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Date: Sat, 09 Dec 2000 19:11:57 +0100
To: "David S. Miller" <davem@redhat.com>
From: Roberto Fichera <kernel@tekno-soft.it>
Subject: Re: [PATCH] mm->rss is modified without page_table_lock held
Cc: rasmus@jaquet.dk, torvalds@transmeta.com, linux-kernel@vger.kernel.org
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At 07.00 09/12/00 -0800, David S. Miller wrote:

>    Date: Sat, 09 Dec 2000 16:07:03 +0100
>    From: Roberto Fichera <kernel@tekno-soft.it>
>
>    8 bits for a spinlock ? What kind of use we have here ?
>
>Sparc32 (like some other older architectures) do not have a
>word atomic update instruction, but it does have a byte spinlock.
>To conserve space and implement the atomic update properly, we
>use a spinlock in the top byte of the word.

There's any possibility ;-) to define it as

typedef struct { volatile char spinlock, volatile long counter } atomic_t;

>Also, this sematic was decided upon many eons ago, changing it a month
>before 2.4.0 just to deal with this mm->rss atomicity issue is not
>going to happen.  The spinlock patch exists, and if nothing better
>comes up, we should just use it.

Indeed! You are right! I was thinking to optimize it, using a 
spinlock/unlock we spent
several time for a inc.

Roberto Fichera.

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