Re: [Xen-devel] [PATCH v3 2/5] build: Hook the schedulers into Kconfig

[Jonathan Creekmore <jonathan.creekmore@xxxxxxxxx>]

Doug Goldstein writes:

> On 1/8/16 10:49 AM, Jan Beulich wrote:
>>>>> On 08.01.16 at 17:30, <jonathan.creekmore@xxxxxxxxx> wrote:
>>> So, based on the Kconfig setup and the linker ASSERT, there should be no
>>> way to have a default scheduler that is not in the build. I wish Kconfig
>>> allowed you to state that you must have at least one option selected or
>>> up to all of the options selected (so I could require 1-4 schedulers
>>> compiled in, but not 0). Unfortunately, the only way that seems allowed
>>> is if you compile code in as modules, which Xen does not (with a choice
>>> block, you can select multiple items as M, but only 1 as Y, but at least
>>> 1 must be present --- since we only support Y, the choice block wouldn't
>>> work for the schedulers).
>>
>> Perhaps credit should just not be configurable then?
>>
>> Jan
>>
>
> How much effort are we willing to put in saving someone? We've already
> got these options completely hidden away. We've already given the user a
> warning that what they're doing isn't supported and they shouldn't be
> touching this. Then they have to disable the scheduler that they pick as
> the default. How many people are we expecting to really do this? I'm all
> for idiot proofing things but at some point we've got to say there's
> enough barriers to prevent this from happening. Otherwise we need to put
> a Xen developer in every Xen users home or office.

At this point, with the (not submitted yet) ASSERT in the linker file,
it is a compile error to not have any schedulers linked in and Kconfig
enforces that only schedulers compiled in can be a default.

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