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

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Message-ID: <5c3a502f-2255-5aae-3599-5220aa4b8328@jv-coder.de>
Date:   Mon, 7 Sep 2020 14:03:09 +0200
From:   Joerg Vehlow <lkml@...coder.de>
To:     peterz@...radead.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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>
Subject: Re: [BUG RT] dump-capture kernel not executed for panic in interrupt
 context

On 9/7/2020 1:46 PM, peterz@...radead.org wrote:
> I think it's too complicated for that is needed, did you see my
> suggestion from a year ago? Did i miss something obvious?
>
This one? 
https://lore.kernel.org/linux-fsdevel/20191219090535.GV2844@hirez.programming.kicks-ass.net/

I think it may be a bit incorrect?
According to the original comment in __crash_kexec, the mutex was used to
prevent a sys_kexec_load, while crash_kexec is executed. Your proposed 
patch
does not lock the mutex in crash_kexec. This does not cover the original 
use
case anymore. The only thing that is protected now are two panicing cores at
the same time.
Actually, this implementation feels even more hacky to me....

Jörg