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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Pekka Enberg <penberg@kernel.org>, Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Christoph Lameter <cl@linux.com>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [GIT PULL] slab fixes for 3.2-rc4
Date: Tue, 29 Nov 2011 11:29:51 -0800	[thread overview]
Message-ID: <CA+55aFz23nN4EALZKf1uptn3a+LKU8wehEnxXO7WA8J5WAyPAQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1111292001420.4019@tux.localdomain>

On Tue, Nov 29, 2011 at 10:02 AM, Pekka Enberg <penberg@kernel.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

  reply	other threads:[~2011-11-29 19:30 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-11-29 18:02 [GIT PULL] slab fixes for 3.2-rc4 Pekka Enberg
2011-11-29 19:29 ` Linus Torvalds [this message]
2011-11-29 19:38   ` Linus Torvalds
2011-12-20  9:47   ` Pekka Enberg
2011-12-20 16:23     ` Tejun Heo
2011-12-20 16:31       ` Christoph Lameter
2011-12-20 19:28       ` Linus Torvalds
2011-12-20 20:28         ` Tejun Heo
2011-12-21  8:08           ` Pekka Enberg
2011-12-21 17:09             ` Tejun Heo
2011-12-21 15:16           ` Christoph Lameter
2011-12-21 17:05             ` Tejun Heo
2011-12-22  2:19               ` Linus Torvalds
2011-12-22 16:05                 ` Tejun Heo
2011-12-28 10:25                 ` Benjamin Herrenschmidt
2011-12-22 14:58               ` Christoph Lameter
2011-12-22 16:08                 ` Tejun Heo
2011-12-22 17:58                   ` Christoph Lameter
2011-12-22 18:03                     ` Ingo Molnar
2011-12-22 18:31                     ` Linus Torvalds
2011-12-23 16:55                       ` Christoph Lameter
2011-12-23 20:54                         ` Linus Torvalds
2012-01-04 15:30                           ` Christoph Lameter
2012-01-04 16:07                             ` Linus Torvalds
2012-01-04 17:00                               ` Christoph Lameter
2012-01-04 23:10                                 ` Linus Torvalds
2012-01-05 19:15                                   ` Christoph Lameter
2012-01-05 19:27                                     ` Linus Torvalds
2011-12-22 18:47                     ` Tejun Heo
2011-12-20 16:26     ` Christoph Lameter
2011-12-21  8:06       ` Pekka Enberg
2011-12-21 15:20         ` Christoph Lameter

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