Re: [Xen-devel] [PATCH for 4.5 v4 1/4] xen: add real time scheduler rtds

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Wed, Sep 24, 2014 at 2:41 PM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
> On mer, 2014-09-24 at 14:35 +0100, George Dunlap wrote:
>> On 09/24/2014 02:32 PM, Jan Beulich wrote:
>> >>>> On 24.09.14 at 15:14, <dario.faggioli@xxxxxxxxxx> wrote:
>> >> On mer, 2014-09-24 at 13:09 +0100, Jan Beulich wrote:
>> >>> Furthermore the function appears to lack serialization with other
>> >>> scheduler operations.
>> >>>
>> >> Not sure what you mean here. There's only one lock serializing
>> >> everything in this scheduler, and it's already taken when this is
>> >> called, the only exception being when it's called from rt_alloc_vdata().
>> >>
>> >> Is it that one you're referring to?
>> > No. The call path do_domctl() -> sched_adjust() -> rt_dom_cntl()
>> > doesn't take any scheduler related locks afaics.
>>
>> Indeed.
>>
> Yep.
>
> So, Meng, I think all we said in this thread makes sense:
>  - sanity checking input params in rt_dom_cntl()
>  - serialize rt_dom_cntl() itself against the global lock
>  - move the call to rt_update_deadline() from _alloc to _insert
>
> Probably in this priority order. :-)

And it's probably a good idea to do an audit: Go through every access
of svc->period, svc->budget, sdom, svcpu, &c in the file and check to
make sure that someone is holding the appropriate lock.

 -George

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