Question on GCC 4.8 atomics

[Andrew Haley]

On 04/05/2013 02:04 PM, Bjorn Lindgren wrote:
> On Fri, 5 Apr 2013, Andrew Haley wrote:
> 
>>> Well, that was what I wanted to find out, do I need error handling if the
>>> event of a colliction (two cores exectuing CMPXCHG within the same clock
>>> cycles), the instruction will be automaticly retried until it succeeds?
>>
>> Correct.
>>
>>> Is that true for the x86 asm implementations of __atomic_*_fetch /
>>> __atomic_fetch_* calls too, that they are retried?
>>
>> Which x86 asm implementations do you mean?  We're talking about
>> GCC here, and it has builtins.
> 
> I was refering to the internal GCC implementation of the builtin 
> functions:
> 
> __atomic_add_fetch
> __atomic_sub_fetch 
> __atomic_and_fetch
> __atomic_xor_fetch
> etc..
> 
> I'd assume there is a separate assembler implementaion for each
> processor architecture (x86, SPARC, MIPS, ARM, etc).

Sometimes there isn't: they're usually builtins.  And they all block
until they succeed.

Andrew.