On 12/08/2011 05:19 PM, Eric B Munson wrote:

quoted

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