linux-kernel - [Query]: sched/fair: prio_changed

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Message-ID: <CAKohpomr6wkNNi3tt=obzM=2atZfRLQ0V4XOzX__W1yB8UKgTg@mail.gmail.com>
Date:	Wed, 7 Nov 2012 13:19:01 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	mingo@...hat.com, Peter Zijlstra <peterz@...radead.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lists linaro-dev <linaro-dev@...ts.linaro.org>,
	PDSW-power-team <pdsw-power-team@....com>
Subject: [Query]: sched/fair: prio_changed_fair()

Hi Ingo/Peter,

I am trying to understand the complex scheduler code and just found
something incorrect (maybe i am not reading it well):

File: kernel/sched/fair.c

static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
{
	if (!p->se.on_rq)
		return;

	/*
	 * Reschedule if we are currently running on this runqueue and
	 * our priority decreased, or if we are not currently running on
	 * this runqueue and our priority is higher than the current's
	 */
	if (rq->curr == p) {
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
		check_preempt_curr(rq, p, 0);
}


Comment says that we must mark the task to be rescheduled, if we
are currently running and our priority has decreased. But in code we
are checking (p->prio > oldprio). i.e. reschedule if we were currently
running and our priority increased.

Sorry if i am wrong :(

--
viresh
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