Commit 371cbb38 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

kthreads: simplify migration_thread() exit path 



Now that kthread_stop() can be used even if the task has already exited,
we can kill the "wait_to_die:" loop in migration_thread().  But we must
pin rq->migration_thread after creation.

Actually, I don't think CPU_UP_CANCELED or CPU_DEAD should wait for
->migration_thread exit.  Perhaps we can simplify this code a bit more.
migration_call() can set ->should_stop and forget about this thread.  But
we need a new helper in kthred.c for that.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Vitaliy Gusev <vgusev@openvz.org
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 63706172

kernel/sched.c

+4 −10
Original line number Diff line number Diff line
@@ -7045,7 +7045,7 @@ static int migration_thread(void *data) 


		if (cpu_is_offline(cpu)) {

			spin_unlock_irq(&rq->lock);

			goto wait_to_die;

			break;

		}



		if (rq->active_balance) {
@@ -7071,16 +7071,7 @@ static int migration_thread(void *data) 
		complete(&req->done);

	}

	__set_current_state(TASK_RUNNING);

	return 0;



wait_to_die:

	/* Wait for kthread_stop */

	set_current_state(TASK_INTERRUPTIBLE);

	while (!kthread_should_stop()) {

		schedule();

		set_current_state(TASK_INTERRUPTIBLE);

	}

	__set_current_state(TASK_RUNNING);

	return 0;

}
@@ -7494,6 +7485,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) 
		rq = task_rq_lock(p, &flags);

		__setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);

		task_rq_unlock(rq, &flags);

		get_task_struct(p);

		cpu_rq(cpu)->migration_thread = p;

		break;
@@ -7524,6 +7516,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) 
		kthread_bind(cpu_rq(cpu)->migration_thread,

			     cpumask_any(cpu_online_mask));

		kthread_stop(cpu_rq(cpu)->migration_thread);

		put_task_struct(cpu_rq(cpu)->migration_thread);

		cpu_rq(cpu)->migration_thread = NULL;

		break;
@@ -7533,6 +7526,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) 
		migrate_live_tasks(cpu);

		rq = cpu_rq(cpu);

		kthread_stop(rq->migration_thread);

		put_task_struct(rq->migration_thread);

		rq->migration_thread = NULL;

		/* Idle task back to normal (off runqueue, low prio) */

		spin_lock_irq(&rq->lock);

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