Re: [Xen-devel] Wrong cpupool handling

[Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>]

Am Mittwoch 12 November 2014, 11:25:14 schrieb Juergen Gross:
> On 11/12/2014 10:53 AM, Dietmar Hahn wrote:
> > Am Dienstag 11 November 2014, 15:21:01 schrieb Juergen Gross:
> >> Hi again,
> >>
> >> On 11/11/2014 01:18 PM, Dietmar Hahn wrote:
> >>> Hi list,
> >>>
> >>> When creating a cpupool, starting and destroying a guest within this pool,
> >>> then removing this pool doesn't work because of EBUSY.
> >>>
> >>> It seems the cause of this behavior is the commit
> >>> bac6334b51d9bcfe57ecf4a4cb5288348fcf044a.
> >>>
> >>> In domain_kill() the function sched_move_domain() gets called changing the
> >>> d->cpupool pointer to the new cpupool without incrementing/decrementing 
> >>> the
> >>> counters "n_dom" of the new/old cpupool.
> >>>
> >>> This leads to decrementing the wrong  cpupool0->n_dom counter when
> >>> cpupool_rm_domain() gets called at the end and my own cpupool can't be
> >>> destroyed because n_dom = 1!
> >>>
> >>> I don't have a fast patch because I'am not enough familiar with the code
> >>> this time but I think it should be fixed for 4.5.
> >>
> >> Please discard previous patch, try this one.
> >
> > Yes this patch works.
> 
> Thanks. Can I add your "tested-by:"?

Sorry forgot it!

Tested-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>

> 
> > But I think in general a better solution would be to have the changing of 
> > the
> > cpupool pointer in sched_move_domain() together with the increment/decrement
> > of the counters but I see the locking problem.
> 
> The scheduler should never change cpupool owned data. The cpupool
> pointer is domain data, so changing this is okay.
> 
> 
> Juergen
> 
> 
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