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Re: [PATCH 8/12] cerr-printk-not-prom-printf

To: Ralf Baechle <>
Subject: Re: [PATCH 8/12] cerr-printk-not-prom-printf
From: Dominic Sweetman <>
Date: Thu, 20 Oct 2005 12:02:33 +0100
Cc: Andrew Isaacson <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <>
Ralf Baechle ( writes:

> The reason for this old commit was that this code is running
> uncached, so the operation of ll/sc in the spinlocks is undefined
> according to the MIPS64 spec...

The answer is more complicated.  MIPS64 (elsewhere) requires that the
ll/sc "link" is broken on an exceptin - in fact on an 'eret'

So ll/sc on an uncached location works just fine in a uniprocessor.  
However, it's unlikely that any cache-coherent mulitprocessor system
will snoop uncached reads and writes, so it won't work in an SMP


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