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Date: Tue, 28 Jun 2005 15:34:43 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: "David S. Miller" <davem@davemloft.net>
CC: wli@holomorphy.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch 2] mm: speculative get_page
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David S. Miller wrote:

>From: Nick Piggin <nickpiggin@yahoo.com.au>
>Subject: Re: [patch 2] mm: speculative get_page
>Date: Tue, 28 Jun 2005 14:50:31 +1000
>
>
>>William Lee Irwin III wrote:
>>
>>
>>>On Tue, Jun 28, 2005 at 11:42:16AM +1000, Nick Piggin wrote:
>>>
>>>spin_unlock() does not imply a memory barrier.
>>>
>>>
>>Intriguing...
>>
>
>BTW, I disagree with this assertion.  spin_unlock() does imply a
>memory barrier.
>
>All memory operations before the release of the lock must execute
>before the lock release memory operation is globally visible.
>

Yes, it appears that way from looking at a sample set of arch
code too (ie. those without strictly ordered stores put an
explicit barrier there).

I've always understood spin_unlock to imply a barrier.


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