Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 10 Nov 2022 01:48:32 +0200
From:   Aaro Koskinen <aaro.koskinen@iki.fi>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Paul Cercueil <paul@crapouillou.net>, vbabka@suse.cz,
        42.hyeyoo@gmail.com, akpm@linux-foundation.org,
        catalin.marinas@arm.com, cl@linux.com, iamjoonsoo.kim@lge.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        penberg@kernel.org, rientjes@google.com, rkovhaev@gmail.com,
        roman.gushchin@linux.dev, willy@infradead.org
Subject: Re: Deprecating and removing SLOB
Message-ID: <20221109234832.GE307514@darkstar.musicnaut.iki.fi>
References: <K5M3LR.3O50LSSSY5L3@crapouillou.net>
 <CAHk-=wjBqwJk9RgfoBuM00T49M7uQiLnOvLST7L6v5rhS7fkDA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAHk-=wjBqwJk9RgfoBuM00T49M7uQiLnOvLST7L6v5rhS7fkDA@mail.gmail.com>
Precedence: bulk

Hi,

On Wed, Nov 09, 2022 at 01:39:12PM -0800, Linus Torvalds wrote:
> On Wed, Nov 9, 2022 at 12:56 PM Paul Cercueil <paul@crapouillou.net> wrote:
> >
> > It worked fine on some boards, but on others it had about a 25% chance
> > of booting, and 75% chance of hanging at boot. I tried printk-debugging
> > it, and was coming to the conclusion that it's memory corruption of
> > some sort.
> >
> > Then I switched to SLUB and all the problems are gone. Same with SLAB.
> >
> > So while I can't say for sure that SLOB is broken (it might be
> > triggering a bug somewhere else), I am highly suspicious that it is.
> 
> I have this distinct memory of having seen other reports like this,
> but my google-fu is not strong enough to back that up.
> 
> There definitely has been recurring noise about SLOB issues. There's a
> reason people have wanted to remove it for years and years.

Some of the reported SLOB issues have been actually real driver bugs,
that go unnoticed when SLUB/SLAB are used (unless perhaps debug stuff
is enabled). I'm not saying kernel should keep SLUB, but it's good at
failing early when there is a bug. See e.g. commit 120ee599b5bf ("staging:
octeon-usb: prevent memory corruption")

A.