[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 2/5] build: Hook the schedulers into Kconfig
On 08/01/16 17:04, Jonathan Creekmore wrote: > 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. I think that should be sufficient. A user has to go a long way out of their way to get into this situation in the first place. If there is a nice way for checking for an empty string in the preprocessor, then something like BUILD_BUG_ON(ARRAY_SIZE(CONFIG_SCHED_DEFAULT) == 1); would also be a good sanity check, but I doubt this specific example compiles. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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