Messages in this thread | | | Date | Wed, 14 Dec 2011 17:08:36 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host |
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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
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