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sched: Fix updating rq->max_idle_balance_cost and rq->next_balance in idle_balance()

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The following commit:

  e5fc66119e ("sched: Fix race in idle_balance()")

can potentially cause rq->max_idle_balance_cost to not be updated,
even when load_balance(NEWLY_IDLE) is attempted and the per-sd
max cost value is updated.

Preeti noticed a similar issue with updating rq->next_balance.

In this patch, we fix this by making sure we still check/update those values
even if a task gets enqueued while browsing the domains.

Signed-off-by: Jason Low <jason.low2@hp.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: morten.rasmussen@arm.com
Cc: aswin@hp.com
Cc: daniel.lezcano@linaro.org
Cc: alex.shi@linaro.org
Cc: efault@gmx.de
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1398725155-7591-2-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Jason Low 2014-04-28 15:45:54 -07:00 committed by Ingo Molnar
parent 6ccdc84b81
commit 0e5b5337f0
1 changed files with 8 additions and 8 deletions
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16
kernel/sched/fair.c
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@ -6653,6 +6653,7 @@ static int idle_balance(struct rq *this_rq)
int this_cpu = this_rq->cpu;
idle_enter_fair(this_rq);
/*
* We must set idle_stamp _before_ calling idle_balance(), such that we
* measure the duration of idle_balance() as idle time.
@ -6705,14 +6706,16 @@ static int idle_balance(struct rq *this_rq)
raw_spin_lock(&this_rq->lock);
if (curr_cost > this_rq->max_idle_balance_cost)
this_rq->max_idle_balance_cost = curr_cost;
/*
* While browsing the domains, we released the rq lock.
* A task could have be enqueued in the meantime
* While browsing the domains, we released the rq lock, a task could
* have been enqueued in the meantime. Since we're not going idle,
* pretend we pulled a task.
*/
if (this_rq->cfs.h_nr_running && !pulled_task) {
if (this_rq->cfs.h_nr_running && !pulled_task)
pulled_task = 1;
goto out;
}
if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
/*
@ -6722,9 +6725,6 @@ static int idle_balance(struct rq *this_rq)
this_rq->next_balance = next_balance;
}
if (curr_cost > this_rq->max_idle_balance_cost)
this_rq->max_idle_balance_cost = curr_cost;
out:
/* Is there a task of a high priority class? */
if (this_rq->nr_running != this_rq->cfs.h_nr_running &&