linux-kernel - Re: [PATCH 4/7] signal/mips: Document a conflict with SI

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Message-ID: <20170807195513.GD3509@linux-mips.org>
Date:   Mon, 7 Aug 2017 21:55:13 +0200
From:   Ralf Baechle <ralf@...ux-mips.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Maciej W. Rozycki" <macro@...tec.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Oleg Nesterov <oleg@...hat.com>,
        Andrei Vagin <avagin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>, Greg KH <greg@...ah.com>,
        Andrey Vagin <avagin@...nvz.org>,
        Serge Hallyn <serge@...lyn.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Willy Tarreau <w@....eu>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH 4/7] signal/mips: Document a conflict with SI_USER with
 SIGFPE

On Mon, Aug 07, 2017 at 10:41:39AM -0700, Linus Torvalds wrote:

> On Mon, Aug 7, 2017 at 9:18 AM, Maciej W. Rozycki <macro@...tec.com> wrote:
> >
> >  So what would be the right value of `si_code' to use here for such an
> > unexpected exception condition?  I think `BUG()' would be too big a
> > hammer here.  Or wouldn't it?
> 
> Hell no. NEVER EVER BUG().
> 
> The only case to use BUG() is if there is some core data structure
> (say, kernel stack) that is so corrupted that you know you cannot
> continue. That's the *only* valid use.
> 
> If this is a "this condition cannot happen" issue, then just remove
> the damn conditional. It's pointless. Adding a BUG() to show "this
> cannot happen" is not acceptable.

I queued a patch to remove the code for 4.14.

  Ralf