sched: Fix updating rq->max_idle_balance_cost and rq->next_balance in idle_balance() (0e5b5337) · Commits · 戴 / test

The following commit: ("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>

kernel/sched/fair.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -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 &&

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