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Subject: Re: [PATCH] Linux Kernel Markers
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Helge Hafting <helge.hafting@aitel.hist.no>
Cc: prasanna@in.ibm.com, Martin Bligh <mbligh@google.com>,
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Ar Mer, 2006-09-20 am 11:39 +0200, ysgrifennodd Helge Hafting:
> Yes, 5 bytes is not an atomic write except on 64-bit. So a race is possible.

Untrue as well. Pentium and later have CMPXCHG8.

> How about this workaround:
> 1. Overwrite the start of the function with a hlt, which is atomic.
> 2. Write that 5-byte jump after the hlt.
> 3. Overwrite the hlt with nop so things will work
> 4. interrupt any cpus that got stuck on the hlt - or just wait for the 
> timer.

CPU errata time again. You have to synchronize.

Alan

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