On 18/12/2017 09:30, David Hildenbrand wrote: > The ugly thing in kvm_irqfd_assign() is that we access irqfd without > holding a lock. I think that should rather be fixed than working around > that issue. (e.g. lock() -> lookup again -> verify still in list -> > unlock()) I wonder if it's even simpler: diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index f2ac53ab8243..17ed298bd66f 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -387,7 +387,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) idx = srcu_read_lock(&kvm->irq_srcu); irqfd_update(kvm, irqfd); - srcu_read_unlock(&kvm->irq_srcu, idx); list_add_tail(&irqfd->list, &kvm->irqfds.items); @@ -420,10 +419,12 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) irqfd->consumer.token, ret); } #endif + srcu_read_unlock(&kvm->irq_srcu, idx); return 0; fail: + /* irq_srcu is *not* held here. */ if (irqfd->resampler) irqfd_resampler_shutdown(irqfd); Thanks, Paolo
