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Commit 07f06cb3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: Start stopper early 



Ensure the stopper thread is active 'early', because the load balancer
pretty much assumes that its available. And when 'online && active' the
load-balancer is fully available.

Not only the numa balancing stop_two_cpus() caller relies on it, but
also the self migration stuff does, and at CPU_ONLINE time the cpu
really is 'free' to run anything.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151009160054.GA10176@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f0cf16cb

kernel/cpu.c

+0 −1
Original line number Diff line number Diff line
@@ -475,7 +475,6 @@ static int smpboot_thread_call(struct notifier_block *nfb, 


	case CPU_DOWN_FAILED:

	case CPU_ONLINE:

		stop_machine_unpark(cpu);

		smpboot_unpark_threads(cpu);

		break;

kernel/sched/core.c

+9 −3
Original line number Diff line number Diff line
@@ -5545,21 +5545,27 @@ static void set_cpu_rq_start_time(void) 
static int sched_cpu_active(struct notifier_block *nfb,

				      unsigned long action, void *hcpu)

{

	int cpu = (long)hcpu;



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_STARTING:

		set_cpu_rq_start_time();

		return NOTIFY_OK;



	case CPU_ONLINE:

		/*

		 * At this point a starting CPU has marked itself as online via

		 * set_cpu_online(). But it might not yet have marked itself

		 * as active, which is essential from here on.

		 *

		 * Thus, fall-through and help the starting CPU along.

		 */

		set_cpu_active(cpu, true);

		stop_machine_unpark(cpu);

		return NOTIFY_OK;



	case CPU_DOWN_FAILED:

		set_cpu_active((long)hcpu, true);

		set_cpu_active(cpu, true);

		return NOTIFY_OK;



	default:

		return NOTIFY_DONE;

	}