From: Chris Metcalf <cmetcalf@tilera.com>
To: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@linux-foundation.org>,
Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [PATCH] slub: always align cpu_slab to honor cmpxchg_double requirement
Date: Thu, 2 Jun 2011 14:13:00 -0400 [thread overview]
Message-ID: <4DE7D2AC.1070503@tilera.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1106021015220.18350@chino.kir.corp.google.com>
On 6/2/2011 1:16 PM, David Rientjes wrote:
> On Thu, 2 Jun 2011, Chris Metcalf wrote:
>> On an architecture without CMPXCHG_LOCAL but with DEBUG_VM enabled,
>> the VM_BUG_ON() in __pcpu_double_call_return_bool() will cause an early
>> panic during boot unless we always align cpu_slab properly.
>>
>> In principle we could remove the alignment-testing VM_BUG_ON() for
>> architectures that don't have CMPXCHG_LOCAL, but leaving it in means
>> that new code will tend not to break x86 even if it is introduced
>> on another platform, and it's low cost to require alignment.
>>
>> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
> Acked-by: David Rientjes <rientjes@google.com>
>
>> ---
>> This needs to be pushed for 3.0 to allow arch/tile to boot.
>> I'm happy to push it but I assume it would be better coming
>> from an mm or percpu tree. Thanks!
>>
> Should also be marked for stable for 2.6.39.x, right?
No, in 2.6.39 the irqsafe_cpu_cmpxchg_double() was guarded under "#ifdef
CONFIG_CMPXCHG_LOCAL". Now it's not. I suppose we could take the comment
change in percpu.h for 2.6.39, but it probably doesn't merit churning the
stable tree.
--
Chris Metcalf, Tilera Corp.
http://www.tilera.com
WARNING: multiple messages have this Message-ID (diff)
From: Chris Metcalf <cmetcalf@tilera.com>
To: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@linux-foundation.org>,
Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] slub: always align cpu_slab to honor cmpxchg_double requirement
Date: Thu, 2 Jun 2011 14:13:00 -0400 [thread overview]
Message-ID: <4DE7D2AC.1070503@tilera.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1106021015220.18350@chino.kir.corp.google.com>
On 6/2/2011 1:16 PM, David Rientjes wrote:
> On Thu, 2 Jun 2011, Chris Metcalf wrote:
>> On an architecture without CMPXCHG_LOCAL but with DEBUG_VM enabled,
>> the VM_BUG_ON() in __pcpu_double_call_return_bool() will cause an early
>> panic during boot unless we always align cpu_slab properly.
>>
>> In principle we could remove the alignment-testing VM_BUG_ON() for
>> architectures that don't have CMPXCHG_LOCAL, but leaving it in means
>> that new code will tend not to break x86 even if it is introduced
>> on another platform, and it's low cost to require alignment.
>>
>> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
> Acked-by: David Rientjes <rientjes@google.com>
>
>> ---
>> This needs to be pushed for 3.0 to allow arch/tile to boot.
>> I'm happy to push it but I assume it would be better coming
>> from an mm or percpu tree. Thanks!
>>
> Should also be marked for stable for 2.6.39.x, right?
No, in 2.6.39 the irqsafe_cpu_cmpxchg_double() was guarded under "#ifdef
CONFIG_CMPXCHG_LOCAL". Now it's not. I suppose we could take the comment
change in percpu.h for 2.6.39, but it probably doesn't merit churning the
stable tree.
--
Chris Metcalf, Tilera Corp.
http://www.tilera.com
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next prev parent reply other threads:[~2011-06-02 18:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-02 14:19 [PATCH] slub: always align cpu_slab to honor cmpxchg_double requirement Chris Metcalf
2011-06-02 14:19 ` Chris Metcalf
2011-06-02 17:16 ` David Rientjes
2011-06-02 17:16 ` David Rientjes
2011-06-02 18:13 ` Chris Metcalf [this message]
2011-06-02 18:13 ` Chris Metcalf
2011-06-03 5:49 ` Pekka Enberg
2011-06-03 5:49 ` Pekka Enberg
2011-06-03 14:06 ` Christoph Lameter
2011-06-03 14:33 ` Chris Metcalf
2011-06-03 14:33 ` Chris Metcalf
2011-06-03 14:41 ` Christoph Lameter
2011-06-03 14:41 ` Christoph Lameter
2011-06-03 18:06 ` Pekka Enberg
2011-06-03 18:06 ` Pekka Enberg
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