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author | Cornelia Huck <cornelia.huck@de.ibm.com> | 2014-03-17 19:11:35 +0100 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-03-18 17:06:04 +0100 |
commit | 684a0b719ddbbafe1c7e6646b9bc239453a1773d (patch) | |
tree | eb83541090766873f36f9916e720ff0a85e1eeb2 | |
parent | 93c4adc7afedf9b0ec190066d45b6d67db5270da (diff) | |
download | linux-684a0b719ddbbafe1c7e6646b9bc239453a1773d.tar.gz linux-684a0b719ddbbafe1c7e6646b9bc239453a1773d.tar.bz2 linux-684a0b719ddbbafe1c7e6646b9bc239453a1773d.zip |
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>
-rw-r--r-- | virt/kvm/eventfd.c | 8 |
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 |