linux-kernel - Re: [PATCH] [RFC] rt: kernel/sched/core: fix kthread_park() pending too long when CPU un-plugged

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Date:   Fri, 8 Jan 2021 10:05:06 +0100
From:   Sebastian Siewior <bigeasy@...utronix.de>
To:     Ran Wang <ran.wang_1@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiafei Pan <jiafei.pan@....com>,
        "linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        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>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC] rt: kernel/sched/core: fix kthread_park() pending
 too long when CPU un-plugged

On 2021-01-08 08:45:14 [+0000], Ran Wang wrote:
> Hi Sebastian, Peter
Hi,

> > I had a similar patch in -RT and dropped it in v5.10-rc7-rt16.
> > It was added because RT couldn't boot since creating the boot-threads didn't work before the ksoftirqd was up. This was fixed by commit
> >    26c7295be0c5e ("kthread: Do not preempt current task if it is going to call schedule()")
> 
> I tried applying above commit to linux-5.6.y-rt, it could resolve my problem on LX2160ARDB, THANKS!

so in other words all this could have been avoided by using a supported
or maintained RT series. The v5.4 series has this patch, v5.6 isn't
maintained anymore so it is likely that there is more missing.

Sebastian