linux-kernel - Re: [PATCH] siganl: ignore other signals when doing coredump

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Message-ID: <20200803191725.GA2078@redhat.com>
Date:   Mon, 3 Aug 2020 21:17:25 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "chunlei.wang" <Chunlei.wang@...iatek.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        linux-mediatek@...ts.infradead.org, wsd_upstream@...iatek.com,
        weiwei.zhang@...iatek.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] siganl: ignore other signals when doing coredump

On 07/31, chunlei.wang wrote:
>
> Please tell us much more about why you think Linux would benefit from
> this change.  Precisely what operational problems are you seeing with
> the current code?
> =>
>        Sorry for the late reply.
>
>        If coredump is incomplete, R&D can not find root cause through
> coredump.
>  If the issue is seldom, this modification will speed up the process of
> solving the problem.

To be honest, I do not even know what can I say, except that I disagree
with this change. The very idea looks wrong to me.

Granted, SIGKILL can kill the process which does something useful. Say,
dumps a core. So what?

Where does this SIGKILL come from? How often does this happen?

And why do you think the core dumping is special? Say, you try to debug
the buggy application, but a sudden SIGKILL kills the debuggee and you
lose the debugging session. Does this mean that the kernel needs another
patch to protect the process running under gdb from SIGKILL?

I don't think so. Please feel free to resend this patch, but it needs
a very convincing changelog. And please send it to lkml.

Oleg.