From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sheng Yang Subject: [PATCH] KVM: Fix possible circular locking in kvm_vm_ioctl_assign_device() Date: Tue, 15 Dec 2009 10:28:07 +0800 Message-ID: <1260844087-5485-1-git-send-email-sheng@linux.intel.com> References: <20091214191233.GA6065@amt.cnet> Cc: Avi Kivity , kvm@vger.kernel.org, Sheng Yang To: Marcelo Tosatti Return-path: Received: from mga09.intel.com ([134.134.136.24]:59835 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758619AbZLOC2S (ORCPT ); Mon, 14 Dec 2009 21:28:18 -0500 In-Reply-To: <20091214191233.GA6065@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: One possible order is: KVM_CREATE_IRQCHIP ioctl(took kvm->lock) -> kvm_iobus_register_dev() -> down_write(kvm->slots_lock). The other one is in kvm_vm_ioctl_assign_device(), which take kvm->slots_lock first, then kvm->lock. Update the comment of lock order as well. Observe it due to kernel locking debug warnings. Signed-off-by: Sheng Yang --- virt/kvm/assigned-dev.c | 6 +++--- virt/kvm/kvm_main.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c index fd9c097..f73de63 100644 --- a/virt/kvm/assigned-dev.c +++ b/virt/kvm/assigned-dev.c @@ -508,8 +508,8 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm, struct kvm_assigned_dev_kernel *match; struct pci_dev *dev; - down_read(&kvm->slots_lock); mutex_lock(&kvm->lock); + down_read(&kvm->slots_lock); match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head, assigned_dev->assigned_dev_id); @@ -573,8 +573,8 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm, } out: - mutex_unlock(&kvm->lock); up_read(&kvm->slots_lock); + mutex_unlock(&kvm->lock); return r; out_list_del: list_del(&match->list); @@ -585,8 +585,8 @@ out_put: pci_dev_put(dev); out_free: kfree(match); - mutex_unlock(&kvm->lock); up_read(&kvm->slots_lock); + mutex_unlock(&kvm->lock); return r; } diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index f92ba13..91b84c9 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -63,7 +63,7 @@ MODULE_LICENSE("GPL"); /* * Ordering of locks: * - * kvm->slots_lock --> kvm->lock --> kvm->irq_lock + * kvm->lock --> kvm->slots_lock --> kvm->irq_lock */ DEFINE_SPINLOCK(kvm_lock); -- 1.5.4.5