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Commit b2454caa authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

sched/hotplug: Move sync_rcu to be with set_cpu_active(false) 



The sync_rcu stuff is specificically for clearing bits in the active
mask, such that everybody will observe the bit cleared and will not
consider the cleared CPU for load-balancing etc.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160310120025.169219710@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 40190a78

kernel/cpu.c

+0 −15
Original line number Diff line number Diff line
@@ -703,21 +703,6 @@ static int takedown_cpu(unsigned int cpu) 
	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);

	int err;



	/*

	 * By now we've cleared cpu_active_mask, wait for all preempt-disabled

	 * and RCU users of this state to go away such that all new such users

	 * will observe it.

	 *

	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might

	 * not imply sync_sched(), so wait for both.

	 *

	 * Do sync before park smpboot threads to take care the rcu boost case.

	 */

	if (IS_ENABLED(CONFIG_PREEMPT))

		synchronize_rcu_mult(call_rcu, call_rcu_sched);

	else

		synchronize_rcu();



	/* Park the smpboot threads */

	kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);

	smpboot_park_threads(cpu);

kernel/sched/core.c

+14 −0
Original line number Diff line number Diff line
@@ -7112,6 +7112,20 @@ int sched_cpu_deactivate(unsigned int cpu) 
	int ret;



	set_cpu_active(cpu, false);

	/*

	 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU

	 * users of this state to go away such that all new such users will

	 * observe it.

	 *

	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might

	 * not imply sync_sched(), so wait for both.

	 *

	 * Do sync before park smpboot threads to take care the rcu boost case.

	 */

	if (IS_ENABLED(CONFIG_PREEMPT))

		synchronize_rcu_mult(call_rcu, call_rcu_sched);

	else

		synchronize_rcu();



	if (!sched_smp_initialized)

		return 0;