linux-kernel - Re: [BUG RT] dump-capture kernel not executed for panic in interrupt context

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Date:   Mon, 07 Sep 2020 13:49:53 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     peterz@...radead.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Vehlow <lkml@...coder.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Huang Ying <ying.huang@...el.com>,
        linux-kernel@...r.kernel.org,
        Joerg Vehlow <joerg.vehlow@...-tech.de>, dave@...olabs.net
Subject: Re: [BUG RT] dump-capture kernel not executed for panic in interrupt context


On 07/09/20 12:41, peterz@...radead.org wrote:
> So cenceptually there's the problem that idle must always be runnable,
> and the moment you boost it, it becomes subject to a different
> scheduling class.
>
> Imagine for example what happens when we boost it to RT and then have it
> be subject to throttling. What are we going to run when the idle task
> is no longer elegible to run.
>
> (it might all work out by accident, but ISTR we had a whole bunch of fun
> in the earlier days of RT due to things like that)

Doesn't that become a non-problem (conceptually) with proxy exec? In that
case the idle task remains forever runnable, it just runs with its own
scheduling context during the throttling window.

Not trying to sell PE as the Billy Mays-backed solution to all kernel
issues, but I think it's another thing for me to ponder on & play with.