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sched: Fix load corruption from update_cfs_shares() 

As part of enqueue_entity both a new entity weight and its contribution to the
queuing cfs_rq / rq are updated.  Since update_cfs_shares will only update the
queueing weights when the entity is on_rq (which in this case it is not yet),
there's a dependency loop here:

update_cfs_shares needs account_entity_enqueue to update cfs_rq->load.weight
account_entity_enqueue needs the updated weight for the queuing cfs_rq load[*]

Fix this and avoid spurious dequeue/enqueues by issuing update_cfs_shares as
if we had accounted the enqueue already.

This was also resulting in rq->load corruption previously.

[*]: this dependency also exists when using the group cfs_rq w/
     update_cfs_shares as the weight of the enqueued entity changes
     without the load being updated.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101115234937.844900206@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul Turner 2010-11-15 15:47:03 -08:00 committed by Ingo Molnar
parent 9e3081ca61
commit f0d7442a59
1 changed files with 8 additions and 8 deletions
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16
kernel/sched_fair.c
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@ -718,7 +718,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
account_entity_enqueue(cfs_rq, se);
}
static void update_cfs_shares(struct cfs_rq *cfs_rq)
static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
{
struct task_group *tg;
struct sched_entity *se;
@ -732,7 +732,7 @@ static void update_cfs_shares(struct cfs_rq *cfs_rq)
if (!se)
return;
load = cfs_rq->load.weight;
load = cfs_rq->load.weight + weight_delta;
load_weight = atomic_read(&tg->load_weight);
load_weight -= cfs_rq->load_contribution;
@ -754,7 +754,7 @@ static inline void update_cfs_load(struct cfs_rq *cfs_rq, int lb)
{
}
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
static inline void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */
@ -881,8 +881,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
*/
update_curr(cfs_rq);
update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq, se->load.weight);
account_entity_enqueue(cfs_rq, se);
update_cfs_shares(cfs_rq);
if (flags & ENQUEUE_WAKEUP) {
place_entity(cfs_rq, se, 0);
@ -944,7 +944,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
update_cfs_load(cfs_rq, 0);
account_entity_dequeue(cfs_rq, se);
update_min_vruntime(cfs_rq);
update_cfs_shares(cfs_rq);
update_cfs_shares(cfs_rq, 0);
/*
* Normalize the entity after updating the min_vruntime because the
@ -1177,7 +1177,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
struct cfs_rq *cfs_rq = cfs_rq_of(se);
update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
update_cfs_shares(cfs_rq, 0);
}
hrtick_update(rq);
@ -1207,7 +1207,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
struct cfs_rq *cfs_rq = cfs_rq_of(se);
update_cfs_load(cfs_rq, 0);
update_cfs_shares(cfs_rq);
update_cfs_shares(cfs_rq, 0);
}
hrtick_update(rq);
@ -2034,7 +2034,7 @@ static int tg_shares_up(struct task_group *tg, int cpu)
* We need to update shares after updating tg->load_weight in
* order to adjust the weight of groups with long running tasks.
*/
update_cfs_shares(cfs_rq);
update_cfs_shares(cfs_rq, 0);
raw_spin_unlock_irqrestore(&rq->lock, flags);