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SubjectRe: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host
On Wed, 14 Dec 2011, Avi Kivity wrote:

> On 12/08/2011 05:19 PM, Eric B Munson wrote:
> > > error compiling committee.c: too many arguments to function
> > >
> > My concern for preempt notifiers is masking real soft lockup warnings. If the
> > flag is set every time the vm is preempted, it becomes more likely that we will
> > mask real warnings. The ioctl was choosen because it sets the flag only when
> > the guest is being paused deliberately.
> >
> > AFAIK, SIGSTOP is not a supported way to stop a qemu vm so a soft lockup
>
> This is a kvm patch, not a qemu patch. In general we try to address
> general requirements, not just those that are specific to one userspace,
> even if it is near to our hearts.
>
> > warning would be working as designed there. If that isn't the case, or if it
> > ever changes, we could always install a signal handler for SIGCONT that set the
> > flag before resuming the vm.
> >
> > Scheduling delays are also beyond the scope of this problem and I see the soft
> > lockup warning as appropriate in that case.
>
> I don't think you should see a guest softlockup if the host is
> overloaded. Nor should you see it due to a long live migration pause,
> or STOP/CONT. You should see a guest softlockup if it is spinning due
> to a guest bug, and not for any other reason.
>
> I think we need a mix of the ioctl (for STOP/CONT and voluntary pauses,
> like live migration or qemu stop/cont) and preempt notifiers (together
> with a check for TASK_RUNNING/TASK_UNINTERRUPTIBLE, for scheduling or
> swap delays)
>
> --
> error compiling committee.c: too many arguments to function
>

Do you want the preemption notifier work in before you will consider merging
this set, or can that be a follow on?

Eric
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