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

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Message-ID: <YtZa6YYnMPVUP345@localhost.localdomain>
Date:   Tue, 19 Jul 2022 09:19:05 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Ankit Jain <ankitja@...are.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 19/07/22 05:30, Ankit Jain wrote:
> 
> 
> > 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 for the details. Yeah, I should be able to set this up on my end.
It might just take a bit though, as I have some pto planned coming up.
But, I'll get to it eventually.

Thanks again,
Juri