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

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Message-ID: <X/gmtIqgT27OvDX6@hirez.programming.kicks-ass.net>
Date:   Fri, 8 Jan 2021 10:32:36 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sebastian Siewior <bigeasy@...utronix.de>
Cc:     Ran Wang <ran.wang_1@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiafei Pan <jiafei.pan@....com>,
        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
Subject: Re: [PATCH] [RFC] rt: kernel/sched/core: fix kthread_park() pending
 too long when CPU un-plugged

On Thu, Jan 07, 2021 at 04:28:43PM +0100, Sebastian Siewior wrote:
> This sleep can be triggered by ptrace/strace() and with brief testing I
> can trigger the sleep there but I don't get it anywhere near where I
> would notice it with cyclictest.

It's a single task wakeup (the caller), doing that from hardirq context
really should not be a problem, we do lots of that in RT already.