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authorCornelia Huck <cornelia.huck@de.ibm.com>2014-03-17 19:11:35 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2014-03-18 17:06:04 +0100
commit684a0b719ddbbafe1c7e6646b9bc239453a1773d (patch)
treeeb83541090766873f36f9916e720ff0a85e1eeb2 /virt
parent93c4adc7afedf9b0ec190066d45b6d67db5270da (diff)
downloadkernel-684a0b719ddbbafe1c7e6646b9bc239453a1773d.tar.gz
KVM: eventfd: Fix lock order inversion.
When registering a new irqfd, we call its ->poll method to collect any event that might have previously been pending so that we can trigger it. This is done under the kvm->irqfds.lock, which means the eventfd's ctx lock is taken under it. However, if we get a POLLHUP in irqfd_wakeup, we will be called with the ctx lock held before getting the irqfds.lock to deactivate the irqfd, causing lockdep to complain. Calling the ->poll method does not really need the irqfds.lock, so let's just move it after we've given up the irqfds.lock in kvm_irqfd_assign(). Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/eventfd.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index abe4d6043b36..29c2a04e036e 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -391,19 +391,19 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
lockdep_is_held(&kvm->irqfds.lock));
irqfd_update(kvm, irqfd, irq_rt);
- events = f.file->f_op->poll(f.file, &irqfd->pt);
-
list_add_tail(&irqfd->list, &kvm->irqfds.items);
+ spin_unlock_irq(&kvm->irqfds.lock);
+
/*
* Check if there was an event already pending on the eventfd
* before we registered, and trigger it as if we didn't miss it.
*/
+ events = f.file->f_op->poll(f.file, &irqfd->pt);
+
if (events & POLLIN)
schedule_work(&irqfd->inject);
- spin_unlock_irq(&kvm->irqfds.lock);
-
/*
* do not drop the file until the irqfd is fully initialized, otherwise
* we might race against the POLLHUP