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Commit c8ce057e authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Marcelo Tosatti
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KVM: improve comment on rcu use in irqfd_deassign 



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: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 676646ee

virt/kvm/eventfd.c

+3 −2
Original line number Original line Diff line number Diff line
@@ -313,8 +313,9 @@ kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi) 
		if (irqfd->eventfd == eventfd && irqfd->gsi == gsi) {

		if (irqfd->eventfd == eventfd && irqfd->gsi == gsi) {

			/*

			/*

			 * This rcu_assign_pointer is needed for when

			 * This rcu_assign_pointer is needed for when

			 * another thread calls kvm_irqfd_update before

			 * another thread calls kvm_irq_routing_update before

			 * we flush workqueue below.

			 * we flush workqueue below (we synchronize with

			 * kvm_irq_routing_update using irqfds.lock).

			 * It is paired with synchronize_rcu done by caller

			 * It is paired with synchronize_rcu done by caller

			 * of that function.

			 * of that function.

			 */

			 */