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

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Message-ID: <20200822123252.GQ1362448@hirez.programming.kicks-ass.net>
Date:   Sat, 22 Aug 2020 14:32:52 +0200
From:   peterz@...radead.org
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     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 Fri, Aug 21, 2020 at 05:03:34PM -0400, Steven Rostedt wrote:

> > Sigh.  Is it too hard to make mutex_trylock() usable from interrupt
> > context?
> 
> 
> That's a question for Thomas and Peter Z.

You should really know that too, the TL;DR answer is it's fundamentally
buggered, can't work.

The problem is that RT relies on being able to PI boost the mutex owner.

ISTR we had a thread about all this last year or so, let me see if I can
find that.

Here goes:

  https://lkml.kernel.org/r/20191218135047.GS2844@hirez.programming.kicks-ass.net

Kexec even gets mentioned:

  https://lkml.kernel.org/r/20191219090535.GV2844@hirez.programming.kicks-ass.net