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Date: Tue, 5 Sep 2023 00:23:51 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Hao Jia <jiahao.os@bytedance.com>
Cc: Benjamin Segall <bsegall@google.com>,
	Bagas Sanjaya <bagasdotme@gmail.com>,
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Subject: Re: [External] Re: Fwd: WARNING: CPU: 13 PID: 3837105 at
 kernel/sched/sched.h:1561 __cfsb_csd_unthrottle+0x149/0x160
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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.