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Re: Using __kuser_cmpxchg

On Thu, 15 Nov 2007, David Daney wrote:

> Nicolas Pitre wrote:
> > On Thu, 15 Nov 2007, David Daney wrote:
> > 
> > > This seems similar to MIPS ll/sc.  Perhaps if the arm port were modeled
> > > after
> > > that.
> > 
> > It is when available.  But the ARM ll/sc instructions are available only
> > from architecture level 6, hence not available on many others.
> > 
> 
> Similar issues exist with MIPS.  The MIPS Linux kernel emulates ll/sc via the
> illegal instruction trap if the cpu does not directly support it.
> 
> If the arm Linux port does (or was modified to do) likewise, we could then
> just always use the ldrex/strex.

And then performances go down the drain for what still corresponds to 
the majority of ARM platforms in the field.  No thanks.


Nicolas
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