linux-kernel - Re: [GIT PULL] slab fixes for 3.2-rc4

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Message-ID: <CA+55aFz23nN4EALZKf1uptn3a+LKU8wehEnxXO7WA8J5WAyPAQ@mail.gmail.com>
Date:	Tue, 29 Nov 2011 11:29:51 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Pekka Enberg <penberg@...nel.org>, Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [GIT PULL] slab fixes for 3.2-rc4

On Tue, Nov 29, 2011 at 10:02 AM, Pekka Enberg <penberg@...nel.org> wrote:
>
> The most important ones are from Christoph Lameter and Eric Dumazet that fix
> stability issues on non-x86 architectures.
>
> Christoph Lameter (1):
>      slub: use irqsafe_cpu_cmpxchg for put_cpu_partial

Quite frankly, I think "this_cpu_cmpxchg()" is pure crap, and this fix
was wrong, wrong, WRONG.

Dammit, the emulation is just bad.

The *only* architecture that implements "this_cpu_cmpxchg()" specially
seems to be x86.

So every other architecture uses the emulated one, AND THE EMULATED
ONE DOES NOT MATCH THE X86 SEMANTICS!

Sorry for shouting, but that's just *incredibly* stupid.

What's extra stupid is that s390 actually separately implements the
irq-safe version, and does it with code that seems to be generic, and
actually uses "cmpxchg()" like the regular "this_cpu_cmpxchg()" name
implies!

In other words, I would suggest that:

 - we get rid of that totally crazy idiotic "irqsafe" crap. The normal
one should be irq-safe. It's named "cmpxchg", for chrissake!

 - we make the non-arch-specific "this_cpu_cmpxchg()" use the correct
s390 routines instead of the pure and utter *shit* it uses now.

Yes, I'm upset. This "random percpu crap for SLUB" has been going on
too f*cking long, and it has been *continually* plagued by just pure
sh*t like this.

Seriously. Stop taking patches from Christoph in this area until they
have been vetted for sanity and completeness. This kind of ugly "let's
mis-name our functions in really subtle ways so that they work on x86
but nowhere else" needs to stop.

I pulled this crap because clearly it fixes a bug, but just stop it.
Show some TASTE!

                            Linus
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