On Wed, Dec 14, 2011 at 04:39:56PM +0200, Avi Kivity wrote:

On 12/14/2011 02:16 PM, Marcelo Tosatti wrote:

quoted

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Having this controlled from userspace means it doesn't work for SIGSTOP
or for long scheduling delays.  What about doing this automatically
based on preempt notifiers?

Long scheduling delays should be considered hangups from the guest
perspective.

Why?  To the guest it looks like slow hardware, but it will interpret it
as a softlockup.

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.

quoted

About SIGSTOP, that is a corner case. Unsure if its even properly supported 
by QEMU.

It works from my experience.