Re: KVM host kernel hang

Alexander Graf
2009-01-07T19:08:49Z

On 07.01.2009, at 14:53, Avi Kivity <avi@redhat.com> wrote:

> Alexander Graf wrote:
>> Avi Kivity wrote:
>>
>>> Alexander Graf wrote:
>>>
>>>> I have CONFIG_LOCKDEP_SUPPORT=y. How do I make it detect that it's
>>>> actually locking itself up?
>>>> Btw: The issue seems to be easily reproducible :-)
>>>>
>>> Perhaps CONFIG_PROVE_LOCKING and CONFIG_LOCKDEP. _SUPPORT just
>>> indicates the arch can do it if you want, IIUC.
>>>
>>
>> I just added some debug #define's to show me where exactly things
>> break.
>>
>>
>> Jan 7 14:34:46 linux-dp8n kernel: 2149: Grabbing lock {
>> Jan 7 14:34:46 linux-dp8n kernel: 1908: Grabbing lock {
>>
>> 2145 mmio:
>> 2146 /*
>> 2147 * Is this MMIO handled locally?
>> 2148 */
>> 2149 mutex_lock(&vcpu->kvm->lock);
>> 2150 mmio_dev = vcpu_find_mmio_dev(vcpu, gpa, bytes, 0);
>> 2151 if (mmio_dev) {
>> 2152 kvm_iodevice_read(mmio_dev, gpa, bytes, val);
>> 2153 mutex_unlock(&vcpu->kvm->lock);
>> 2154 return X86EMUL_CONTINUE;
>> 2155 }
>> 2156 mutex_unlock(&vcpu->kvm->lock);
>>
>>
>
> The lock was lost here. But how?
>
>> 1901 case KVM_IRQ_LINE: {
>> 1902 struct kvm_irq_level irq_event;
>> 1903
>> 1904 r = -EFAULT;
>> 1905 if (copy_from_user(&irq_event, argp, sizeof
>> irq_event))
>> 1906 goto out;
>> 1907 if (irqchip_in_kernel(kvm)) {
>> 1908 mutex_lock(&kvm->lock);
>> 1909 kvm_set_irq(kvm,
>> KVM_USERSPACE_IRQ_SOURCE_ID,
>> 1910 irq_event.irq,
>> irq_event.level);
>> 1911 mutex_unlock(&kvm->lock);
>> 1912 r = 0;
>> 1913 }
>> 1914 break;
>> 1915 }
>>
>>
> This is your hung iothread trying to inject an interrupt. It's
> waiting for the lost lock.
>
> I suggest enabling all the lock debug magic you can find in kconfig.

I did that and still don't get anything. I'll try digging deeper into
this tomorrow.

Alex

>
>
> --
> error compiling committee.c: too many arguments to function
>