Re: [PATCH 18/15] kvm: Replace vcpu->swait with rcuwait

Davidlohr Bueso
2020-03-22T16:34:30Z

On Fri, 20 Mar 2020, Peter Zijlstra wrote:

>On Fri, Mar 20, 2020 at 01:55:26AM -0700, Davidlohr Bueso wrote:
>> - swait_event_interruptible_exclusive(*wq, ((!vcpu->arch.power_off) &&
>> - (!vcpu->arch.pause)));
>> + rcuwait_wait_event(*wait,
>> + (!vcpu->arch.power_off) && (!vcpu->arch.pause),
>> + TASK_INTERRUPTIBLE);
>
>> - for (;;) {
>> - prepare_to_swait_exclusive(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
>> -
>> - if (kvm_vcpu_check_block(vcpu) < 0)
>> - break;
>> -
>> - waited = true;
>> - schedule();
>> - }
>> -
>> - finish_swait(&vcpu->wq, &wait);
>> + rcuwait_wait_event(&vcpu->wait,
>> + (block_check = kvm_vcpu_check_block(vcpu)) < 0,
>> + TASK_INTERRUPTIBLE);
>
>Are these yet more instances that really want to be TASK_IDLE ?

Hmm probably as it makes sense for a blocked vcpu not to be contributing to
the loadavg. So if this is the only reason to use interruptible, then yes we
ought to change it.

However, I'll make this a separate patch, given this (ab)use isn't as obvious
as the PS3 case, which is a kthread and therefore signals are masked.

Thanks,
Davidlohr