linux-kernel - Re: [External] Re: [PATCH] sched/core: Fix wrong warning check in rq_clock_start_loop

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Date:   Thu, 12 Oct 2023 17:04:51 +0800
From:   Hao Jia <jiahao.os@...edance.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, mingo@...nel.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Igor Raits <igor.raits@...il.com>,
        Bagas Sanjaya <bagasdotme@...il.com>
Subject: Re: [External] Re: [PATCH] sched/core: Fix wrong warning check in
 rq_clock_start_loop_update()



On 2023/10/10 Peter Zijlstra wrote:
> On Sat, Oct 07, 2023 at 04:44:46PM +0800, Hao Jia wrote:
> 
>>> That is, would not something like the below make more sense?
>>
>> If we understand correctly, this may not work.
>>
>> After applying this patch, the following situation will trigger the
>> rq->clock_update_flags < RQCF_ACT_SKIP warning.
>>
>> If rq_clock_skip_update() is called before __schedule(), so RQCF_REQ_SKIP of
>> rq->clock_update_flags is set.
>>
>>
>>
>>
>> __schedule() {
>> 	rq_lock(rq, &rf); [rq->clock_update_flags is RQCF_REQ_SKIP]
>> 	rq->clock_update_flags <<= 1;
>> 	update_rq_clock(rq); [rq->clock_update_flags is RQCF_ACT_SKIP]
>> + 	rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
>> 	* At this time, rq->clock_update_flags = 0; *
> 
> Fixed easily enough, just change to:
> 
> 	rq->clock_updated_flags = RQCF_UPDATED;
> 


Thanks for your suggestions and help, I revised the commit message and 
sent patch v2.

https://lore.kernel.org/all/20231012090003.11450-1-jiahao.os@bytedance.com/

Please review again.

Thanks,
Hao

>>
>>           pick_next_task_fair
>>           set_next_entity
>>           update_load_avg
>>           	assert_clock_updated() <---
>> }
>