On Tue, 2009-05-12 at 19:09 -0300, Marcelo Tosatti wrote: > KVM: workaround workqueue / deassign_host_irq deadlock > > I think I'm running into the following deadlock in the kvm kernel module > when trying to use device assignment: > > CPU A CPU B > kvm_vm_ioctl_deassign_dev_irq() > mutex_lock(&kvm->lock); worker_thread() > -> kvm_deassign_irq() -> > kvm_assigned_dev_interrupt_work_handler() > -> deassign_host_irq() mutex_lock(&kvm->lock); > -> cancel_work_sync() [blocked] > > Workaround the issue by dropping kvm->lock for cancel_work_sync(). > > Reported-by: Alex Williamson <[email protected]> > From: Sheng Yang <[email protected]> > Signed-off-by: Marcelo Tosatti <[email protected]>
Perfect, thanks. Acked-by: Alex Williamson <[email protected]> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 4d00942..d4af719 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -250,7 +250,15 @@ static void deassign_host_irq(struct kvm *kvm, > disable_irq_nosync(assigned_dev-> > host_msix_entries[i].vector); > > + /* > + * FIXME: kvm_assigned_dev_interrupt_work_handler can deadlock > + * with cancel_work_sync, since it requires kvm->lock for irq > + * injection. This is a hack, the irq code must use > + * a separate lock. Same below for MSI. > + */ > + mutex_unlock(&kvm->lock); > cancel_work_sync(&assigned_dev->interrupt_work); > + mutex_lock(&kvm->lock); > > for (i = 0; i < assigned_dev->entries_nr; i++) > free_irq(assigned_dev->host_msix_entries[i].vector, > @@ -263,7 +271,9 @@ static void deassign_host_irq(struct kvm *kvm, > } else { > /* Deal with MSI and INTx */ > disable_irq_nosync(assigned_dev->host_irq); > + mutex_unlock(&kvm->lock); > cancel_work_sync(&assigned_dev->interrupt_work); > + mutex_lock(&kvm->lock); > > free_irq(assigned_dev->host_irq, (void *)assigned_dev); > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
