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Date: Thu, 18 Feb 2010 11:58:01 +0100
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Message-ID: <ff13bc9a1002180258h667a96b2s611140fc3e2492be@mail.gmail.com>
Subject: Re: [PATCH 08/10] x86-32: support atomic64_t on 386/486 UP/SMP
From: Luca Barbieri <luca@luca-barbieri.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@elte.hu, hpa@zytor.com, akpm@linux-foundation.org,
       linux-kernel@vger.kernel.org
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> IIRC we dropped <i586 SMP support, and since we don't have a PMU on
> those chips atomic64_t doesn't need to be NMI safe, so a simple
> UP-IRQ-disable implementation should suffice.

We need the generic version with spinlocks for other architectures,
and reusing it is the cheapest way to support 386/486.

We thus get 386/486 SMP for free, and on UP the spinlocks simplify to
just IRQ disabling.

The only thing we could do is to #ifdef out the hashed spinlock array
in the generic implementation on UP builds, which would save about 1KB
of memory.
That is independent from this patch though.
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