On 08/06/2018 06:39 PM, Patrick Bellasi wrote:
[...]
+/**
+ * uclamp_cpu_put_id(): decrease reference count for a clamp group on a CPU
+ * @p: the task being dequeued from a CPU
+ * @cpu: the CPU from where the clamp group has to be released
+ * @clamp_id: the utilization clamp (e.g. min or max utilization) to release
+ *
+ * When a task is dequeued from a CPU's RQ, the CPU's clamp group reference
+ * counted by the task is decreased.
+ * If this was the last task defining the current max clamp group, then the
+ * CPU clamping is updated to find the new max for the specified clamp
+ * index.
+ */
+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;
+
+ /* No task specific clamp values: nothing to do */
+ group_id = p->uclamp[clamp_id].group_id;
+ if (group_id == UCLAMP_NOT_VALID)
+ return;
+
+ /* Decrement the task's reference counted group index */
+ uc_grp = &rq->uclamp.group[clamp_id][0];
+#ifdef SCHED_DEBUG
+ if (unlikely(uc_grp[group_id].tasks == 0)) {
+ WARN(1, "invalid CPU[%d] clamp group [%d:%d] refcount\n",
+ cpu_of(rq), clamp_id, group_id);
+ uc_grp[group_id].tasks = 1;
+ }
+#endif
This one indicates that there are some holes in your ref-counting. It's
probably easier to debug that there is still a task but the
uc_grp[group_id].tasks value == 0 (A). I assume the other problem exists
as well, i.e. last task and uc_grp[group_id].tasks > 1 (B)?
You have uclamp_cpu_[get/put](_id)() in [enqueue/dequeue]_task.
Patch 04/14 introduces its use in uclamp_task_update_active().
Do you know why (A) (and (B)) are happening?
+ uc_grp[group_id].tasks -= 1;
+
+ /* If this is not the last task, no updates are required */
+ if (uc_grp[group_id].tasks > 0)
+ return;
+
+ /*
+ * Update the CPU only if this was the last task of the group
+ * defining the current clamp value.
+ */
+ uc_cpu = &rq->uclamp;
+ clamp_value = uc_grp[group_id].value;
+ if (clamp_value >= uc_cpu->value[clamp_id])
'clamp_value > uc_cpu->value[clamp_id]' should indicate another
inconsistency in the uclamp machinery, right?
[...]
