Re: [External] Re: Fwd: WARNING: CPU: 13 PID: 3837105 at kernel/sched/sched.h:1561 __cfsb_csd_unthrottle+0x149/0x160

[Hao Jia <jiahao.os@bytedance.com>]

On 2023/9/5 Peter Zijlstra wrote:
> On Thu, Aug 31, 2023 at 04:48:29PM +0800, Hao Jia wrote:
> 
>> If I understand correctly, rq->clock_update_flags may be set to
>> RQCF_ACT_SKIP after __schedule() holds the rq lock, and sometimes the rq
>> lock may be released briefly in __schedule(), such as newidle_balance(). At
>> this time Other CPUs hold this rq lock, and then calling
>> rq_clock_start_loop_update() may trigger this warning.
>>
>> This warning check might be wrong. We need to add assert_clock_updated() to
>> check that the rq clock has been updated before calling
>> rq_clock_start_loop_update().
>>
>> Maybe some things can be like this?
> 
> Urgh, aside from it being white space mangled, I think this is entirely
> going in the wrong direction.
> 
> Leaking ACT_SKIP is dodgy as heck.. it's entirely too late to think
> clearly though, I'll have to try again tomorrow.

Hi Peter,

Do you think this fix method is correct? Or should we go back to the 
beginning and move update_rq_clock() from unthrottle_cfs_rq()?

Thanks,
Hao