Re: [PATCH] kvm/ia64: Ensure SIGINT delivered to main thread (vcpu

[Avi Kivity <avi@redhat.com>]

Zhang, Xiantao wrote:
> Avi Kivity wrote:
>   
>> Zhang, Xiantao wrote:
>>     
>>> Before Aps going to block status, it should make sure SIGINT is
>>> masked, otherwise, it may eat SIGINT from user killing the guest, and
>>> results in Qemu hanging there, becasue main thread can't get it to
>>> free guest's resource. 
>>>
>>>       
>>>  	vcpu_load(vcpu);
>>>
>>> +	if (vcpu->sigset_active)
>>> +		sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); +
>>>  	if (unlikely(vcpu->arch.mp_state = KVM_MP_STATE_UNINITIALIZED))
>>>       
> {
>   
>>>  		kvm_vcpu_block(vcpu);
>>>  		clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
>>> @@ -680,9 +683,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu
>>>  		*vcpu, struct kvm_run *kvm_run) return -EAGAIN;
>>>
>>>       
>> The 'return' here means you are returning with the wrong signal mask.
>>     
>
> Yes, but the signal is eaten by the thread, and can't be delivered to
> main thread when returing to usespace. So in order to ensure the main
> thread receive the signal SIGINT we should mask this signal on Aps going
> into halt, and only main thread can receive such signals. 
>
>   

Then you should block SIGINT in the vcpu thread in userspace.

This patch is correct, except that it leaks the signal mask. You need to 
restore it when you return -EAGAIN.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.