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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160310120025.169219710@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
hifive-unleashed-5.1
Peter Zijlstra 2016-03-10 12:54:14 +01:00 committed by Thomas Gleixner
parent 40190a78f8
commit b2454caa89
2 changed files with 14 additions and 15 deletions
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15
kernel/cpu.c
View File

@ -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);

14
kernel/sched/core.c
View File

@ -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;