Re: Race betwen the NMI handler and the RTC clock in practially allkernels II

[Maciej W. Rozycki]

On Mon, 25 Oct 2004, Andi Kleen wrote:

> So it's impossible to check the old value. The original code is the only
> way to do this (if it's even needed, Intel also doesn't say anything
> about this bit being a flip-flop). Only possible change would be to 
> write an alternative index.

 You can't read the old value, but you can have a shadow variable written
every time the real index is written.  Since NMIs are not preemptible and
this is a simple producer-consumer access, no mutex around accesses to the
variable is needed.

  Maciej
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