On Fri, Sep 14, 2018 at 10:07:51AM +0100, Patrick Bellasi wrote:

On 13-Sep 21:12, Peter Zijlstra wrote:

quoted

On Tue, Aug 28, 2018 at 02:53:11PM +0100, Patrick Bellasi wrote:

quoted

+static inline void uclamp_cpu_get_id(struct task_struct *p,
+				     struct rq *rq, int clamp_id)
+{
+	struct uclamp_group *uc_grp;
+	struct uclamp_cpu *uc_cpu;
+	int clamp_value;
+	int group_id;
+
+	/* Every task must reference a clamp group */
+	group_id = p->uclamp[clamp_id].group_id;

quoted

+}
+
+static inline void uclamp_cpu_put_id(struct task_struct *p,
+				     struct rq *rq, int clamp_id)
+{
+	struct uclamp_group *uc_grp;
+	struct uclamp_cpu *uc_cpu;
+	unsigned int clamp_value;
+	int group_id;
+
+	/* New tasks don't have a previous clamp group */
+	group_id = p->uclamp[clamp_id].group_id;
+	if (group_id == UCLAMP_NOT_VALID)
+		return;

*confused*, so on enqueue they must have a group_id, but then on dequeue
they might no longer have?

Why not ?

That's what it says on the tin, right? enqueue: "every task must reference clamp
group" while on dequeue: "new tasks don't have a (previous) clamp group"
and we check for NOT_VALID.