linux-kernel - Re: [patch] mm, debug: allow suppressing panic on CONFIG_DEBUG

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Message-ID: <ZGxvOcmC8adflVcn@dhcp22.suse.cz>
Date:   Tue, 23 May 2023 09:46:01 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alex Shi <alexs@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Duyck <alexanderduyck@...com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, debug: allow suppressing panic on CONFIG_DEBUG_VM
 checks

On Mon 22-05-23 11:48:52, Linus Torvalds wrote:
> On Mon, May 22, 2023 at 11:39 AM David Rientjes <rientjes@...gle.com> wrote:
> >
> > I think VM_BUG_ON*() and friends are used to crash the kernel for
> > debugging so that we get a crash dump and because some variants don't
> > exist for VM_WARN_ON().
> 
> I do think that from a VM developer standpoint, I think it should be
> fine to just effectively turn VM_BUG_ON() into WARN_ON_ONCE() together
> with panic_on_warn.

This is a very good idea. VM_BUG_ON has always been rather special and
from my past experience people are not really sure when to use it. It is
a conditional thing so it cannot be really used for really BUG_ON cases.
Turning them into VM_WARN (not sure about ONCE) makes a lot of sense
because as you say you can make them panic easily.
-- 
Michal Hocko
SUSE Labs