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    SubjectRe: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host
    On Mon, Dec 19, 2011 at 02:11:08PM -0200, Marcelo Tosatti wrote:
    > On Mon, Dec 19, 2011 at 02:59:10PM +0200, Avi Kivity wrote:
    > > On 12/16/2011 11:31 AM, Marcelo Tosatti wrote:
    > > > > >
    > > > > > Slow enough that progress of the watchdog thread is unable to keep up
    > > > > > with timer interrupt processing. This is considered a hang and
    > > > > > should be reported.
    > > > >
    > > > > It's not a guest hang though!
    > > >
    > > > No, but your host system is in such a load state that for the sake of
    > > > system usability you better print out a warning message.
    > >
    > > What's the point in printing it in the guest? The guest can't observe
    > > host conditions.
    > >
    > > > I don't see the advantage of preempt notifiers over the simple, paravirt
    > > > solution proposed? Note kvmclock is already paravirt.
    > >
    > > Right.
    > >
    > > > What do you want to be done in preempt notifiers? Measure what to
    > > > consider setting this flag?
    > >
    > > Preemption while TASK_RUNNING or TASK_UNINTERRUPTIBLE.
    >
    > Maybe it is good (not sure), need to look into schedstats and think of
    > cases that would break legitimate guest hangs. And it probably also
    > affects the position of clearing the flag on the guest side as its
    > currently done in Eric's patchset.

    Is the task going to be TASK_UNINTERRUPTIBLE with SIGSTOP? Don't think
    so.

    Note "Preemption while TASK_RUNNING or TASK_UNINTERRUPTIBLE" is not
    functional for guest-paused-via-QEMU-monitor case.



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