Re: [PATCH 4/4] Convert irq notifiers lists to RCU locking.

Gregory Haskins
2009-07-13T13:48:29Z

[-- Attachment #1: Type: text/plain, Size: 3499 bytes --]

Michael S. Tsirkin wrote:
> On Sun, Jul 12, 2009 at 03:03:53PM +0300, Gleb Natapov wrote:
>
>> Use RCU locking for mask/ack notifiers lists.
>>
>> Signed-off-by: Gleb Natapov <gleb@redhat.com>
>> ---
>> virt/kvm/irq_comm.c | 20 +++++++++++---------
>> 1 files changed, 11 insertions(+), 9 deletions(-)
>>
>> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
>> index 5dde1ef..ba3a115 100644
>> --- a/virt/kvm/irq_comm.c
>> +++ b/virt/kvm/irq_comm.c
>> @@ -179,18 +179,18 @@ void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
>> break;
>> }
>> }
>> - rcu_read_unlock();
>>
>> - hlist_for_each_entry(kian, n, &kvm->irq_ack_notifier_list, link)
>> + hlist_for_each_entry_rcu(kian, n, &kvm->irq_ack_notifier_list, link)
>> if (kian->gsi == gsi)
>> kian->irq_acked(kian);
>> + rcu_read_unlock();
>> }
>>
>> void kvm_register_irq_ack_notifier(struct kvm *kvm,
>> struct kvm_irq_ack_notifier *kian)
>> {
>> mutex_lock(&kvm->irq_lock);
>> - hlist_add_head(&kian->link, &kvm->irq_ack_notifier_list);
>> + hlist_add_head_rcu(&kian->link, &kvm->irq_ack_notifier_list);
>> mutex_unlock(&kvm->irq_lock);
>>
>
> I think we need synchronize_rcu here as well. If the user adds a
> notifier, he expects to get notified of irqs immediately
> after the function returns, not after the next rcu grace period.
>

Agreed.
>
>> }
>>
>> @@ -198,8 +198,9 @@ void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
>> struct kvm_irq_ack_notifier *kian)
>> {
>> mutex_lock(&kvm->irq_lock);
>> - hlist_del_init(&kian->link);
>> + hlist_del_init_rcu(&kian->link);
>> mutex_unlock(&kvm->irq_lock);
>> + synchronize_rcu();
>> }
>>
>> int kvm_request_irq_source_id(struct kvm *kvm)
>> @@ -246,7 +247,7 @@ void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq,
>> {
>> mutex_lock(&kvm->irq_lock);
>> kimn->irq = irq;
>> - hlist_add_head(&kimn->link, &kvm->mask_notifier_list);
>> + hlist_add_head_rcu(&kimn->link, &kvm->mask_notifier_list);
>> mutex_unlock(&kvm->irq_lock);
>> }
>>
>> @@ -254,8 +255,9 @@ void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
>> struct kvm_irq_mask_notifier *kimn)
>> {
>> mutex_lock(&kvm->irq_lock);
>> - hlist_del(&kimn->link);
>> + hlist_del_rcu(&kimn->link);
>> mutex_unlock(&kvm->irq_lock);
>> + synchronize_rcu();
>> }
>>
>> void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)
>> @@ -263,11 +265,11 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)
>> struct kvm_irq_mask_notifier *kimn;
>> struct hlist_node *n;
>>
>> - WARN_ON(!mutex_is_locked(&kvm->irq_lock));
>> -
>> - hlist_for_each_entry(kimn, n, &kvm->mask_notifier_list, link)
>> + rcu_read_lock();
>> + hlist_for_each_entry_rcu(kimn, n, &kvm->mask_notifier_list, link)
>> if (kimn->irq == irq)
>> kimn->func(kimn, mask);
>> + rcu_read_unlock();
>> }
>>
>> void kvm_free_irq_routing(struct kvm *kvm)
>> --
>> 1.6.2.1
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 266 bytes --]