KVM: improve comment on rcu use in irqfd_deassign
authorMichael S. Tsirkin <mst@redhat.com>
Sun, 6 Mar 2011 11:03:26 +0000 (13:03 +0200)
committerMarcelo Tosatti <mtosatti@redhat.com>
Thu, 17 Mar 2011 16:08:33 +0000 (13:08 -0300)
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 <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
virt/kvm/eventfd.c

index 2ca4535f4fb76b2629986e29c6225e77febdd698..3656849f78a0b722236f25eefd58dac4fc839dcf 100644 (file)
@@ -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.
                         */