icedtea zero ARM atomic patch

[Andrew Haley]

Gary Benson wrote:
> Xerxes Rånby wrote:
>> Here is a patch for the ARM zero port to deal with missing atomic
>> operations in the ARM hardware, here implemented using linux-
>> kernelcalls.  With this patch the zero hotspot and bootstrap-ecj
>> part of icedtea6 do compile on ARM targets.
> 
> I committed a reworked version of the first part of this patch.
> I've left the second part out as I don't think it's used -- you'll
> get an "unimplemented" message if it is.
> 
> FWIW I'm not entirely convinced that the arm-specific functions
> are doing what they ought; arm_add_and_fetch and arm_lock_test_and_set
> seem to be dereferencing a volatile pointer twice, which doesn't seem
> atomic to me.  But then I'm not great at this stuff either :)

I committed my versions of these functions.  I'm convinced they're
correct, but the ARM zero port still isn't stable.  I think the
problem must lie elsewhere, but I'm not sure what it might be.

Andrew.