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KVM: Fix possible circular locking in kvm_vm_ioctl_assign_device()

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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.

Cc: stable@kernel.org
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Sheng Yang 2009-12-15 10:28:07 +08:00 committed by Marcelo Tosatti
parent fb341f572d
commit fae3a3536a
2 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
virt/kvm/assigned-dev.c
View File

@ -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 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
pci_dev_put(dev);
out_free:
kfree(match);
mutex_unlock(&kvm->lock);
up_read(&kvm->slots_lock);
mutex_unlock(&kvm->lock);
return r;
}

2
virt/kvm/kvm_main.c
View File

@ -64,7 +64,7 @@ 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);