Re: [PATCH v2] arch/arm64: Fix topology initialization for core scheduling

[Dietmar Eggemann]

On 31/03/2022 15:21, Phil Auld wrote:
> On Thu, Mar 31, 2022 at 11:04:31AM +0200 Dietmar Eggemann wrote:
>> On 30/03/2022 17:56, Phil Auld wrote:

[...]

>> Ah, the reason is that smt_mask is not correctly setup, so we bail on
>> `cpumask_weight(smt_mask) == 1` for !leaders in:
>>
>> notify_cpu_starting()
>>   cpuhp_invoke_callback_range()
>>     sched_cpu_starting()
>>       sched_core_cpu_starting()
>>
>> which leads to rq->core not being correctly set for !leader-rq's.
>>
> 
> Exactly, sorry I was not clearer.  smt_mask must be setup correctly 
> by the time sched_core_cpu_starting() is called. (Maybe I should crib
> some of the above lines into the commit message?)

Yeah, maybe, it wouldn't hurt I guess. IMHO mentioning stress-ng's prctl
needs PR_SCHED_CORE support could also be handy since today's stress-ng
packages don't seem to have this yet.