Messages in this thread | | | Subject | Re: [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting | From | Dietmar Eggemann <> | Date | Tue, 14 Aug 2018 17:44:15 +0200 |
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On 08/06/2018 06:39 PM, Patrick Bellasi wrote:
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> +/** > + * 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?
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