Re: [Xen-devel] Using debug-key 'o: Dump IOMMU p2m table, locks up machine

[Santosh Jodh <Santosh.Jodh@xxxxxxxxxx>]

> -----Original Message-----
> From: Keir Fraser [mailto:keir.xen@xxxxxxxxx]
> Sent: Saturday, September 01, 2012 12:13 PM
> To: Santosh Jodh; Sander Eikelenboom
> Cc: wei.wang2@xxxxxxx; xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Using debug-key 'o: Dump IOMMU p2m table, locks
> up machine
> 
> On 01/09/2012 18:03, "Santosh Jodh" <Santosh.Jodh@xxxxxxxxxx> wrote:
> 
> >> It might schedule softirqs but that won't include scheduling or
> >> running any guest vcpus. The vcpu that happens to be running on that
> >> cpu at the time the debug dump starts, will be stuck unrunnable until the
> dump completes.
> >
> > Why does'nt that vCPU get scheduled on some other pCPU? Is there  a
> > way to yield the CPU from the key handler?
> 
> It can't be descheduled from this pCPU without running through the
> scheduler. You could try running the handler in a tasklet -- a tasklet causes
> other vCPUs to be descheduled from that pCPU, before it starts running.
> 
> So you'd register a keyhandler which does a tasklet_schedule(), and do your
> logging work in the tasklet handler.
> 
> Worth a shot maybe?

Yes - certainly. Is there a reason why all key handlers should not be tasklets?


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