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Commit f7b4cddc authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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do CPU_DEAD migrating under read_lock(tasklist) instead of write_lock_irq(tasklist) 

Currently move_task_off_dead_cpu() is called under
write_lock_irq(tasklist).  This means it can't use task_lock() which is
needed to improve migrating to take task's ->cpuset into account.

Change the code to call move_task_off_dead_cpu() with irqs enabled, and
change migrate_live_tasks() to use read_lock(tasklist).

This all is a preparation for the futher changes proposed by Cliff Wickman, see
	http://marc.info/?t=117327786100003



Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: Cliff Wickman <cpw@sgi.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cf7a4416

kernel/sched.c

+16 −6
Original line number Diff line number Diff line
@@ -5060,6 +5060,17 @@ static int migration_thread(void *data) 
}



#ifdef CONFIG_HOTPLUG_CPU



static int __migrate_task_irq(struct task_struct *p, int src_cpu, int dest_cpu)

{

	int ret;



	local_irq_disable();

	ret = __migrate_task(p, src_cpu, dest_cpu);

	local_irq_enable();

	return ret;

}



/*

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

 * NOTE: interrupts should be disabled by the caller
@@ -5098,7 +5109,7 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p) 
				       "longer affine to cpu%d\n",

				       p->pid, p->comm, dead_cpu);

		}

	} while (!__migrate_task(p, dead_cpu, dest_cpu));

	} while (!__migrate_task_irq(p, dead_cpu, dest_cpu));

}



/*
@@ -5126,7 +5137,7 @@ static void migrate_live_tasks(int src_cpu) 
{

	struct task_struct *p, *t;



	write_lock_irq(&tasklist_lock);

	read_lock(&tasklist_lock);



	do_each_thread(t, p) {

		if (p == current)
@@ -5136,7 +5147,7 @@ static void migrate_live_tasks(int src_cpu) 
			move_task_off_dead_cpu(src_cpu, p);

	} while_each_thread(t, p);



	write_unlock_irq(&tasklist_lock);

	read_unlock(&tasklist_lock);

}



/*
@@ -5214,11 +5225,10 @@ 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(&rq->lock);

	spin_unlock_irq(&rq->lock);

	move_task_off_dead_cpu(dead_cpu, p);

	spin_lock(&rq->lock);

	spin_lock_irq(&rq->lock);



	put_task_struct(p);

}