Re: [PATCH] rcu: shrink each possible cpu krcp

Uladzislau Rezki
2020-08-14T18:51:32Z

> From: Zqiang <qiang.zhang@windriver.com>
>
> Due to cpu hotplug. some cpu may be offline after call "kfree_call_rcu"
> func, if the shrinker is triggered at this time, we should drain each
> possible cpu "krcp".
>
> Signed-off-by: Zqiang <qiang.zhang@windriver.com>
> ---
> kernel/rcu/tree.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 8ce77d9ac716..619ccbb3fe4b 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3443,7 +3443,7 @@ kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
> unsigned long count = 0;
>
> /* Snapshot count of all CPUs */
> - for_each_online_cpu(cpu) {
> + for_each_possible_cpu(cpu) {
> struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
>
> count += READ_ONCE(krcp->count);
> @@ -3458,7 +3458,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> int cpu, freed = 0;
> unsigned long flags;
>
> - for_each_online_cpu(cpu) {
> + for_each_possible_cpu(cpu) {
> int count;
> struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
>
> @@ -3491,7 +3491,7 @@ void __init kfree_rcu_scheduler_running(void)
> int cpu;
> unsigned long flags;
>
> - for_each_online_cpu(cpu) {
> + for_each_possible_cpu(cpu) {
> struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
>
> raw_spin_lock_irqsave(&krcp->lock, flags);
>
I agree that it can happen.

Joel, what is your view?

Thanks!

--
Vlad Rezki