linux-kernel - Re: [External] Re: [PATCH v5 2/4] sched/core: Avoid double calling update_rq_clock() in __balance_push_cpu

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Date:   Fri, 16 Jun 2023 11:18:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Hao Jia <jiahao.os@...edance.com>
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,
        mgorman@...hsingularity.net, linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH v5 2/4] sched/core: Avoid double calling
 update_rq_clock() in __balance_push_cpu_stop()

On Fri, Jun 16, 2023 at 03:56:25PM +0800, Hao Jia wrote:

> I'm afraid not, the rq clock also needs to be updated before
> select_fallback_rq() is called.

> If we just remove update_rq_clock() from __balance_push_cpu_stop(), we will
> get this warning.
> 
> 
> [ 1260.960166] rq->clock_update_flags < RQCF_ACT_SKIP
> [ 1260.960170] WARNING: CPU: 25 PID: 196 at kernel/sched/sched.h:1496
> update_curr+0xf6/0x1f0
> 
> [ 1260.960318] Call Trace:
> [ 1260.960320]  <TASK>
> [ 1260.960359]  dequeue_entity+0x3b/0x410
> [ 1260.960361]  dequeue_task_fair+0xc7/0x3c0
> [ 1260.960363]  dequeue_task+0x30/0xf0
> [ 1260.960365]  __do_set_cpus_allowed+0x94/0x130
> [ 1260.960366]  do_set_cpus_allowed+0x38/0x60
> [ 1260.960368]  cpuset_cpus_allowed_fallback+0x70/0x80
> [ 1260.960372]  select_fallback_rq+0x20f/0x250            <----

Urgh... :-(