linux-kernel - Re: [PATCH] sched/deadline: Fix BUG

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Message-ID: <B466E709-EFCF-4B27-B3F6-D7561C381BF7@vmware.com>
Date:   Tue, 19 Jul 2022 05:30:16 +0000
From:   Ankit Jain <ankitja@...are.com>
To:     Juri Lelli <juri.lelli@...hat.com>
CC:     "srivatsa@...il.mit.edu" <srivatsa@...il.mit.edu>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Sharan Turlapati <sturlapati@...are.com>,
        Him Kalyan Bordoloi <bordoloih@...are.com>,
        Keerthana Kalyanasundaram <keerthanak@...are.com>,
        Anish Swaminathan <anishs@...are.com>,
        Srivatsa Bhat <srivatsab@...are.com>
Subject: Re: [PATCH] sched/deadline: Fix BUG_ON condition for deboosted tasks



> On 18-Jul-2022, at 6:31 PM, Juri Lelli <juri.lelli@...hat.com> wrote:
> 
> ⚠ External Email
> 
> On 18/07/22 07:46, Ankit Jain wrote:
> 
> ...
> 
>> Hi Juri,
>> 
>> Actually, while testing I already included below commits in 4.19-rt :
>> 
>> feff2e65efd8d84cf831668e182b2ce73c604bbb (sched/deadline: Unthrottle PI boosted threads while
>> enqueuing)
>> 46fcc4b00c3cca8adb9b7c9afdd499f64e427135 (sched/deadline: Fix stale throttling on de-/boosted tasks)
>> 2279f540ea7d05f22d2f0c4224319330228586bc (sched/deadline: Fix priority inheritance with multiple)
>> 0e3872499de1a1230cef5221607d71aa09264bd5 (kernel/sched: Remove dl_boosted flag comment)
> 
> Interesting.
> 
> Is the workload you are using to test this easily reproducible? I'd like
> to try that out on my end to check if I see the same (of course the
> issue I was working on goes away with my fix :).
> 
> Best,
> Juri
> 

Hi Juri,

The test with which i am able to hit the issue is as follows:
	• Schedule SCHED_FIFO/55 (sched_priority = 55) tasks running infinite loop on all isolated cores.
	• spwan 30-40 docker containers in loop (docker load , docker run)
	• Immediately after that schedule SCHED_FIFO/55 (sched_priority = 55) tasks running infinite loop on all isolated cores again.
	• BUG_ON gets hit almost every time.
System config as follows:
	• 4.19-rt kernel
	• 40 cpu (0-1 housekeeping, 2-39 isol cpus)
	• stalld-1.3.0 with the fixes from latest version (for task starvation avoidance), "tuned" with real-time profile 

Thanks.