linux-kernel - set_task

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Date:	Wed, 2 Apr 2008 13:22:55 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	a.p.zijlstra@...llo.nl
Cc:	Ingo Molnar <mingo@...e.hu>, aneesh.kumar@...ux.vnet.ibm.com,
	dhaval@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Balbir Singh <balbir@...ibm.com>
Subject: set_task_rq bug?

For the case of CONFIG_RT_GROUP_SCHED and !CONFIG_FAIR_GROUP_SCHED, this
piece of code seems to be wrong?

/* Change a task's cfs_rq and parent entity if it moves across
 * CPUs/groups */
static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
{
#ifdef CONFIG_FAIR_GROUP_SCHED
        p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
        p->se.parent = task_group(p)->se[cpu];
#endif

#ifdef CONFIG_RT_GROUP_SCHED
        p->rt.rt_rq  = task_group(p)->rt_rq[cpu];
        p->rt.parent = task_group(p)->rt_se[cpu];
#endif
}

Basically for the above config case, a task's p->se.cfs_rq is never set,
which seems to be incorrect, as lot of sched_fair.c (for ex:
enqueue_task_fair) banks on the availability of this information. It should 
atleast be set to &rq->cfs?

-- 
Regards,
vatsa
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