCX_TASK_NONE);
-		p->scx.flags |= SCX_TASK_STATE_0;
-		return;
+		break;
 	case SCX_TASK_READY:
 		WARN_ON_ONCE(prev_state == SCX_TASK_NONE);
-		p->scx.flags |= SCX_TASK_STATE_1;
-		return;
+		break;
 	case SCX_TASK_ENABLED:
 		WARN_ON_ONCE(prev_state != SCX_TASK_READY);
-		p->scx.flags |= (SCX_TASK_STATE_0 | SCX_TASK_STATE_1);
+		break;
+	default:
+		WARN_ON_ONCE(true);
 		return;
 	}
+
+	p->scx.flags &= ~SCX_TASK_STATE_MASK;
+	p->scx.flags |= state << SCX_TASK_STATE_SHIFT;
 }
 
 static int scx_ops_init_task(struct task_struct *p, struct task_group *tg)
@@ -2447,6 +2440,9 @@ static void scx_ops_exit_task(struct task_struct *p)
 	case SCX_TASK_ENABLED:
 		scx_ops_disable_task(p);
 		break;
+	default:
+		WARN_ON_ONCE(true);
+		return;
 	}
 
 	if (SCX_HAS_OP(exit_task))