Re: [PATCH -tip] sched/fair: gracefully handle EEVDF scheduling failures

[Tiwei Bie]

On 12/8/23 10:32 PM, Peter Zijlstra wrote:
> On Fri, Dec 08, 2023 at 07:20:59PM +0800, Tiwei Bie wrote:
>> The EEVDF scheduling might fail due to unforeseen issues. Previously,
> 
> I might also fly if I jump up. But is there any actual reason to believe
> something like that will happen?

Thanks for the quick reply! Sorry, after re-reading the commit log,
it looks confusing to me as well. I didn't mean something like that
will happen. I just thought it might be worthwhile to have a sanity
check on 'best'. Because, the 'best' is initialized to NULL and is
conditionally updated. The added 'WARN_ONCE' on '!best' is more like
a 'default' case to catch an unreachable case in a 'switch' block.
There was a similar check in the past that was helpful. And there
seems to be no harm in doing it. If this is reasonable, I'd like to
submit a v2 patch.

PS. I just noticed that the subject line should start with a uppercase
letter according to the rules in the tip tree handbook [1]. The subject
line should be something like: "sched/fair: Sanity check best in pick_eevdf()".

[1] https://www.kernel.org/doc/html/next/process/maintainer-tip.html#patch-subject

Regards,
Tiwei