From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH] kvm: improve comment on rcu use in irqfd_deassign Date: Sun, 6 Mar 2011 13:03:26 +0200 Message-ID: <20110306110326.GA23818@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33762 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752290Ab1CFLDg (ORCPT ); Sun, 6 Mar 2011 06:03:36 -0500 Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: The RCU use in kvm_irqfd_deassign is tricky: we have rcu_assign_pointer but no synchronize_rcu: synchronize_rcu is done by kvm_irq_routing_update which we share a spinlock with. Fix up a comment in an attempt to make this clearer. Signed-off-by: Michael S. Tsirkin --- virt/kvm/eventfd.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 2ca4535..3656849 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -313,8 +313,9 @@ kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi) if (irqfd->eventfd == eventfd && irqfd->gsi == gsi) { /* * This rcu_assign_pointer is needed for when - * another thread calls kvm_irqfd_update before - * we flush workqueue below. + * another thread calls kvm_irq_routing_update before + * we flush workqueue below (we synchronize with + * kvm_irq_routing_update using irqfds.lock). * It is paired with synchronize_rcu done by caller * of that function. */ -- 1.7.3.2.91.g446ac