Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 054b9108 authored by Kirill Korotaev's avatar Kirill Korotaev Committed by Linus Torvalds
Browse files

[PATCH] move_task_off_dead_cpu() should be called with disabled ints 



move_task_off_dead_cpu() requires interrupts to be disabled, while
migrate_dead() calls it with enabled interrupts.  Added appropriate
comments to functions and added BUG_ON(!irqs_disabled()) into
double_rq_lock() and double_lock_balance() which are the origin sources of
such bugs.

Signed-off-by: default avatarKirill Korotaev <dev@openvz.org>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6711cab4

kernel/sched.c

+14 −3
Original line number Diff line number Diff line
@@ -1952,6 +1952,7 @@ static void double_rq_lock(struct rq *rq1, struct rq *rq2) 
	__acquires(rq1->lock)

	__acquires(rq2->lock)

{

	BUG_ON(!irqs_disabled());

	if (rq1 == rq2) {

		spin_lock(&rq1->lock);

		__acquire(rq2->lock);	/* Fake it out ;) */
@@ -1991,6 +1992,11 @@ static void double_lock_balance(struct rq *this_rq, struct rq *busiest) 
	__acquires(busiest->lock)

	__acquires(this_rq->lock)

{

	if (unlikely(!irqs_disabled())) {

		/* printk() doesn't work good under rq->lock */

		spin_unlock(&this_rq->lock);

		BUG_ON(1);

	}

	if (unlikely(!spin_trylock(&busiest->lock))) {

		if (busiest < this_rq) {

			spin_unlock(&this_rq->lock);
@@ -5067,7 +5073,10 @@ wait_to_die: 
}



#ifdef CONFIG_HOTPLUG_CPU

/* Figure out where task on dead CPU should go, use force if neccessary. */

/*

 * Figure out where task on dead CPU should go, use force if neccessary.

 * NOTE: interrupts should be disabled by the caller

 */

static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)

{

	unsigned long flags;
@@ -5187,6 +5196,7 @@ void idle_task_exit(void) 
	mmdrop(mm);

}



/* called under rq->lock with disabled interrupts */

static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)

{

	struct rq *rq = cpu_rq(dead_cpu);
@@ -5203,10 +5213,11 @@ static void migrate_dead(unsigned int dead_cpu, struct task_struct *p) 
	 * Drop lock around migration; if someone else moves it,

	 * that's OK.  No task can be added to this CPU, so iteration is

	 * fine.

	 * NOTE: interrupts should be left disabled  --dev@

	 */

	spin_unlock_irq(&rq->lock);

	spin_unlock(&rq->lock);

	move_task_off_dead_cpu(dead_cpu, p);

	spin_lock_irq(&rq->lock);

	spin_lock(&rq->lock);



	put_task_struct(p);

}