Messages in this thread | | | Date | Fri, 30 Aug 2019 11:48:34 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v14 5/6] sched/core: uclamp: Update CPU's refcount on TG's clamp changes |
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On Thu, Aug 22, 2019 at 02:28:10PM +0100, Patrick Bellasi wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 04fc161e4dbe..fc2dc86a2abe 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1043,6 +1043,57 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) > uclamp_rq_dec_id(rq, p, clamp_id); > } > > +static inline void > +uclamp_update_active(struct task_struct *p, unsigned int clamp_id) > +{ > + struct rq_flags rf; > + struct rq *rq; > + > + /* > + * Lock the task and the rq where the task is (or was) queued. > + * > + * We might lock the (previous) rq of a !RUNNABLE task, but that's the > + * price to pay to safely serialize util_{min,max} updates with > + * enqueues, dequeues and migration operations. > + * This is the same locking schema used by __set_cpus_allowed_ptr(). > + */ > + rq = task_rq_lock(p, &rf);
Since modifying cgroup parameters is priv only, this should be OK I suppose. Priv can already DoS the system anyway.
> + /* > + * Setting the clamp bucket is serialized by task_rq_lock(). > + * If the task is not yet RUNNABLE and its task_struct is not > + * affecting a valid clamp bucket, the next time it's enqueued, > + * it will already see the updated clamp bucket value. > + */ > + if (!p->uclamp[clamp_id].active) > + goto done; > + > + uclamp_rq_dec_id(rq, p, clamp_id); > + uclamp_rq_inc_id(rq, p, clamp_id); > + > +done:
I'm thinking that:
if (p->uclamp[clamp_id].active) { uclamp_rq_dec_id(rq, p, clamp_id); uclamp_rq_inc_id(rq, p, clamp_id); }
was too obvious? ;-)
> + > + task_rq_unlock(rq, p, &rf); > +}
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