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Commit b84ff7d6 authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

sched: Fix kthread_bind() by moving the body of kthread_bind() to sched.c 



Eric Paris reported that commit
f685ceac causes boot time
PREEMPT_DEBUG complaints.

 [    4.590699] BUG: using smp_processor_id() in preemptible [00000000] code: rmmod/1314
 [    4.593043] caller is task_hot+0x86/0xd0

Since kthread_bind() messes with scheduler internals, move the
body to sched.c, and lock the runqueue.

Reported-by: default avatarEric Paris <eparis@redhat.com>
Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Tested-by: default avatarEric Paris <eparis@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1256813310.7574.3.camel@marge.simson.net>
[ v2: fix !SMP build and clean up ]
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6b9de613

kernel/kthread.c

+0 −23
Original line number Diff line number Diff line
@@ -149,29 +149,6 @@ struct task_struct *kthread_create(int (*threadfn)(void *data), 
}

EXPORT_SYMBOL(kthread_create);



/**

 * kthread_bind - bind a just-created kthread to a cpu.

 * @k: thread created by kthread_create().

 * @cpu: cpu (might not be online, must be possible) for @k to run on.

 *

 * Description: This function is equivalent to set_cpus_allowed(),

 * except that @cpu doesn't need to be online, and the thread must be

 * stopped (i.e., just returned from kthread_create()).

 */

void kthread_bind(struct task_struct *k, unsigned int cpu)

{

	/* Must have done schedule() in kthread() before we set_task_cpu */

	if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {

		WARN_ON(1);

		return;

	}

	set_task_cpu(k, cpu);

	k->cpus_allowed = cpumask_of_cpu(cpu);

	k->rt.nr_cpus_allowed = 1;

	k->flags |= PF_THREAD_BOUND;

}

EXPORT_SYMBOL(kthread_bind);



/**

 * kthread_stop - stop a thread created by kthread_create().

 * @k: thread created by kthread_create().

kernel/sched.c

+32 −0
Original line number Diff line number Diff line
@@ -1996,6 +1996,38 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p, 
		p->sched_class->prio_changed(rq, p, oldprio, running);

}



/**

 * kthread_bind - bind a just-created kthread to a cpu.

 * @k: thread created by kthread_create().

 * @cpu: cpu (might not be online, must be possible) for @k to run on.

 *

 * Description: This function is equivalent to set_cpus_allowed(),

 * except that @cpu doesn't need to be online, and the thread must be

 * stopped (i.e., just returned from kthread_create()).

 *

 * Function lives here instead of kthread.c because it messes with

 * scheduler internals which require locking.

 */

void kthread_bind(struct task_struct *p, unsigned int cpu)

{

	struct rq *rq = cpu_rq(cpu);

	unsigned long flags;



	/* Must have done schedule() in kthread() before we set_task_cpu */

	if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {

		WARN_ON(1);

		return;

	}



	spin_lock_irqsave(&rq->lock, flags);

	set_task_cpu(p, cpu);

	p->cpus_allowed = cpumask_of_cpu(cpu);

	p->rt.nr_cpus_allowed = 1;

	p->flags |= PF_THREAD_BOUND;

	spin_unlock_irqrestore(&rq->lock, flags);

}

EXPORT_SYMBOL(kthread_bind);



#ifdef CONFIG_SMP

/*

 * Is this task likely cache-hot: