RFR: 8187227: __m68k_cmpxchg() is not being used correctly

[John Paul Adrian Glaubitz]

On 11/18/2017 12:46 PM, Andrew Haley wrote:
>> Without seeing how that wrapper actually works, it is hard to know 
>> whether what you are saying and your fix is correct. The description of 
>> the CAS at [1] doesn't help without knowing how it actually gets used.
> 
> I can't see the point of the loops.

The loops are necessary because it's not guaranteed that the CAS instruction
will succeed at first attempt. You basically have to keep trying until it
succeeds. At least to my current knowledge.

The loops are already in the code, FWIW. I am just modifying the code because
the current code makes incorrect assumptions on how __m68k_cmpxchg() actually
works.

Adrian

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