From: Ralf Baechle <ralf@linux-mips.org>
To: Dominic Sweetman <dom@mips.com>
Cc: Andrew Isaacson <adi@broadcom.com>, linux-mips@linux-mips.org
Subject: Re: [PATCH 8/12] cerr-printk-not-prom-printf
Date: Thu, 20 Oct 2005 12:17:11 +0100 [thread overview]
Message-ID: <20051020111711.GM2616@linux-mips.org> (raw)
In-Reply-To: <17239.31049.107570.828550@arsenal.mips.com>
On Thu, Oct 20, 2005 at 12:02:33PM +0100, Dominic Sweetman wrote:
> > 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'
> instruction.
But in case of the code in question no eret will be executed between taking
the cache error exception and printk trying to take the lock.
> 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
> system.
Fine - but at that point we could have two processors messing with the
same buffers. Bad Thing (TM).
Ralf
next prev parent reply other threads:[~2005-10-20 11:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-20 6:53 [PATCH 0/12] bcm1480 support Andrew Isaacson
2005-10-20 6:54 ` [PATCH 1/12] sibyte-fixes Andrew Isaacson
2005-10-20 6:55 ` [PATCH 2/12] 1480-headers Andrew Isaacson
2005-10-20 6:55 ` [PATCH 3/12] sibyte-header-cleanup Andrew Isaacson
2005-10-20 6:56 ` [PATCH 4/12] sb1a-support Andrew Isaacson
2005-10-20 6:56 ` [PATCH 5/12] 1480-support Andrew Isaacson
2005-10-20 6:57 ` [PATCH 6/12] bigsur-support Andrew Isaacson
2005-10-20 6:57 ` [PATCH 7/12] sb1-cache-exc-handling Andrew Isaacson
2005-10-20 6:57 ` [PATCH 8/12] cerr-printk-not-prom-printf Andrew Isaacson
2005-10-20 10:49 ` Ralf Baechle
2005-10-20 11:02 ` Dominic Sweetman
2005-10-20 11:17 ` Ralf Baechle [this message]
2005-10-20 6:58 ` [PATCH 9/12] sbmac-fixes Andrew Isaacson
2005-10-20 6:58 ` [PATCH 10/12] 1480-pci-support Andrew Isaacson
2005-10-20 6:59 ` [PATCH 11/12] 1480-ht-support Andrew Isaacson
2005-10-20 6:59 ` [PATCH 12/12] pci-expmem-hack Andrew Isaacson
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