> On Thu, Aug 21, 2008 at 01:02:48PM +0200, Peter Zijlstra wrote:
>> On Thu, 2008-08-21 at 12:57 +0200, Stefan Richter wrote:
>>> Peter Zijlstra wrote:
>>>> On Wed, 2008-08-20 at 20:50 -0600,
jmerkey@wolfmountaingroup.com wrote:
>>>>
>>>>> volatiles left in the code due to the previously stated
>>>>> (and still present) severe breakage of the GNU compiler with SMP
>>>>> shared data. most of the barrier() functions are just plain broken
>>>>> and do not result in proper compiler behavior in this tree.
>>>> Can you provide explicit detail?
>>>>
>>>> By using barrier() the compiler should clobber all its memory and
>>>> registers therefore forcing a write/reload of the variable.
>>> I hope Jeff didn't try mere barrier()s only. smp_wmb() and smp_rmb()
>>> are the more relevant barrier variants for mdb, from what I remember
>>> when I last looked at it.
>> Sure, but volatile isn't a replacement for memory barriers.
>
> Let's face it, the C standard does not support concurrency, so we are
> all in a state of sin in any case, forced to rely on combinations of
> gcc-specific non-standard language extensions and assembly language.
>
> Could be worse!!!
